summaryrefslogtreecommitdiffstats
path: root/drivers/platform/surface/aggregator/controller.c
blob: 69e86cd599d38dce783d91b061ab5d3d6dbdf10b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
// SPDX-License-Identifier: GPL-2.0+
/*
 * Main SSAM/SSH controller structure and functionality.
 *
 * Copyright (C) 2019-2020 Maximilian Luz <luzmaximilian@gmail.com>
 */

#include <linux/acpi.h>
#include <linux/atomic.h>
#include <linux/completion.h>
#include <linux/gpio/consumer.h>
#include <linux/interrupt.h>
#include <linux/kref.h>
#include <linux/limits.h>
#include <linux/list.h>
#include <linux/lockdep.h>
#include <linux/mutex.h>
#include <linux/rculist.h>
#include <linux/rbtree.h>
#include <linux/rwsem.h>
#include <linux/serdev.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/srcu.h>
#include <linux/types.h>
#include <linux/workqueue.h>

#include <linux/surface_aggregator/controller.h>
#include <linux/surface_aggregator/serial_hub.h>

#include "controller.h"
#include "ssh_msgb.h"
#include "ssh_request_layer.h"

#include "trace.h"


/* -- Safe counters. -------------------------------------------------------- */

/**
 * ssh_seq_reset() - Reset/initialize sequence ID counter.
 * @c: The counter to reset.
 */
static void ssh_seq_reset(struct ssh_seq_counter *c)
{
	WRITE_ONCE(c->value, 0);
}

/**
 * ssh_seq_next() - Get next sequence ID.
 * @c: The counter providing the sequence IDs.
 *
 * Return: Returns the next sequence ID of the counter.
 */
static u8 ssh_seq_next(struct ssh_seq_counter *c)
{
	u8 old = READ_ONCE(c->value);
	u8 new = old + 1;
	u8 ret;

	while (unlikely((ret = cmpxchg(&c->value, old, new)) != old)) {
		old = ret;
		new = old + 1;
	}

	return old;
}

/**
 * ssh_rqid_reset() - Reset/initialize request ID counter.
 * @c: The counter to reset.
 */
static void ssh_rqid_reset(struct ssh_rqid_counter *c)
{
	WRITE_ONCE(c->value, 0);
}

/**
 * ssh_rqid_next() - Get next request ID.
 * @c: The counter providing the request IDs.
 *
 * Return: Returns the next request ID of the counter, skipping any reserved
 * request IDs.
 */
static u16 ssh_rqid_next(struct ssh_rqid_counter *c)
{
	u16 old = READ_ONCE(c->value);
	u16 new = ssh_rqid_next_valid(old);
	u16 ret;

	while (unlikely((ret = cmpxchg(&c->value, old, new)) != old)) {
		old = ret;
		new = ssh_rqid_next_valid(old);
	}

	return old;
}


/* -- Event notifier/callbacks. --------------------------------------------- */
/*
 * The notifier system is based on linux/notifier.h, specifically the SRCU
 * implementation. The difference to that is, that some bits of the notifier
 * call return value can be tracked across multiple calls. This is done so
 * that handling of events can be tracked and a warning can be issued in case
 * an event goes unhandled. The idea of that warning is that it should help
 * discover and identify new/currently unimplemented features.
 */

/**
 * ssam_event_matches_notifier() - Test if an event matches a notifier.
 * @n: The event notifier to test against.
 * @event: The event to test.
 *
 * Return: Returns %true if the given event matches the given notifier
 * according to the rules set in the notifier's event mask, %false otherwise.
 */
static bool ssam_event_matches_notifier(const struct ssam_event_notifier *n,
					const struct ssam_event *event)
{
	bool match = n->event.id.target_category == event->target_category;

	if (n->event.mask & SSAM_EVENT_MASK_TARGET)
		match &= n->event.reg.target_id == event->target_id;

	if (n->event.mask & SSAM_EVENT_MASK_INSTANCE)
		match &= n->event.id.instance == event->instance_id;

	return match;
}

/**
 * ssam_nfblk_call_chain() - Call event notifier callbacks of the given chain.
 * @nh:    The notifier head for which the notifier callbacks should be called.
 * @event: The event data provided to the callbacks.
 *
 * Call all registered notifier callbacks in order of their priority until
 * either no notifier is left or a notifier returns a value with the
 * %SSAM_NOTIF_STOP bit set. Note that this bit is automatically set via
 * ssam_notifier_from_errno() on any non-zero error value.
 *
 * Return: Returns the notifier status value, which contains the notifier
 * status bits (%SSAM_NOTIF_HANDLED and %SSAM_NOTIF_STOP) as well as a
 * potential error value returned from the last executed notifier callback.
 * Use ssam_notifier_to_errno() to convert this value to the original error
 * value.
 */
static int ssam_nfblk_call_chain(struct ssam_nf_head *nh, struct ssam_event *event)
{
	struct ssam_event_notifier *nf;
	int ret = 0, idx;

	idx = srcu_read_lock(&nh->srcu);

	list_for_each_entry_rcu(nf, &nh->head, base.node,
				srcu_read_lock_held(&nh->srcu)) {
		if (ssam_event_matches_notifier(nf, event)) {
			ret = (ret & SSAM_NOTIF_STATE_MASK) | nf->base.fn(nf, event);
			if (ret & SSAM_NOTIF_STOP)
				break;
		}
	}

	srcu_read_unlock(&nh->srcu, idx);
	return ret;
}

/**
 * ssam_nfblk_insert() - Insert a new notifier block into the given notifier
 * list.
 * @nh: The notifier head into which the block should be inserted.
 * @nb: The notifier block to add.
 *
 * Note: This function must be synchronized by the caller with respect to other
 * insert, find, and/or remove calls by holding ``struct ssam_nf.lock``.
 *
 * Return: Returns zero on success, %-EEXIST if the notifier block has already
 * been registered.
 */
static int ssam_nfblk_insert(struct ssam_nf_head *nh, struct ssam_notifier_block *nb)
{
	struct ssam_notifier_block *p;
	struct list_head *h;

	/* Runs under lock, no need for RCU variant. */
	list_for_each(h, &nh->head) {
		p = list_entry(h, struct ssam_notifier_block, node);

		if (unlikely(p == nb)) {
			WARN(1, "double register detected");
			return -EEXIST;
		}

		if (nb->priority > p->priority)
			break;
	}

	list_add_tail_rcu(&nb->node, h);
	return 0;
}

/**
 * ssam_nfblk_find() - Check if a notifier block is registered on the given
 * notifier head.
 * list.
 * @nh: The notifier head on which to search.
 * @nb: The notifier block to search for.
 *
 * Note: This function must be synchronized by the caller with respect to other
 * insert, find, and/or remove calls by holding ``struct ssam_nf.lock``.
 *
 * Return: Returns true if the given notifier block is registered on the given
 * notifier head, false otherwise.
 */
static bool ssam_nfblk_find(struct ssam_nf_head *nh, struct ssam_notifier_block *nb)
{
	struct ssam_notifier_block *p;

	/* Runs under lock, no need for RCU variant. */
	list_for_each_entry(p, &nh->head, node) {
		if (p == nb)
			return true;
	}

	return false;
}

/**
 * ssam_nfblk_remove() - Remove a notifier block from its notifier list.
 * @nb: The notifier block to be removed.
 *
 * Note: This function must be synchronized by the caller with respect to
 * other insert, find, and/or remove calls by holding ``struct ssam_nf.lock``.
 * Furthermore, the caller _must_ ensure SRCU synchronization by calling
 * synchronize_srcu() with ``nh->srcu`` after leaving the critical section, to
 * ensure that the removed notifier block is not in use any more.
 */
static void ssam_nfblk_remove(struct ssam_notifier_block *nb)
{
	list_del_rcu(&nb->node);
}

/**
 * ssam_nf_head_init() - Initialize the given notifier head.
 * @nh: The notifier head to initialize.
 */
static int ssam_nf_head_init(struct ssam_nf_head *nh)
{
	int status;

	status = init_srcu_struct(&nh->srcu);
	if (status)
		return status;

	INIT_LIST_HEAD(&nh->head);
	return 0;
}

/**
 * ssam_nf_head_destroy() - Deinitialize the given notifier head.
 * @nh: The notifier head to deinitialize.
 */
static void ssam_nf_head_destroy(struct ssam_nf_head *nh)
{
	cleanup_srcu_struct(&nh->srcu);
}


/* -- Event/notification registry. ------------------------------------------ */

/**
 * struct ssam_nf_refcount_key - Key used for event activation reference
 * counting.
 * @reg: The registry via which the event is enabled/disabled.
 * @id:  The ID uniquely describing the event.
 */
struct ssam_nf_refcount_key {
	struct ssam_event_registry reg;
	struct ssam_event_id id;
};

/**
 * struct ssam_nf_refcount_entry - RB-tree entry for reference counting event
 * activations.
 * @node:     The node of this entry in the rb-tree.
 * @key:      The key of the event.
 * @refcount: The reference-count of the event.
 * @flags:    The flags used when enabling the event.
 */
struct ssam_nf_refcount_entry {
	struct rb_node node;
	struct ssam_nf_refcount_key key;
	int refcount;
	u8 flags;
};

/**
 * ssam_nf_refcount_inc() - Increment reference-/activation-count of the given
 * event.
 * @nf:  The notifier system reference.
 * @reg: The registry used to enable/disable the event.
 * @id:  The event ID.
 *
 * Increments the reference-/activation-count associated with the specified
 * event type/ID, allocating a new entry for this event ID if necessary. A
 * newly allocated entry will have a refcount of one.
 *
 * Note: ``nf->lock`` must be held when calling this function.
 *
 * Return: Returns the refcount entry on success. Returns an error pointer
 * with %-ENOSPC if there have already been %INT_MAX events of the specified
 * ID and type registered, or %-ENOMEM if the entry could not be allocated.
 */
static struct ssam_nf_refcount_entry *
ssam_nf_refcount_inc(struct ssam_nf *nf, struct ssam_event_registry reg,
		     struct ssam_event_id id)
{
	struct ssam_nf_refcount_entry *entry;
	struct ssam_nf_refcount_key key;
	struct rb_node **link = &nf->refcount.rb_node;
	struct rb_node *parent = NULL;
	int cmp;

	lockdep_assert_held(&nf->lock);

	key.reg = reg;
	key.id = id;

	while (*link) {
		entry = rb_entry(*link, struct ssam_nf_refcount_entry, node);
		parent = *link;

		cmp = memcmp(&key, &entry->key, sizeof(key));
		if (cmp < 0) {
			link = &(*link)->rb_left;
		} else if (cmp > 0) {
			link = &(*link)->rb_right;
		} else if (entry->refcount < INT_MAX) {
			entry->refcount++;
			return entry;
		} else {
			WARN_ON(1);
			return ERR_PTR(-ENOSPC);
		}
	}

