summaryrefslogtreecommitdiffstats
path: root/drivers/net/wan/dscc4.c
blob: 34cff6ce6d27fd09ac6833972041650f6d15cee6 (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
/*
 * drivers/net/wan/dscc4/dscc4.c: a DSCC4 HDLC driver for Linux
 *
 * This software may be used and distributed according to the terms of the
 * GNU General Public License.
 *
 * The author may be reached as romieu@cogenit.fr.
 * Specific bug reports/asian food will be welcome.
 *
 * Special thanks to the nice people at CS-Telecom for the hardware and the
 * access to the test/measure tools.
 *
 *
 *                             Theory of Operation
 *
 * I. Board Compatibility
 *
 * This device driver is designed for the Siemens PEB20534 4 ports serial
 * controller as found on Etinc PCISYNC cards. The documentation for the
 * chipset is available at http://www.infineon.com:
 * - Data Sheet "DSCC4, DMA Supported Serial Communication Controller with
 * 4 Channels, PEB 20534 Version 2.1, PEF 20534 Version 2.1";
 * - Application Hint "Management of DSCC4 on-chip FIFO resources".
 * - Errata sheet DS5 (courtesy of Michael Skerritt).
 * Jens David has built an adapter based on the same chipset. Take a look
 * at http://www.afthd.tu-darmstadt.de/~dg1kjd/pciscc4 for a specific
 * driver.
 * Sample code (2 revisions) is available at Infineon.
 *
 * II. Board-specific settings
 *
 * Pcisync can transmit some clock signal to the outside world on the
 * *first two* ports provided you put a quartz and a line driver on it and
 * remove the jumpers. The operation is described on Etinc web site. If you
 * go DCE on these ports, don't forget to use an adequate cable.
 *
 * Sharing of the PCI interrupt line for this board is possible.
 *
 * III. Driver operation
 *
 * The rx/tx operations are based on a linked list of descriptors. The driver
 * doesn't use HOLD mode any more. HOLD mode is definitely buggy and the more
 * I tried to fix it, the more it started to look like (convoluted) software
 * mutation of LxDA method. Errata sheet DS5 suggests to use LxDA: consider
 * this a rfc2119 MUST.
 *
 * Tx direction
 * When the tx ring is full, the xmit routine issues a call to netdev_stop.
 * The device is supposed to be enabled again during an ALLS irq (we could
 * use HI but as it's easy to lose events, it's fscked).
 *
 * Rx direction
 * The received frames aren't supposed to span over multiple receiving areas.
 * I may implement it some day but it isn't the highest ranked item.
 *
 * IV. Notes
 * The current error (XDU, RFO) recovery code is untested.
 * So far, RDO takes his RX channel down and the right sequence to enable it
 * again is still a mistery. If RDO happens, plan a reboot. More details
 * in the code (NB: as this happens, TX still works).
 * Don't mess the cables during operation, especially on DTE ports. I don't
 * suggest it for DCE either but at least one can get some messages instead
 * of a complete instant freeze.
 * Tests are done on Rev. 20 of the silicium. The RDO handling changes with
 * the documentation/chipset releases.
 *
 * TODO:
 * - test X25.
 * - use polling at high irq/s,
 * - performance analysis,
 * - endianness.
 *
 * 2001/12/10	Daniela Squassoni  <daniela@cyclades.com>
 * - Contribution to support the new generic HDLC layer.
 *
 * 2002/01	Ueimor
 * - old style interface removal
 * - dscc4_release_ring fix (related to DMA mapping)
 * - hard_start_xmit fix (hint: TxSizeMax)
 * - misc crapectomy.
 */

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/list.h>
#include <linux/ioport.h>
#include <linux/pci.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/slab.h>

#include <asm/system.h>
#include <asm/cache.h>
#include <asm/byteorder.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/irq.h>

#include <linux/init.h>
#include <linux/string.h>

#include <linux/if_arp.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/delay.h>
#include <linux/hdlc.h>
#include <linux/mutex.h>

/* Version */
static const char version[] = "$Id: dscc4.c,v 1.173 2003/09/20 23:55:34 romieu Exp $ for Linux\n";
static int debug;
static int quartz;

#ifdef CONFIG_DSCC4_PCI_RST
static DEFINE_MUTEX(dscc4_mutex);
static u32 dscc4_pci_config_store[16];
#endif

#define	DRV_NAME	"dscc4"

#undef DSCC4_POLLING

/* Module parameters */

MODULE_AUTHOR("Maintainer: Francois Romieu <romieu@cogenit.fr>");
MODULE_DESCRIPTION("Siemens PEB20534 PCI Controler");
MODULE_LICENSE("GPL");
module_param(debug, int, 0);
MODULE_PARM_DESC(debug,"Enable/disable extra messages");
module_param(quartz, int, 0);
MODULE_PARM_DESC(quartz,"If present, on-board quartz frequency (Hz)");

/* Structures */

struct thingie {
	int define;
	u32 bits;
};

struct TxFD {
	__le32 state;
	__le32 next;
	__le32 data;
	__le32 complete;
	u32 jiffies; /* Allows sizeof(TxFD) == sizeof(RxFD) + extra hack */
		     /* FWIW, datasheet calls that "dummy" and says that card
		      * never looks at it; neither does the driver */
};

struct RxFD {
	__le32 state1;
	__le32 next;
	__le32 data;
	__le32 state2;
	__le32 end;
};

#define DUMMY_SKB_SIZE		64
#define TX_LOW			8
#define TX_RING_SIZE		32
#define RX_RING_SIZE		32
#define TX_TOTAL_SIZE		TX_RING_SIZE*sizeof(struct TxFD)
#define RX_TOTAL_SIZE		RX_RING_SIZE*sizeof(struct RxFD)
#define IRQ_RING_SIZE		64		/* Keep it a multiple of 32 */
#define TX_TIMEOUT		(HZ/10)
#define DSCC4_HZ_MAX		33000000
#define BRR_DIVIDER_MAX		64*0x00004000	/* Cf errata DS5 p.10 */
#define dev_per_card		4
#define SCC_REGISTERS_MAX	23		/* Cf errata DS5 p.4 */

#define SOURCE_ID(flags)	(((flags) >> 28) & 0x03)
#define TO_SIZE(state)		(((state) >> 16) & 0x1fff)

/*
 * Given the operating range of Linux HDLC, the 2 defines below could be
 * made simpler. However they are a fine reminder for the limitations