	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
	if (!entry)
		return ERR_PTR(-ENOMEM);

	entry->key = key;
	entry->refcount = 1;

	rb_link_node(&entry->node, parent, link);
	rb_insert_color(&entry->node, &nf->refcount);

	return entry;
}

/**
 * ssam_nf_refcount_dec() - Decrement reference-/activation-count of the given
 * event.
 * @nf:  The notifier system reference.
 * @reg: The registry used to enable/disable the event.
 * @id:  The event ID.
 *
 * Decrements the reference-/activation-count of the specified event,
 * returning its entry. If the returned entry has a refcount of zero, the
 * caller is responsible for freeing it using kfree().
 *
 * Note: ``nf->lock`` must be held when calling this function.
 *
 * Return: Returns the refcount entry on success or %NULL if the entry has not
 * been found.
 */
static struct ssam_nf_refcount_entry *
ssam_nf_refcount_dec(struct ssam_nf *nf, struct ssam_event_registry reg,
		     struct ssam_event_id id)
{
	struct ssam_nf_refcount_entry *entry;
	struct ssam_nf_refcount_key key;
	struct rb_node *node = nf->refcount.rb_node;
	int cmp;

	lockdep_assert_held(&nf->lock);

	key.reg = reg;
	key.id = id;

	while (node) {
		entry = rb_entry(node, struct ssam_nf_refcount_entry, node);

		cmp = memcmp(&key, &entry->key, sizeof(key));
		if (cmp < 0) {
			node = node->rb_left;
		} else if (cmp > 0) {
			node = node->rb_right;
		} else {
			entry->refcount--;
			if (entry->refcount == 0)
				rb_erase(&entry->node, &nf->refcount);

			return entry;
		}
	}

	return NULL;
}

/**
 * ssam_nf_refcount_empty() - Test if the notification system has any
 * enabled/active events.
 * @nf: The notification system.
 */
static bool ssam_nf_refcount_empty(struct ssam_nf *nf)
{
	return RB_EMPTY_ROOT(&nf->refcount);
}

/**
 * ssam_nf_call() - Call notification callbacks for the provided event.
 * @nf:    The notifier system
 * @dev:   The associated device, only used for logging.
 * @rqid:  The request ID of the event.
 * @event: The event provided to the callbacks.
 *
 * Execute registered callbacks in order of their priority until either no
 * callback is left or a callback returns a value with the %SSAM_NOTIF_STOP
 * bit set. Note that this bit is set automatically when converting non-zero
 * error values via ssam_notifier_from_errno() to notifier values.
 *
 * Also note that any callback that could handle an event should return a value
 * with bit %SSAM_NOTIF_HANDLED set, indicating that the event does not go
 * unhandled/ignored. In case no registered callback could handle an event,
 * this function will emit a warning.
 *
 * In case a callback failed, this function will emit an error message.
 */
static void ssam_nf_call(struct ssam_nf *nf, struct device *dev, u16 rqid,
			 struct ssam_event *event)
{
	struct ssam_nf_head *nf_head;
	int status, nf_ret;

	if (!ssh_rqid_is_event(rqid)) {
		dev_warn(dev, "event: unsupported rqid: %#06x\n", rqid);
		return;
	}

	nf_head = &nf->head[ssh_rqid_to_event(rqid)];
	nf_ret = ssam_nfblk_call_chain(nf_head, event);
	status = ssam_notifier_to_errno(nf_ret);

	if (status < 0) {
		dev_err(dev,
			"event: error handling event: %d (tc: %#04x, tid: %#04x, cid: %#04x, iid: %#04x)\n",
			status, event->target_category, event->target_id,
			event->command_id, event->instance_id);
	} else if (!(nf_ret & SSAM_NOTIF_HANDLED)) {
		dev_warn(dev,
			 "event: unhandled event (rqid: %#04x, tc: %#04x, tid: %#04x, cid: %#04x, iid: %#04x)\n",
			 rqid, event->target_category, event->target_id,
			 event->command_id, event->instance_id);
	}
}

/**
 * ssam_nf_init() - Initialize the notifier system.
 * @nf: The notifier system to initialize.
 */
static int ssam_nf_init(struct ssam_nf *nf)
{
	int i, status;

	for (i = 0; i < SSH_NUM_EVENTS; i++) {
		status = ssam_nf_head_init(&nf->head[i]);
		if (status)
			break;
	}

	if (status) {
		while (i--)
			ssam_nf_head_destroy(&nf->head[i]);

		return status;
	}

	mutex_init(&nf->lock);
	return 0;
}

/**
 * ssam_nf_destroy() - Deinitialize the notifier system.
 * @nf: The notifier system to deinitialize.
 */
static void ssam_nf_destroy(struct ssam_nf *nf)
{
	int i;

	for (i = 0; i < SSH_NUM_EVENTS; i++)
		ssam_nf_head_destroy(&nf->head[i]);

	mutex_destroy(&nf->lock);
}


/* -- Event/async request completion system. -------------------------------- */

#define SSAM_CPLT_WQ_NAME	"ssam_cpltq"

/*
 * SSAM_CPLT_WQ_BATCH - Maximum number of event item completions executed per
 * work execution. Used to prevent livelocking of the workqueue. Value chosen
 * via educated guess, may be adjusted.
 */
#define SSAM_CPLT_WQ_BATCH	10

/*
 * SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN - Maximum payload length for a cached
 * &struct ssam_event_item.
 *
 * This length has been chosen to be accommodate standard touchpad and
 * keyboard input events. Events with larger payloads will be allocated
 * separately.
 */
#define SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN	32

static struct kmem_cache *ssam_event_item_cache;

/**
 * ssam_event_item_cache_init() - Initialize the event item cache.
 */
int ssam_event_item_cache_init(void)
{
	const unsigned int size = sizeof(struct ssam_event_item)
				  + SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN;
	const unsigned int align = __alignof__(struct ssam_event_item);
	struct kmem_cache *cache;

	cache = kmem_cache_create("ssam_event_item", size, align, 0, NULL);
	if (!cache)
		return -ENOMEM;

	ssam_event_item_cache = cache;
	return 0;
}

/**
 * ssam_event_item_cache_destroy() - Deinitialize the event item cache.
 */
void ssam_event_item_cache_destroy(void)
{
	kmem_cache_destroy(ssam_event_item_cache);
	ssam_event_item_cache = NULL;
}

static void __ssam_event_item_free_cached(struct ssam_event_item *item)
{
	kmem_cache_free(ssam_event_item_cache, item);
}

static void __ssam_event_item_free_generic(struct ssam_event_item *item)
{
	kfree(item);
}

/**
 * ssam_event_item_free() - Free the provided event item.
 * @item: The event item to free.
 */
static void ssam_event_item_free(struct ssam_event_item *item)
{
	trace_ssam_event_item_free(item);
	item->ops.free(item);
}

/**
 * ssam_event_item_alloc() - Allocate an event item with the given payload size.
 * @len:   The event payload length.
 * @flags: The flags used for allocation.
 *
 * Allocate an event item with the given payload size, preferring allocation
 * from the event item cache if the payload is small enough (i.e. smaller than
 * %SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN). Sets the item operations and payload
 * length values. The item free callback (``ops.free``) should not be
 * overwritten after this call.
 *
 * Return: Returns the newly allocated event item.
 */
static struct ssam_event_item *ssam_event_item_alloc(size_t len, gfp_t flags)
{
	struct ssam_event_item *item;

	if (len <= SSAM_EVENT_ITEM_CACHE_PAYLOAD_LEN) {
		item = kmem_cache_alloc(ssam_event_item_cache, flags);
		if (!item)
			return NULL;

		item->ops.free = __ssam_event_item_free_cached;
	} else {
		item = kzalloc(struct_size(item, event.data, len), flags);
		if (!item)
			return NULL;

		item->ops.free = __ssam_event_item_free_generic;
	}

	item->event.length = len;

	trace_ssam_event_item_alloc(item, len);
	return item;
}

/**
 * ssam_event_queue_push() - Push an event item to the event queue.
 * @q:    The event queue.
 * @item: The item to add.
 */
static void ssam_event_queue_push(struct ssam_event_queue *q,
				  struct ssam_event_item *item)
{
	spin_lock(&q->lock);
	list_add_tail(&item->node, &q->head);
	spin_unlock(&q->lock);
}

/**
 * ssam_event_queue_pop() - Pop the next event item from the event queue.
 * @q: The event queue.
 *
 * Returns and removes the next event item from the queue. Returns %NULL If
 * there is no event item left.
 */
static struct ssam_event_item *ssam_event_queue_pop(struct ssam_event_queue *q)
{
	struct ssam_event_item *item;

	spin_lock(&q->lock);
	item = list_first_entry_or_null(&q->head, struct ssam_event_item, node);
	if (item)
		list_del(&item->node);
	spin_unlock(&q->lock);

	return item;
}

/**
 * ssam_event_queue_is_empty() - Check if the event queue is empty.
 * @q: The event queue.
 */
static bool ssam_event_queue_is_empty(struct ssam_event_queue *q)
{
	bool empty;

	spin_lock(&q->lock);
	empty = list_empty(&q->head);
	spin_unlock(&q->lock);

	return empty;
}

/**
 * ssam_cplt_get_event_queue() - Get the event queue for the given parameters.
 * @cplt: The completion system on which to look for the queue.
 * @tid:  The target ID of the queue.
 * @rqid: The request ID representing the event ID for which to get the queue.
 *
 * Return: Returns the event queue corresponding to the event type described
 * by the given parameters. If the request ID does not represent an event,
 * this function returns %NULL. If the target ID is not supported, this
 * function will fall back to the default target ID (``tid = 1``).
 */
static
struct ssam_event_queue *ssam_cplt_get_event_queue(struct ssam_cplt *cplt,
						   u8 tid, u16 rqid)
{
	u16 event = ssh_rqid_to_event(rqid);
	u16 tidx = ssh_tid_to_index(tid);

	if (!ssh_rqid_is_event(rqid)) {
		dev_err(cplt->dev, "event: unsupported request ID: %#06x\n", rqid);
		return NULL;
	}

	if (!ssh_tid_is_valid(tid)) {
		dev_warn(cplt->dev, "event: unsupported target ID: %u\n", tid);
		tidx = 0;
	}

	return &cplt->event.target[tidx].queue[event];
}

/**
 * ssam_cplt_submit() - Submit a work item to the completion system workqueue.
 * @cplt: The completion system.
 * @work: The work item to submit.
 */
static bool ssam_cplt_submit(struct ssam_cplt *cplt, struct work_struct *work)
{
	return queue_work(cplt->wq, work);
}

/**
 * ssam_cplt_submit_event() - Submit an event to the completion system.
 * @cplt: The completion system.
 * @item: The event item to submit.
 *
 * Submits the event to the completion system by queuing it on the event item
 * queue and queuing the respective event queue work item on the completion
 * workqueue, which will eventually complete the event.
 *
 * Return: Returns zero on success, %-EINVAL if there is no event queue that
 * can handle the given event item.
 */
static int ssam_cplt_submit_event(struct ssam_cplt *cplt,
				  struct ssam_event_item *item)
{
	struct ssam_event_queue *evq;

	evq = ssam_cplt_get_event_queue(cplt, item->event.target_id, item->rqid);
	if (!evq)
		return -EINVAL;

	ssam_event_queue_push(evq, item);
	ssam_cplt_submit(cplt, &evq->work);
	return 0;
}

/**
 * ssam_cplt_flush() - Flush the completion system.
 * @cplt: The completion system.
 *
 * Flush the completion system by waiting until all currently submitted work
 * items have been completed.
 *
 * Note: This function does not guarantee that all events will have been
 * handled once this call terminates. In case of a larger number of
 * to-be-completed events, the event queue work function may re-schedule its
 * work item, which this flush operation will ignore.
 *
 * This operation is only intended to, during normal operation prior to
 * shutdown, try to complete most events and requests to get them out of the
 * system while the system is still fully operational. It does not aim to
 * provide any guarantee that all of them have been handled.
 */
static void ssam_cplt_flush(struct ssam_cplt *cplt)
{
	flush_workqueue(cplt->wq);
}

static void ssam_event_queue_work_fn(struct work_struct *work)
{
	struct ssam_event_queue *queue;
	struct ssam_event_item *item;
	struct ssam_nf *nf;
	struct device *dev;
	unsigned int iterations = SSAM_CPLT_WQ_BATCH;

	queue = container_of(work, struct ssam_event_queue, work);
	nf = &queue->cplt->event.notif;
	dev = queue->cplt->dev;

	/* Limit number of processed events to avoid livelocking. */
	do {
		item = ssam_event_queue_pop(queue);
		if (!item)
			return;

		ssam_nf_call(nf, dev, item->rqid, &item->event);
		ssam_event_item_free(item);
	} while (--iterations);

	if (!ssam_event_queue_is_empty(queue))
		ssam_cplt_submit(queue->cplt, &queue->work);
}

/**
 * ssam_event_queue_init() - Initialize an event queue.
 * @cplt: The completion system on which the queue resides.
 * @evq:  The event queue to initialize.
 */
static void ssam_event_queue_init(struct ssam_cplt *cplt,
				  struct ssam_event_queue *evq)
{
	evq->cplt = cplt;
	spin_lock_init(&evq->lock);
	INIT_LIST_HEAD(&evq->head);
	INIT_WORK(&evq->work, ssam_event_queue_work_fn);
}

/**
 * ssam_cplt_init() - Initialize completion system.
 * @cplt: The completion system to initialize.
 * @dev:  The device used for logging.
 */
static int ssam_cplt_init(struct ssam_cplt *cplt, struct device *dev)
{
	struct ssam_event_target *target;
	int status, c, i;

	cplt->dev = dev;

	cplt->wq = create_workqueue(SSAM_CPLT_WQ_NAME);
	if (!cplt->wq)
		return -ENOMEM;

	for (c = 0; c < ARRAY_SIZE(cplt->event.target); c++) {
		target = &cplt->event.target[c];

		for (i = 0; i < ARRAY_SIZE(target->queue); i++)
			ssam_event_queue_init(cplt, &target->queue[i]);
	}

	status = ssam_nf_init(&cplt->event.notif);
	if (status)
		destroy_workqueue(cplt->wq);

	return status;
}

/**
 * ssam_cplt_destroy() - Deinitialize the completion system.
 * @cplt: The completion system to deinitialize.
 *
 * Deinitialize the given completion system and ensure that all pending, i.e.
 * yet-to-be-completed, event items and requests have been handled.
 */
static void ssam_cplt_destroy(struct ssam_cplt *cplt)
{
	/*
	 * Note: destroy_workqueue ensures that all currently queued work will
	 * be fully completed and the workqueue drained. This means that this
	 * call will inherently also free any queued ssam_event_items, thus we
	 * don't have to take care of that here explicitly.
	 */
	destroy_workqueue(cplt->wq);
	ssam_nf_destroy(&cplt->event.notif);
}


/* -- Main SSAM device structures. ------------------------------------------ */

/**
 * ssam_controller_device() - Get the &struct device associated with this
 * controller.
 * @c: The controller for which to get the device.
 *
 * Return: Returns the &struct device associated with this controller,
 * providing its lower-level transport.
 */
struct device *ssam_controller_device(struct ssam_controller *c)
{
	return ssh_rtl_get_device(&c->rtl);
}
EXPORT_SYMBOL_GPL(ssam_controller_device);

static void __ssam_controller_release(struct kref *kref)
{
	struct ssam_controller *ctrl = to_ssam_controller(kref, kref);

	/*
	 * The lock-call here is to satisfy lockdep. At this point we really
	 * expect this to be the last remaining reference to the controller.
	 * Anything else is a bug.
	 */
	ssam_controller_lock(ctrl);
	ssam_controller_destroy(ctrl);
	ssam_controller_unlock(ctrl);

	kfree(ctrl);
}

/**
 * ssam_controller_get() - Increment reference count of controller.
 * @c: The controller.
 *
 * Return: Returns the controller provided as input.
 */
struct ssam_controller *ssam_controller_get(struct ssam_controller *c)
{
	if (c)
		kref_get(&c->kref);
	return c;
}
EXPORT_SYMBOL_GPL(ssam_controller_get);

/**
 * ssam_controller_put() - Decrement reference count of controller.
 * @c: The controller.
 */
void ssam_controller_put(struct ssam_controller *c)
{
	if (c)
		kref_put(&c->kref, __ssam_controller_release);
}
EXPORT_SYMBOL_GPL(ssam_controller_put);

/**
 * ssam_controller_statelock() - Lock the controller against state transitions.
 * @c: The controller to lock.
 *
 * Lock the controller against state transitions. Holding this lock guarantees
 * that the controller will not transition between states, i.e. if the
 * controller is in state "started", when this lock has been acquired, it will
 * remain in this state at least until the lock has been released.
 *
 * Multiple clients may concurrently hold this lock. In other words: The
 * ``statelock`` functions represent the read-lock part of a r/w-semaphore.
 * Actions causing state transitions of the controller must be executed while
 * holding the write-part of this r/w-semaphore (see ssam_controller_lock()
 * and ssam_controller_unlock() for that).
 *
 * See ssam_controller_stateunlock() for the corresponding unlock function.
 */
void ssam_controller_statelock(struct ssam_controller *c)
{
	down_read(&c->lock);
}
EXPORT_SYMBOL_GPL(ssam_controller_statelock);

/**
 * ssam_controller_stateunlock() - Unlock controller state transitions.
 * @c: The controller to unlock.
 *
 * See ssam_controller_statelock() for the corresponding lock function.
 */
void ssam_controller_stateunlock(struct ssam_controller *c)
{
	up_read(&c->lock);
}
EXPORT_SYMBOL_GPL(ssam_controller_stateunlock);

/**
 * ssam_controller_lock() - Acquire the main controller lock.
 * @c: The controller to lock.
 *
 * This lock must be held for any state transitions, including transition to
 * suspend/resumed states and during shutdown. See ssam_controller_statelock()
 * for more details on controller locking.
 *
 * See ssam_controller_unlock() for the corresponding unlock function.
 */
void ssam_controller_lock(struct ssam_controller *c)
{
	down_write(&c->lock);
}

/*
 * ssam_controller_unlock() - Release the main controller lock.
 * @c: The controller to unlock.
 *
 * See ssam_controller_lock() for the corresponding lock function.
 */
void ssam_controller_unlock(struct ssam_controller *c)
{
	up_write(&c->lock);
}

static void ssam_handle_event(struct ssh_rtl *rtl,
			      const struct ssh_command *cmd,
			      const struct ssam_span *data)
{
	struct ssam_controller *ctrl = to_ssam_controller(rtl, rtl);
	struct ssam_event_item *item;

	item = ssam_event_item_alloc(data->len, GFP_KERNEL);
	if (!item)
		return;

	item->rqid = get_unaligned_le16(&cmd->rqid);
	item->event.target_category = cmd->tc;
	item->event.target_id = cmd->tid_in;
	item->event.command_id = cmd->cid;
	item->event.instance_id = cmd->iid;
	memcpy(&item->event.data[0], data->ptr, data->len);

	if (WARN_ON(ssam_cplt_submit_event(&ctrl->cplt, item)))
		ssam_event_item_free(item);
}

static const struct ssh_rtl_ops ssam_rtl_ops = {
	.handle_event = ssam_handle_event,
};

static bool ssam_notifier_is_empty(struct ssam_controller *ctrl);
static void ssam_notifier_unregister_all(struct ssam_controller *ctrl);

#define SSAM_SSH_DSM_REVISION	0

/* d5e383e1-d892-4a76-89fc-f6aaae7ed5b5 */
static const guid_t SSAM_SSH_DSM_GUID =
	GUID_INIT(0xd5e383e1, 0xd892, 0x4a76,
		  0x89, 0xfc, 0xf6, 0xaa, 0xae, 0x7e, 0xd5, 0xb5);

enum ssh_dsm_fn {
	SSH_DSM_FN_SSH_POWER_PROFILE             = 0x05,
	SSH_DSM_FN_SCREEN_ON_SLEEP_IDLE_TIMEOUT  = 0x06,
	SSH_DSM_FN_SCREEN_OFF_SLEEP_IDLE_TIMEOUT = 0x07,
	SSH_DSM_FN_D3_CLOSES_HANDLE              = 0x08,
	SSH_DSM_FN_SSH_BUFFER_SIZE               = 0x09,
};

static int ssam_dsm_get_functions(acpi_handle handle, u64 *funcs)
{
	union acpi_object *obj;
	u64 mask = 0;
	int i;

	*funcs = 0;

	/*
	 * The _DSM function is only present on newer models. It is not
	 * present on 5th and 6th generation devices (i.e. up to and including
	 * Surface Pro 6, Surface Laptop 2, Surface Book 2).
	 *
	 * If the _DSM is not present, indicate that no function is supported.
	 * This will result in default values being set.
	 */
	if (!acpi_has_method(handle, "_DSM"))
		return 0;

	obj = acpi_evaluate_dsm_typed(handle, &SSAM_SSH_DSM_GUID,
				      SSAM_SSH_DSM_REVISION, 0, NULL,
				      ACPI_TYPE_BUFFER);
	if (!obj)
		return -EIO;

	for (i = 0; i < obj->buffer.length && i < 8; i++)
		mask |= (((u64)obj->buffer.pointer[i]) << (i * 8));

	if (mask & BIT(0))
		*funcs = mask;

	ACPI_FREE(obj);
	return 0;
}

static int ssam_dsm_load_u32(acpi_handle handle, u64 funcs, u64 func, u32 *ret)
{
	union acpi_object *obj;
	u64 val;

	if (!(funcs & BIT_ULL(func)))
		return 0; /* Not supported, leave *ret at its default value */

	obj = acpi_evaluate_dsm_typed(handle, &SSAM_SSH_DSM_GUID,
				      SSAM_SSH_DSM_REVISION, func, NULL,
				      ACPI_TYPE_INTEGER);
	if (!obj)
		return -EIO;

	val = obj->integer.value;
	ACPI_FREE(obj);

	if (val > U32_MAX)
		return -ERANGE;

	*ret = val;
	return 0;
}

/**
 * ssam_controller_caps_load_from_acpi() - Load controller capabilities from
 * ACPI _DSM.
 * @handle: The handle of the ACPI controller/SSH device.
 * @caps:   Where to store the capabilities in.
 *
 * Initializes the given controller capabilities with default values, then
 * checks and, if the respective _DSM functions are available, loads the
 * actual capabilities from the _DSM.
 *
 * Return: Returns zero on success, a negative error code on failure.
 */
static
int ssam_controller_caps_load_from_acpi(acpi_handle handle,
					struct ssam_controller_caps *caps)
{
	u32 d3_closes_handle = false;
	u64 funcs;
	int status;

	/* Set defaults. */
	caps->ssh_power_profile = U32_MAX;
	caps->screen_on_sleep_idle_timeout = U32_MAX;
	caps->screen_off_sleep_idle_timeout = U32_MAX;
	caps->d3_closes_handle = false;
	caps->ssh_buffer_size = U32_MAX;

	/* Pre-load supported DSM functions. */
	status = ssam_dsm_get_functions(handle, &funcs);
	if (status)
		return status;

	/* Load actual values from ACPI, if present. */
	status = ssam_dsm_load_u32(handle, funcs, SSH_DSM_FN_SSH_POWER_PROFILE,
				   &caps->ssh_power_profile);
	if (status)
		return status;

	status = ssam_dsm_load_u32(handle, funcs,
				   SSH_DSM_FN_SCREEN_ON_SLEEP_IDLE_TIMEOUT,
				   &caps->screen_on_sleep_idle_timeout);
	if (status)
		return status;

	status = ssam_dsm_load_u32(handle, funcs,
				   SSH_DSM_FN_SCREEN_OFF_SLEEP_IDLE_TIMEOUT,
				   &caps->screen_off_sleep_idle_timeout);
	if (status)
		return status;

	status = ssam_dsm_load_u32(handle, funcs, SSH_DSM_FN_D3_CLOSES_HANDLE,
				   &d3_closes_handle);
	if (status)
		return status;

	caps->d3_closes_handle = !!d3_closes_handle;

	status = ssam_dsm_load_u32(handle, funcs, SSH_DSM_FN_SSH_BUFFER_SIZE,
				   &caps->ssh_buffer_size);
	if (status)
		return status;

	return 0;
}

/**
 * ssam_controller_init() - Initialize SSAM controller.
 * @ctrl:   The controller to initialize.
 * @serdev: The serial device representing the underlying data transport.
 *
 * Initializes the given controller. Does neither start receiver nor
 * transmitter threads. After this call, the controller has to be hooked up to
 * the serdev core separately via &struct serdev_device_ops, relaying calls to
 * ssam_controller_receive_buf() and ssam_controller_write_wakeup(). Once the
 * controller has been hooked up, transmitter and receiver threads may be
 * started via ssam_controller_start(). These setup steps need to be completed
 * before controller can be used for requests.
 */
int ssam_controller_init(struct ssam_controller *ctrl,
			 struct serdev_device *serdev)
{
	acpi_handle handle = ACPI_HANDLE(&serdev->dev);
	int status;

	init_rwsem(&ctrl->lock);
	kref_init(&ctrl->kref);

	status = ssam_controller_caps_load_from_acpi(handle, &ctrl->caps);
	if (status)
		return status;

	dev_dbg(&serdev->dev,
		"device capabilities:\n"
		"  ssh_power_profile:             %u\n"
		"  ssh_buffer_size:               %u\n"
		"  screen_on_sleep_idle_timeout:  %u\n"
		"  screen_off_sleep_idle_timeout: %u\n"
		"  d3_closes_handle:              %u\n",
		ctrl->caps.ssh_power_profile,
		ctrl->caps.ssh_buffer_size,
		ctrl->caps.screen_on_sleep_idle_timeout,
		ctrl->caps.screen_off_sleep_idle_timeout,
		ctrl->caps.d3_closes_handle);

	ssh_seq_reset(&ctrl->counter.seq);
	ssh_rqid_reset(&ctrl->counter.rqid);

	/* Initialize event/request completion system. */
	status = ssam_cplt_init(&ctrl->cplt, &serdev->dev);
	if (status)
		return status;

	/* Initialize request and packet transport layers. */
	status = ssh_rtl_init(&ctrl->rtl, serdev, &ssam_rtl_ops);
	if (status) {
		ssam_cplt_destroy(&ctrl->cplt);
		return status;
	}

	/*
	 * Set state via write_once even though we expect to be in an
	 * exclusive context, due to smoke-testing in
	 * ssam_request_sync_submit().
	 */
	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_INITIALIZED);
	return 0;
}

/**
 * ssam_controller_start() - Start the receiver and transmitter threads of the
 * controller.
 * @ctrl: The controller.
 *
 * Note: When this function is called, the controller should be properly
 * hooked up to the serdev core via &struct serdev_device_ops. Please refer
 * to ssam_controller_init() for more details on controller initialization.
 *
 * This function must be called with the main controller lock held (i.e. by
 * calling ssam_controller_lock()).
 */
int ssam_controller_start(struct ssam_controller *ctrl)
{
	int status;

	lockdep_assert_held_write(&ctrl->lock);

	if (ctrl->state != SSAM_CONTROLLER_INITIALIZED)
		return -EINVAL;

	status = ssh_rtl_start(&ctrl->rtl);
	if (status)
		return status;

	/*
	 * Set state via write_once even though we expect to be locked/in an
	 * exclusive context, due to smoke-testing in
	 * ssam_request_sync_submit().
	 */
	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_STARTED);
	return 0;
}

/*
 * SSAM_CTRL_SHUTDOWN_FLUSH_TIMEOUT - Timeout for flushing requests during
 * shutdown.
 *
 * Chosen to be larger than one full request timeout, including packets timing
 * out. This value should give ample time to complete any outstanding requests
 * during normal operation and account for the odd package timeout.
 */
#define SSAM_CTRL_SHUTDOWN_FLUSH_TIMEOUT	msecs_to_jiffies(5000)

/**
 * ssam_controller_shutdown() - Shut down the controller.
 * @ctrl: The controller.
 *
 * Shuts down the controller by flushing all pending requests and stopping the
 * transmitter and receiver threads. All requests submitted after this call
 * will fail with %-ESHUTDOWN. While it is discouraged to do so, this function
 * is safe to use in parallel with ongoing request submission.
 *
 * In the course of this shutdown procedure, all currently registered
 * notifiers will be unregistered. It is, however, strongly recommended to not
 * rely on this behavior, and instead the party registering the notifier
 * should unregister it before the controller gets shut down, e.g. via the
 * SSAM bus which guarantees client devices to be removed before a shutdown.
 *
 * Note that events may still be pending after this call, but, due to the
 * notifiers being unregistered, these events will be dropped when the
 * controller is subsequently destroyed via ssam_controller_destroy().
 *
 * This function must be called with the main controller lock held (i.e. by
 * calling ssam_controller_lock()).
 */
void ssam_controller_shutdown(struct ssam_controller *ctrl)
{
	enum ssam_controller_state s = ctrl->state;
	int status;

	lockdep_assert_held_write(&ctrl->lock);

	if (s == SSAM_CONTROLLER_UNINITIALIZED || s == SSAM_CONTROLLER_STOPPED)
		return;

	/*
	 * Try to flush pending events and requests while everything still
	 * works. Note: There may still be packets and/or requests in the
	 * system after this call (e.g. via control packets submitted by the
	 * packet transport layer or flush timeout / failure, ...). Those will
	 * be handled with the ssh_rtl_shutdown() call below.
	 */
	status = ssh_rtl_flush(&ctrl->rtl, SSAM_CTRL_SHUTDOWN_FLUSH_TIMEOUT);
	if (status) {
		ssam_err(ctrl, "failed to flush request transport layer: %d\n",
			 status);
	}

	/* Try to flush all currently completing requests and events. */
	ssam_cplt_flush(&ctrl->cplt);

	/*
	 * We expect all notifiers to have been removed by the respective client
	 * driver that set them up at this point. If this warning occurs, some
	 * client driver has not done that...
	 */
	WARN_ON(!ssam_notifier_is_empty(ctrl));

	/*
	 * Nevertheless, we should still take care of drivers that don't behave
	 * well. Thus disable all enabled events, unregister all notifiers.
	 */
	ssam_notifier_unregister_all(ctrl);

	/*
	 * Cancel remaining requests. Ensure no new ones can be queued and stop
	 * threads.
	 */
	ssh_rtl_shutdown(&ctrl->rtl);

	/*
	 * Set state via write_once even though we expect to be locked/in an
	 * exclusive context, due to smoke-testing in
	 * ssam_request_sync_submit().
	 */
	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_STOPPED);
	ctrl->rtl.ptl.serdev = NULL;
}

/**
 * ssam_controller_destroy() - Destroy the controller and free its resources.
 * @ctrl: The controller.
 *
 * Ensures that all resources associated with the controller get freed. This
 * function should only be called after the controller has been stopped via
 * ssam_controller_shutdown(). In general, this function should not be called
 * directly. The only valid place to call this function directly is during
 * initialization, before the controller has been fully initialized and passed
 * to other processes. This function is called automatically when the
 * reference count of the controller reaches zero.
 *
 * This function must be called with the main controller lock held (i.e. by
 * calling ssam_controller_lock()).
 */
void ssam_controller_destroy(struct ssam_controller *ctrl)
{
	lockdep_assert_held_write(&ctrl->lock);

	if (ctrl->state == SSAM_CONTROLLER_UNINITIALIZED)
		return;

	WARN_ON(ctrl->state != SSAM_CONTROLLER_STOPPED);

	/*
	 * Note: New events could still have been received after the previous
	 * flush in ssam_controller_shutdown, before the request transport layer
	 * has been shut down. At this point, after the shutdown, we can be sure
	 * that no new events will be queued. The call to ssam_cplt_destroy will
	 * ensure that those remaining are being completed and freed.
	 */

	/* Actually free resources. */
	ssam_cplt_destroy(&ctrl->cplt);
	ssh_rtl_destroy(&ctrl->rtl);

	/*
	 * Set state via write_once even though we expect to be locked/in an
	 * exclusive context, due to smoke-testing in
	 * ssam_request_sync_submit().
	 */
	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_UNINITIALIZED);
}

/**
 * ssam_controller_suspend() - Suspend the controller.
 * @ctrl: The controller to suspend.
 *
 * Marks the controller as suspended. Note that display-off and D0-exit
 * notifications have to be sent manually before transitioning the controller
 * into the suspended state via this function.
 *
 * See ssam_controller_resume() for the corresponding resume function.
 *
 * Return: Returns %-EINVAL if the controller is currently not in the
 * "started" state.
 */
int ssam_controller_suspend(struct ssam_controller *ctrl)
{
	ssam_controller_lock(ctrl);

	if (ctrl->state != SSAM_CONTROLLER_STARTED) {
		ssam_controller_unlock(ctrl);
		return -EINVAL;
	}

	ssam_dbg(ctrl, "pm: suspending controller\n");

	/*
	 * Set state via write_once even though we're locked, due to
	 * smoke-testing in ssam_request_sync_submit().
	 */
	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_SUSPENDED);

	ssam_controller_unlock(ctrl);
	return 0;
}

/**
 * ssam_controller_resume() - Resume the controller from suspend.
 * @ctrl: The controller to resume.
 *
 * Resume the controller from the suspended state it was put into via
 * ssam_controller_suspend(). This function does not issue display-on and
 * D0-entry notifications. If required, those have to be sent manually after
 * this call.
 *
 * Return: Returns %-EINVAL if the controller is currently not suspended.
 */
int ssam_controller_resume(struct ssam_controller *ctrl)
{
	ssam_controller_lock(ctrl);

	if (ctrl->state != SSAM_CONTROLLER_SUSPENDED) {
		ssam_controller_unlock(ctrl);
		return -EINVAL;
	}

	ssam_dbg(ctrl, "pm: resuming controller\n");

	/*
	 * Set state via write_once even though we're locked, due to
	 * smoke-testing in ssam_request_sync_submit().
	 */
	WRITE_ONCE(ctrl->state, SSAM_CONTROLLER_STARTED);

	ssam_controller_unlock(ctrl);
	return 0;
}


/* -- Top-level request interface ------------------------------------------- */

/**
 * ssam_request_write_data() - Construct and write SAM request message to
 * buffer.
 * @buf:  The buffer to write the data to.
 * @ctrl: The controller via which the request will be sent.
 * @spec: The request data and specification.
 *
 * Constructs a SAM/SSH request message and writes it to the provided buffer.
 * The request and transport counters, specifically RQID and SEQ, will be set
 * in this call. These counters are obtained from the controller. It is thus
 * only valid to send the resulting message via the controller specified here.
 *
 * For calculation of the required buffer size, refer to the
 * SSH_COMMAND_MESSAGE_LENGTH() macro.
 *
 * Return: Returns the number of bytes used in the buffer on success. Returns
 * %-EINVAL if the payload length provided in the request specification is too
 * large (larger than %SSH_COMMAND_MAX_PAYLOAD_SIZE) or if the provided buffer
 * is too small.
 */
ssize_t ssam_request_write_data(struct ssam_span *buf,
				struct ssam_controller *ctrl,
				const struct ssam_request *spec)
{
	struct msgbuf msgb;
	u16 rqid;
	u8 seq;

	if (spec->length > SSH_COMMAND_MAX_PAYLOAD_SIZE)
		return -EINVAL;

	if (SSH_COMMAND_MESSAGE_LENGTH(spec->length) > buf->len)
		return -EINVAL;

	msgb_init(&msgb, buf->ptr, buf->len);
	seq = ssh_seq_next(&ctrl->counter.seq);
	rqid = ssh_rqid_next(&ctrl->counter.rqid);
	msgb_push_cmd(&msgb, seq, rqid, spec);

	return msgb_bytes_used(&msgb);
}
EXPORT_SYMBOL_GPL(ssam_request_write_data);

static void ssam_request_sync_complete(struct ssh_request *rqst,
				       const struct ssh_command *cmd,
				       const struct ssam_span *data, int status)
{
	struct ssh_rtl *rtl = ssh_request_rtl(rqst);
	struct ssam_request_sync *r;

	r = container_of(rqst, struct ssam_request_sync, base);
	r->status = status;

	if (r->resp)
		r->resp->length = 0;

	if (status) {
		rtl_dbg_cond(rtl, "rsp: request failed: %d\n", status);
		return;
	}

	if (!data)	/* Handle requests without a response. */
		return;

	if (!r->resp || !r->resp->pointer) {
		if (data->len)
			rtl_warn(rtl, "rsp: no response buffer provided, dropping data\n");
		return;
	}

	if (data->len > r->resp->capacity) {
		rtl_err(rtl,
			"rsp: response buffer too small, capacity: %zu bytes, got: %zu bytes\n",
			r->resp->capacity, data->len);
		r->status = -ENOSPC;
		return;
	}

	r->resp->length = data->len;
	memcpy(r->resp->pointer, data->ptr, data->len);
}

static void ssam_request_sync_release(struct ssh_request *rqst)
{
	complete_all(&container_of(rqst, struct ssam_request_sync, base)->comp);
}

static const struct ssh_request_ops ssam_request_sync_ops = {
	.release = ssam_request_sync_release,
	.complete = ssam_request_sync_complete,
};

/**
 * ssam_request_sync_alloc() - Allocate a synchronous request.
 * @payload_len: The length of the request payload.
 * @flags:       Flags used for allocation.
 * @rqst:        Where to store the pointer to the allocated request.
 * @buffer:      Where to store the buffer descriptor for the message buffer of
 *               the request.
 *
 * Allocates a synchronous request with corresponding message buffer. The
 * request still needs to be initialized ssam_request_sync_init() before
 * it can be submitted, and the message buffer data must still be set to the
 * returned buffer via ssam_request_sync_set_data() after it has been filled,
 * if need be with adjusted message length.
 *
 * After use, the request and its corresponding message buffer should be freed
 * via ssam_request_sync_free(). The buffer must not be freed separately.
 *
 * Return: Returns zero on success, %-ENOMEM if the request could not be
 * allocated.
 */
int ssam_request_sync_alloc(size_t payload_len, gfp_t flags,
			    struct ssam_request_sync **rqst,
			    struct ssam_span *buffer)
{
	size_t msglen = SSH_COMMAND_MESSAGE_LENGTH(payload_len);

	*rqst = kzalloc(sizeof(**rqst) + msglen, flags);
	if (!*rqst)
		return -ENOMEM;

	buffer->ptr = (u8 *)(*rqst + 1);
	buffer->len = msglen;

	return 0;
}
EXPORT_SYMBOL_GPL(ssam_request_sync_alloc);

/**
 * ssam_request_sync_free() - Free a synchronous request.
 * @rqst: The request to be freed.
 *
 * Free a synchronous request and its corresponding buffer allocated with
 * ssam_request_sync_alloc(). Do not use for requests allocated on the stack
 * or via any other function.
 *
 * Warning: The caller must ensure that the request is not in use any more.
 * I.e. the caller must ensure that it has the only reference to the request
 * and the request is not currently pending. This means that the caller has
 * either never submitted the request, request submission has failed, or the
 * caller has waited until the submitted request has been completed via
 * ssam_request_sync_wait().
 */
void ssam_request_sync_free(struct ssam_request_sync *rqst)
{
	kfree(rqst);
}
EXPORT_SYMBOL_GPL(ssam_request_sync_free);

/**
 * ssam_request_sync_init() - Initialize a synchronous request struct.
 * @rqst:  The request to initialize.
 * @flags: The request flags.
 *
 * Initializes the given request struct. Does not initialize the request
 * message data. This has to be done explicitly after this call via
 * ssam_request_sync_set_data() and the actual message data has to be written
 * via ssam_request_write_data().
 *
 * Return: Returns zero on success or %-EINVAL if the given flags are invalid.
 */
int ssam_request_sync_init(struct ssam_request_sync *rqst,
			   enum ssam_request_flags flags)
{
	int status;

	status = ssh_request_init(&rqst->base, flags, &ssam_request_sync_ops);
	if (status)
		return status;

	init_completion(&rqst->comp);
	rqst->resp = NULL;
	rqst->status = 0;

	return 0;
}
EXPORT_SYMBOL_GPL(ssam_request_sync_init);

/**
 * ssam_request_sync_submit() - Submit a synchronous request.
 * @ctrl: The controller with which to submit the request.
 * @rqst: The request to submit.
 *
 * Submit a synchronous request. The request has to be initialized and
 * properly set up, including response buffer (may be %NULL if no response is
 * expected) and command message data. This function does not wait for the
 * request to be completed.
 *
 * If this function succeeds, ssam_request_sync_wait() must be used to ensure
 * that the request has been completed before the response data can be
 * accessed and/or the request can be freed. On failure, the request may
 * immediately be freed.
 *
 * This function may only be used if the controller is active, i.e. has been
 * initialized and not suspended.
 */
int ssam_request_sync_submit(struct ssam_controller *ctrl,
			     struct ssam_request_sync *rqst)
{
	int status;

	/*
	 * This is only a superficial check. In general, the caller needs to
	 * ensure that the controller is initialized and is not (and does not
	 * get) suspended during use, i.e. until the request has been completed
	 * (if _absolutely_ necessary, by use of ssam_controller_statelock/
	 * ssam_controller_stateunlock, but something like ssam_client_link
	 * should be preferred as this needs to last until the request has been
	 * completed).
	 *
	 * Note that it is actually safe to use this function while the
	 * controller is in the process of being shut down (as ssh_rtl_submit
	 * is safe with regards to this), but it is generally discouraged to do
	 * so.
	 */
	if (WARN_ON(READ_ONCE(ctrl->state) != SSAM_CONTROLLER_STARTED)) {
		ssh_request_put(&rqst->base);
		return -ENODEV;
	}

	status = ssh_rtl_submit(&ctrl->rtl, &rqst->base);
	ssh_request_put(&rqst->base);

	return status;
}
EXPORT_SYMBOL_GPL(ssam_request_sync_submit);

/**
 * ssam_request_sync() - Execute a synchronous request.
 * @ctrl: The controller via which the request will be submitted.
 * @spec: The request specification and payload.
 * @rsp:  The response buffer.
 *
 * Allocates a synchronous request with its message data buffer on the heap
 * via ssam_request_sync_alloc(), fully initializes it via the provided
 * request specification, submits it, and finally waits for its completion
 * before freeing it and returning its status.
 *
 * Return: Returns the status of the request or any failure during setup.
 */
int ssam_request_sync(struct ssam_controller *ctrl,
		      const struct ssam_request *spec,
		      struct ssam_response *rsp)
{
	struct ssam_request_sync *rqst;
	struct ssam_span buf;
	ssize_t len;
	int status;

	status = ssam_request_sync_alloc(spec->length, GFP_KERNEL, &rqst, &buf);
	if (status)
		return status;

	status = ssam_request_sync_init(rqst, spec->flags);
	if (status)
		return status;

	ssam_request_sync_set_resp(rqst, rsp);

	len = ssam_request_write_data(&buf, ctrl, spec);
	if (len < 0) {
		ssam_request_sync_free(rqst);
		return len;
	}

	ssam_request_sync_set_data(rqst, buf.ptr, len);

	status = ssam_request_sync_submit(ctrl, rqst);
	if (!status)
		status = ssam_request_sync_wait(rqst);

	ssam_request_sync_free(rqst);
	return status;
}
EXPORT_SYMBOL_GPL(ssam_request_sync);

/**
 * ssam_request_sync_with_buffer() - Execute a synchronous request with the
 * provided buffer as back-end for the message buffer.
 * @ctrl: The controller via which the request will be submitted.
 * @spec: The request specification and payload.
 * @rsp:  The response buffer.
 * @buf:  The buffer for the request message data.
 *
 * Allocates a synchronous request struct on the stack, fully initializes it
 * using the provided buffer as message data buffer, submits it, and then
 * waits for its completion before returning its status. The
 * SSH_COMMAND_MESSAGE_LENGTH() macro can be used to compute the required
 * message buffer size.
 *
 * This function does essentially the same as ssam_request_sync(), but instead
 * of dynamically allocating the request and message data buffer, it uses the
 * provided message data buffer and stores the (small) request struct on the
 * heap.
 *
 * Return: Returns the status of the request or any failure during setup.
 */
int ssam_request_sync_with_buffer(struct ssam_controller *ctrl,
				  const struct ssam_request *spec,
				  struct ssam_response *rsp,
				  struct ssam_span *buf)
{
	struct ssam_request_sync rqst;
	ssize_t len;
	int status;

	status = ssam_request_sync_init(&rqst, spec->flags);
	if (status)
		return status;

	ssam_request_sync_set_resp(&rqst, rsp);

	len = ssam_request_write_data(buf, ctrl, spec);
	if (len < 0)
		return len;

	ssam_request_sync_set_data(&rqst, buf->ptr, len);

	status = ssam_request_sync_submit(ctrl, &rqst);
	if (!status)
		status = ssam_request_sync_wait(&rqst);

	return status;
}
EXPORT_SYMBOL_GPL(ssam_request_sync_with_buffer);


/* -- Internal SAM requests. ------------------------------------------------ */

SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_get_firmware_version, __le32, {
	.target_category = SSAM_SSH_TC_SAM,
	.target_id       = 0x01,
	.command_id      = 0x13,
	.instance_id     = 0x00,
});

SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_display_off, u8, {
	.target_category = SSAM_SSH_TC_SAM,
	.target_id       = 0x01,
	.command_id      = 0x15,
	.instance_id     = 0x00,
});

SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_display_on, u8, {
	.target_category = SSAM_SSH_TC_SAM,
	.target_id       = 0x01,
	.command_id      = 0x16,
	.instance_id     = 0x00,
});

SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_d0_exit, u8, {
	.target_category = SSAM_SSH_TC_SAM,
	.target_id       = 0x01,
	.command_id      = 0x33,
	.instance_id     = 0x00,
});

SSAM_DEFINE_SYNC_REQUEST_R(ssam_ssh_notif_d0_entry, u8, {
	.target_category = SSAM_SSH_TC_SAM,
	.target_id       = 0x01,
	.command_id      = 0x34,
	.instance_id     = 0x00,
});

/**
 * struct ssh_notification_params - Command payload to enable/disable SSH
 * notifications.
 * @target_category: The target category for which notifications should be
 *                   enabled/disabled.
 * @flags:           Flags determining how notifications are being sent.
 * @request_id:      The request ID that is used to send these notifications.
 * @instance_id:     The specific instance in the given target category for
 *                   which notifications should be enabled.
 */
struct ssh_notification_params {
	u8 target_category;
	u8 flags;
	__le16 request_id;
	u8 instance_id;
} __packed;

static_assert(sizeof(struct ssh_notification_params) == 5);

static int __ssam_ssh_event_request(struct ssam_controller *ctrl,
				    struct ssam_event_registry reg, u8 cid,
				    struct ssam_event_id id, u8 flags)
{
	struct ssh_notification_params params;
	struct ssam_request rqst;
	struct ssam_response result;
	int status;

	u16 rqid = ssh_tc_to_rqid(id.target_category);
	u8 buf = 0;

	/* Only allow RQIDs that lie within the event spectrum. */
	if (!ssh_rqid_is_event(rqid))
		return -EINVAL;

	params.target_category = id.target_category;
	params.instance_id = id.instance;
	params.flags = flags;
	put_unaligned_le16(rqid, &params.request_id);

	rqst.target_category = reg.target_category;
	rqst.target_id = reg.target_id;
	rqst.command_id = cid;
	rqst.instance_id = 0x00;
	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
	rqst.length = sizeof(params);
	rqst.payload = (u8 *)&params;

	result.capacity = sizeof(buf);
	result.length = 0;
	result.pointer = &buf;

	status = ssam_retry(ssam_request_sync_onstack, ctrl, &rqst, &result,
			    sizeof(params));

	return status < 0 ? status : buf;
}

/**
 * ssam_ssh_event_enable() - Enable SSH event.
 * @ctrl:  The controller for which to enable the event.
 * @reg:   The event registry describing what request to use for enabling and
 *         disabling the event.
 * @id:    The event identifier.
 * @flags: The event flags.
 *
 * Enables the specified event on the EC. This function does not manage
 * reference counting of enabled events and is basically only a wrapper for
 * the raw EC request. If the specified event is already enabled, the EC will
 * ignore this request.
 *
 * Return: Returns the status of the executed SAM request (zero on success and
 * negative on direct failure) or %-EPROTO if the request response indicates a
 * failure.
 */
static int ssam_ssh_event_enable(struct ssam_controller *ctrl,
				 struct ssam_event_registry reg,
				 struct ssam_event_id id, u8 flags)
{
	int status;

	status = __ssam_ssh_event_request(ctrl, reg, reg.cid_enable, id, flags);

	if (status < 0 && status != -EINVAL) {
		ssam_err(ctrl,
			 "failed to enable event source (tc: %#04x, iid: %#04x, reg: %#04x)\n",
			 id.target_category, id.instance, reg.target_category);
	}

	if (status > 0) {
		ssam_err(ctrl,
			 "unexpected result while enabling event source: %#04x (tc: %#04x, iid: %#04x, reg: %#04x)\n",
			 status, id.target_category, id.instance, reg.target_category);
		return -EPROTO;
	}

	return status;
}

/**
 * ssam_ssh_event_disable() - Disable SSH event.
 * @ctrl:  The controller for which to disable the event.
 * @reg:   The event registry describing what request to use for enabling and
 *         disabling the event (must be same as used when enabling the event).
 * @id:    The event identifier.
 * @flags: The event flags (likely ignored for disabling of events).
 *
 * Disables the specified event on the EC. This function does not manage
 * reference counting of enabled events and is basically only a wrapper for
 * the raw EC request. If the specified event is already disabled, the EC will
 * ignore this request.
 *
 * Return: Returns the status of the executed SAM request (zero on success and
 * negative on direct failure) or %-EPROTO if the request response indicates a
 * failure.
 */
static int ssam_ssh_event_disable(struct ssam_controller *ctrl,
				  struct ssam_event_registry reg,
				  struct ssam_event_id id, u8 flags)
{
	int status;

	status = __ssam_ssh_event_request(ctrl, reg, reg.cid_enable, id, flags);

	if (status < 0 && status != -EINVAL) {
		ssam_err(ctrl,
			 "failed to disable event source (tc: %#04x, iid: %#04x, reg: %#04x)\n",
			 id.target_category, id.instance, reg.target_category);
	}

	if (status > 0) {
		ssam_err(ctrl,
			 "unexpected result while disabling event source: %#04x (tc: %#04x, iid: %#04x, reg: %#04x)\n",
			 status, id.target_category, id.instance, reg.target_category);
		return -EPROTO;
	}

	return status;
}


/* -- Wrappers for internal SAM requests. ----------------------------------- */

/**
 * ssam_get_firmware_version() - Get the SAM/EC firmware version.
 * @ctrl:    The controller.
 * @version: Where to store the version number.
 *
 * Return: Returns zero on success or the status of the executed SAM request
 * if that request failed.
 */
int ssam_get_firmware_version(struct ssam_controller *ctrl, u32 *version)
{
	__le32 __version;
	int status;

	status = ssam_retry(ssam_ssh_get_firmware_version, ctrl, &__version);
	if (status)
		return status;

	*version = le32_to_cpu(__version);
	return 0;
}

/**
 * ssam_ctrl_notif_display_off() - Notify EC that the display has been turned
 * off.
 * @ctrl: The controller.
 *
 * Notify the EC that the display has been turned off and the driver may enter
 * a lower-power state. This will prevent events from being sent directly.
 * Rather, the EC signals an event by pulling the wakeup GPIO high for as long
 * as there are pending events. The events then need to be manually released,
 * one by one, via the GPIO callback request. All pending events accumulated
 * during this state can also be released by issuing the display-on
 * notification, e.g. via ssam_ctrl_notif_display_on(), which will also reset
 * the GPIO.
 *
 * On some devices, specifically ones with an integrated keyboard, the keyboard
 * backlight will be turned off by this call.
 *
 * This function will only send the display-off notification command if
 * display notifications are supported by the EC. Currently all known devices
 * support these notifications.
 *
 * Use ssam_ctrl_notif_display_on() to reverse the effects of this function.
 *
 * Return: Returns zero on success or if no request has been executed, the
 * status of the executed SAM request if that request failed, or %-EPROTO if
 * an unexpected response has been received.
 */
int ssam_ctrl_notif_display_off(struct ssam_controller *ctrl)
{
	int status;
	u8 response;

	ssam_dbg(ctrl, "pm: notifying display off\n");

	status = ssam_retry(ssam_ssh_notif_display_off, ctrl, &response);
	if (status)
		return status;

	if (response != 0) {
		ssam_err(ctrl, "unexpected response from display-off notification: %#04x\n",
			 response);
		return -EPROTO;
	}

	return 0;
}

/**
 * ssam_ctrl_notif_display_on() - Notify EC that the display has been turned on.
 * @ctrl: The controller.
 *
 * Notify the EC that the display has been turned back on and the driver has
 * exited its lower-power state. This notification is the counterpart to the
 * display-off notification sent via ssam_ctrl_notif_display_off() and will
 * reverse its effects, including resetting events to their default behavior.
 *
 * This function will only send the display-on notification command if display
 * notifications are supported by the EC. Currently all known devices support
 * these notifications.
 *
 * See ssam_ctrl_notif_display_off() for more details.
 *
 * Return: Returns zero on success or if no request has been executed, the
 * status of the executed SAM request if that request failed, or %-EPROTO if
 * an unexpected response has been received.
 */
int ssam_ctrl_notif_display_on(struct ssam_controller *ctrl)
{
	int status;
	u8 response;

	ssam_dbg(ctrl, "pm: notifying display on\n");

	status = ssam_retry(ssam_ssh_notif_display_on, ctrl, &response);
	if (status)
		return status;

	if (response != 0) {
		ssam_err(ctrl, "unexpected response from display-on notification: %#04x\n",
			 response);
		return -EPROTO;
	}

	return 0;
}

/**
 * ssam_ctrl_notif_d0_exit() - Notify EC that the driver/device exits the D0
 * power state.
 * @ctrl: The controller
 *
 * Notifies the EC that the driver prepares to exit the D0 power state in
 * favor of a lower-power state. Exact effects of this function related to the
 * EC are currently unknown.
 *
 * This function will only send the D0-exit notification command if D0-state
 * notifications are supported by the EC. Only newer Surface generations
 * support these notifications.
 *
 * Use ssam_ctrl_notif_d0_entry() to reverse the effects of this function.
 *
 * Return: Returns zero on success or if no request has been executed, the
 * status of the executed SAM request if that request failed, or %-EPROTO if
 * an unexpected response has been received.
 */
int ssam_ctrl_notif_d0_exit(struct ssam_controller *ctrl)
{
	int status;
	u8 response;

	if (!ctrl->caps.d3_closes_handle)
		return 0;

	ssam_dbg(ctrl, "pm: notifying D0 exit\n");

	status = ssam_retry(ssam_ssh_notif_d0_exit, ctrl, &response);
	if (status)
		return status;

	if (response != 0) {
		ssam_err(ctrl, "unexpected response from D0-exit notification: %#04x\n",
			 response);
		return -EPROTO;
	}

	return 0;
}

/**
 * ssam_ctrl_notif_d0_entry() - Notify EC that the driver/device enters the D0
 * power state.
 * @ctrl: The controller
 *
 * Notifies the EC that the driver has exited a lower-power state and entered
 * the D0 power state. Exact effects of this function related to the EC are
 * currently unknown.
 *
 * This function will only send the D0-entry notification command if D0-state
 * notifications are supported by the EC. Only newer Surface generations
 * support these notifications.
 *
 * See ssam_ctrl_notif_d0_exit() for more details.
 *
 * Return: Returns zero on success or if no request has been executed, the
 * status of the executed SAM request if that request failed, or %-EPROTO if
 * an unexpected response has been received.
 */
int ssam_ctrl_notif_d0_entry(struct ssam_controller *ctrl)
{
	int status;
	u8 response;

	if (!ctrl->caps.d3_closes_handle)
		return 0;

	ssam_dbg(ctrl, "pm: notifying D0 entry\n");

	status = ssam_retry(ssam_ssh_notif_d0_entry, ctrl, &response);
	if (status)
		return status;

	if (response != 0) {
		ssam_err(ctrl, "unexpected response from D0-entry notification: %#04x\n",
			 response);
		return -EPROTO;
	}

	return 0;
}


/* -- Top-level event registry interface. ----------------------------------- */

/**
 * ssam_notifier_register() - Register an event notifier.
 * @ctrl: The controller to register the notifier on.
 * @n:    The event notifier to register.
 *
 * Register an event notifier and increment the usage counter of the
 * associated SAM event. If the event was previously not enabled, it will be
 * enabled during this call.
 *
 * Return: Returns zero on success, %-ENOSPC if there have already been
 * %INT_MAX notifiers for the event ID/type associated with the notifier block
 * registered, %-ENOMEM if the corresponding event entry could not be
 * allocated. If this is the first time that a notifier block is registered
 * for the specific associated event, returns the status of the event-enable
 * EC-command.
 */
int ssam_notifier_register(struct ssam_controller *ctrl,
			   struct ssam_event_notifier *n)
{
	u16 rqid = ssh_tc_to_rqid(n->event.id.target_category);
	struct ssam_nf_refcount_entry *entry;
	struct ssam_nf_head *nf_head;
	struct ssam_nf *nf;
	int status;

	if (!ssh_rqid_is_event(rqid))
		return -EINVAL;

	nf = &ctrl->cplt.event.notif;
	nf_head = &nf->head[ssh_rqid_to_event(rqid)];

	mutex_lock(&nf->lock);

	entry = ssam_nf_refcount_inc(nf, n->event.reg, n->event.id);
	if (IS_ERR(entry)) {
		mutex_unlock(&nf->lock);
		return PTR_ERR(entry);
	}

	ssam_dbg(ctrl, "enabling event (reg: %#04x, tc: %#04x, iid: %#04x, rc: %d)\n",
		 n->event.reg.target_category, n->event.id.target_category,
		 n->event.id.instance, entry->refcount);

	status = ssam_nfblk_insert(nf_head, &n->base);
	if (status) {
		entry = ssam_nf_refcount_dec(nf, n->event.reg, n->event.id);
		if (entry->refcount == 0)
			kfree(entry);

		mutex_unlock(&nf->lock);
		return status;
	}

	if (entry->refcount == 1) {
		status = ssam_ssh_event_enable(ctrl, n->event.reg, n->event.id,
					       n->event.flags);
		if (status) {
			ssam_nfblk_remove(&n->base);
			kfree(ssam_nf_refcount_dec(nf, n->event.reg, n->event.id));
			mutex_unlock(&nf->lock);
			synchronize_srcu(&nf_head->srcu);
			return status;
		}

		entry->flags = n->event.flags;

	} else if (entry->flags != n->event.flags) {
		ssam_warn(ctrl,
			  "inconsistent flags when enabling event: got %#04x, expected %#04x (reg: %#04x, tc: %#04x, iid: %#04x)\n",
			  n->event.flags, entry->flags, n->event.reg.target_category,
			  n->event.id.target_category, n->event.id.instance);
	}

	mutex_unlock(&nf->lock);
	return 0;
}
EXPORT_SYMBOL_GPL(ssam_notifier_register);

/**
 * ssam_notifier_unregister() - Unregister an event notifier.
 * @ctrl: The controller the notifier has been registered on.
 * @n:    The event notifier to unregister.
 *
 * Unregister an event notifier and decrement the usage counter of the
 * associated SAM event. If the usage counter reaches zero, the event will be
 * disabled.
 *
 * Return: Returns zero on success, %-ENOENT if the given notifier block has
 * not been registered on the controller. If the given notifier block was the
 * last one associated with its specific event, returns the status of the
 * event-disable EC-command.
 */
int ssam_notifier_unregister(struct ssam_controller *ctrl,
			     struct ssam_event_notifier *n)
{
	u16 rqid = ssh_tc_to_rqid(n->event.id.target_category);
	struct ssam_nf_refcount_entry *entry;
	struct ssam_nf_head *nf_head;
	struct ssam_nf *nf;
	int status = 0;

	if (!ssh_rqid_is_event(rqid))
		return -EINVAL;

	nf = &ctrl->cplt.event.notif;
	nf_head = &nf->head[ssh_rqid_to_event(rqid)];

	mutex_lock(&nf->lock);

	if (!ssam_nfblk_find(nf_head, &n->base)) {
		mutex_unlock(&nf->lock);
		return -ENOENT;
	}

	entry = ssam_nf_refcount_dec(nf, n->event.reg, n->event.id);
	if (WARN_ON(!entry)) {
		/*
		 * If this does not return an entry, there's a logic error
		 * somewhere: The notifier block is registered, but the event
		 * refcount entry is not there. Remove the notifier block
		 * anyways.
		 */
		status = -ENOENT;
		goto remove;
	}

	ssam_dbg(ctrl, "disabling event (reg: %#04x, tc: %#04x, iid: %#04x, rc: %d)\n",
		 n->event.reg.target_category, n->event.id.target_category,
		 n->event.id.instance, entry->refcount);

	if (entry->flags != n->event.flags) {
		ssam_warn(ctrl,
			  "inconsistent flags when disabling event: got %#04x, expected %#04x (reg: %#04x, tc: %#04x, iid: %#04x)\n",
			  n->event.flags, entry->flags, n->event.reg.target_category,
			  n->event.id.target_category, n->event.id.instance);
	}

	if (entry->refcount == 0) {
		status = ssam_ssh_event_disable(ctrl, n->event.reg, n->event.id,
						n->event.flags);
		kfree(entry);
	}

remove:
	ssam_nfblk_remove(&n->base);
	mutex_unlock(&nf->lock);
	synchronize_srcu(&nf_head->srcu);

	return status;
}
EXPORT_SYMBOL_GPL(ssam_notifier_unregister);

/**
 * ssam_notifier_disable_registered() - Disable events for all registered
 * notifiers.
 * @ctrl: The controller for which to disable the notifiers/events.
 *
 * Disables events for all currently registered notifiers. In case of an error
 * (EC command failing), all previously disabled events will be restored and
 * the error code returned.
 *
 * This function is intended to disable all events prior to hibernation entry.
 * See ssam_notifier_restore_registered() to restore/re-enable all events
 * disabled with this function.
 *
 * Note that this function will not disable events for notifiers registered
 * after calling this function. It should thus be made sure that no new
 * notifiers are going to be added after this call and before the corresponding
 * call to ssam_notifier_restore_registered().
 *
 * Return: Returns zero on success. In case of failure returns the error code
 * returned by the failed EC command to disable an event.
 */
int ssam_notifier_disable_registered(struct ssam_controller *ctrl)
{
	struct ssam_nf *nf = &ctrl->cplt.event.notif;
	struct rb_node *n;
	int status;

	mutex_lock(&nf->lock);
	for (n = rb_first(&nf->refcount); n; n = rb_next(n)) {
		struct ssam_nf_refcount_entry *e;

		e = rb_entry(n, struct ssam_nf_refcount_entry, node);
		status = ssam_ssh_event_disable(ctrl, e->key.reg,
						e->key.id, e->flags);
		if (status)
			goto err;
	}
	mutex_unlock(&nf->lock);

	return 0;

err:
	for (n = rb_prev(n); n; n = rb_prev(n)) {
		struct ssam_nf_refcount_entry *e;

		e = rb_entry(n, struct ssam_nf_refcount_entry, node);
		ssam_ssh_event_enable(ctrl, e->key.reg, e->key.id, e->flags);
	}
	mutex_unlock(&nf->lock);

	return status;
}

/**
 * ssam_notifier_restore_registered() - Restore/re-enable events for all
 * registered notifiers.
 * @ctrl: The controller for which to restore the notifiers/events.
 *
 * Restores/re-enables all events for which notifiers have been registered on
 * the given controller. In case of a failure, the error is logged and the
 * function continues to try and enable the remaining events.
 *
 * This function is intended to restore/re-enable all registered events after
 * hibernation. See ssam_notifier_disable_registered() for the counter part
 * disabling the events and more details.
 */
void ssam_notifier_restore_registered(struct ssam_controller *ctrl)
{
	struct ssam_nf *nf = &ctrl->cplt.event.notif;
	struct rb_node *n;

	mutex_lock(&nf->lock);
	for (n = rb_first(&nf->refcount); n; n = rb_next(n)) {
		struct ssam_nf_refcount_entry *e;

		e = rb_entry(n, struct ssam_nf_refcount_entry, node);

		/* Ignore errors, will get logged in call. */
		ssam_ssh_event_enable(ctrl, e->key.reg, e->key.id, e->flags);
	}
	mutex_unlock(&nf->lock);
}

/**
 * ssam_notifier_is_empty() - Check if there are any registered notifiers.
 * @ctrl: The controller to check on.
 *
 * Return: Returns %true if there are currently no notifiers registered on the
 * controller, %false otherwise.
 */
static bool ssam_notifier_is_empty(struct ssam_controller *ctrl)
{
	struct ssam_nf *nf = &ctrl->cplt.event.notif;
	bool result;

	mutex_lock(&nf->lock);
	result = ssam_nf_refcount_empty(nf);
	mutex_unlock(&nf->lock);

	return result;
}

/**
 * ssam_notifier_unregister_all() - Unregister all currently registered
 * notifiers.
 * @ctrl: The controller to unregister the notifiers on.
 *
 * Unregisters all currently registered notifiers. This function is used to
 * ensure that all notifiers will be unregistered and associated
 * entries/resources freed when the controller is being shut down.
 */
static void ssam_notifier_unregister_all(struct ssam_controller *ctrl)
{
	struct ssam_nf *nf = &ctrl->cplt.event.notif;
	struct ssam_nf_refcount_entry *e, *n;

	mutex_lock(&nf->lock);
	rbtree_postorder_for_each_entry_safe(e, n, &nf->refcount, node) {
		/* Ignore errors, will get logged in call. */
		ssam_ssh_event_disable(ctrl, e->key.reg, e->key.id, e->flags);
		kfree(e);
	}
	nf->refcount = RB_ROOT;
	mutex_unlock(&nf->lock);
}


/* -- Wakeup IRQ. ----------------------------------------------------------- */

static irqreturn_t ssam_irq_handle(int irq, void *dev_id)
{
	struct ssam_controller *ctrl = dev_id;

	ssam_dbg(ctrl, "pm: wake irq triggered\n");

	/*
	 * Note: Proper wakeup detection is currently unimplemented.
	 *       When the EC is in display-off or any other non-D0 state, it
	 *       does not send events/notifications to the host. Instead it
	 *       signals that there are events available via the wakeup IRQ.
	 *       This driver is responsible for calling back to the EC to
	 *       release these events one-by-one.
	 *
	 *       This IRQ should not cause a full system resume by its own.
	 *       Instead, events should be handled by their respective subsystem
	 *       drivers, which in turn should signal whether a full system
	 *       resume should be performed.
	 *
	 * TODO: Send GPIO callback command repeatedly to EC until callback
	 *       returns 0x00. Return flag of callback is "has more events".
	 *       Each time the command is sent, one event is "released". Once
	 *       all events have been released (return = 0x00), the GPIO is
	 *       re-armed. Detect wakeup events during this process, go back to
	 *       sleep if no wakeup event has been received.
	 */

	return IRQ_HANDLED;
}

/**
 * ssam_irq_setup() - Set up SAM EC wakeup-GPIO interrupt.
 * @ctrl: The controller for which the IRQ should be set up.
 *
 * Set up an IRQ for the wakeup-GPIO pin of the SAM EC. This IRQ can be used
 * to wake the device from a low power state.
 *
 * Note that this IRQ can only be triggered while the EC is in the display-off
 * state. In this state, events are not sent to the host in the usual way.
 * Instead the wakeup-GPIO gets pulled to "high" as long as there are pending
 * events and these events need to be released one-by-one via the GPIO
 * callback request, either until there are no events left and the GPIO is
 * reset, or all at once by transitioning the EC out of the display-off state,
 * which will also clear the GPIO.
 *
 * Not all events, however, should trigger a full system wakeup. Instead the
 * driver should, if necessary, inspect and forward each event to the
 * corresponding subsystem, which in turn should decide if the system needs to
 * be woken up. This logic has not been implemented yet, thus wakeup by this
 * IRQ should be disabled by default to avoid spurious wake-ups, caused, for
 * example, by the remaining battery percentage changing. Refer to comments in
 * this function and comments in the corresponding IRQ handler for more
 * details on how this should be implemented.
 *
 * See also ssam_ctrl_notif_display_off() and ssam_ctrl_notif_display_off()
 * for functions to transition the EC into and out of the display-off state as
 * well as more details on it.
 *
 * The IRQ is disabled by default and has to be enabled before it can wake up
 * the device from suspend via ssam_irq_arm_for_wakeup(). On teardown, the IRQ
 * should be freed via ssam_irq_free().
 */
int ssam_irq_setup(struct ssam_controller *ctrl)
{
	struct device *dev = ssam_controller_device(ctrl);
	struct gpio_desc *gpiod;
	int irq;
	int status;

	/*
	 * The actual GPIO interrupt is declared in ACPI as TRIGGER_HIGH.
	 * However, the GPIO line only gets reset by sending the GPIO callback
	 * command to SAM (or alternatively the display-on notification). As
	 * proper handling for this interrupt is not implemented yet, leaving
	 * the IRQ at TRIGGER_HIGH would cause an IRQ storm (as the callback
	 * never gets sent and thus the line never gets reset). To avoid this,
	 * mark the IRQ as TRIGGER_RISING for now, only creating a single
	 * interrupt, and let the SAM resume callback during the controller
	 * resume process clear it.
	 */
	const int irqf = IRQF_SHARED | IRQF_ONESHOT |
			 IRQF_TRIGGER_RISING | IRQF_NO_AUTOEN;

	gpiod = gpiod_get(dev, "ssam_wakeup-int", GPIOD_ASIS);
	if (IS_ERR(gpiod))
		return PTR_ERR(gpiod);

	irq = gpiod_to_irq(gpiod);
	gpiod_put(gpiod);

	if (irq < 0)
		return irq;

	status = request_threaded_irq(irq, NULL, ssam_irq_handle, irqf,
				      "ssam_wakeup", ctrl);
	if (status)
		return status;

	ctrl->irq.num = irq;
	return 0;
}

/**
 * ssam_irq_free() - Free SAM EC wakeup-GPIO interrupt.
 * @ctrl: The controller for which the IRQ should be freed.
 *
 * Free the wakeup-GPIO IRQ previously set-up via ssam_irq_setup().
 */
void ssam_irq_free(struct ssam_controller *ctrl)
{
	free_irq(ctrl->irq.num, ctrl);
	ctrl->irq.num = -1;
}

/**
 * ssam_irq_arm_for_wakeup() - Arm the EC IRQ for wakeup, if enabled.
 * @ctrl: The controller for which the IRQ should be armed.
 *
 * Sets up the IRQ so that it can be used to wake the device. Specifically,
 * this function enables the irq and then, if the device is allowed to wake up
 * the system, calls enable_irq_wake(). See ssam_irq_disarm_wakeup() for the
 * corresponding function to disable the IRQ.
 *
 * This function is intended to arm the IRQ before entering S2idle suspend.
 *
 * Note: calls to ssam_irq_arm_for_wakeup() and ssam_irq_disarm_wakeup() must
 * be balanced.
 */
int ssam_irq_arm_for_wakeup(struct ssam_controller *ctrl)
{
	struct device *dev = ssam_controller_device(ctrl);
	int status;

	enable_irq(ctrl->irq.num);
	if (device_may_wakeup(dev)) {
		status = enable_irq_wake(ctrl->irq.num);
		if (status) {
			ssam_err(ctrl, "failed to enable wake IRQ: %d\n", status);
			disable_irq(ctrl->irq.num);
			return status;
		}

		ctrl->irq.wakeup_enabled = true;
	} else {
		ctrl->irq.wakeup_enabled = false;
	}

	return 0;
}

/**
 * ssam_irq_disarm_wakeup() - Disarm the wakeup IRQ.
 * @ctrl: The controller for which the IRQ should be disarmed.
 *
 * Disarm the IRQ previously set up for wake via ssam_irq_arm_for_wakeup().
 *
 * This function is intended to disarm the IRQ after exiting S2idle suspend.
 *
 * Note: calls to ssam_irq_arm_for_wakeup() and ssam_irq_disarm_wakeup() must
 * be balanced.
 */
void ssam_irq_disarm_wakeup(struct ssam_controller *ctrl)
{
	int status;

	if (ctrl->irq.wakeup_enabled) {
		status = disable_irq_wake(ctrl->irq.num);
		if (status)
			ssam_err(ctrl, "failed to disable wake IRQ: %d\n", status);

		ctrl->irq.wakeup_enabled = false;
	}
	disable_irq(ctrl->irq.num);
}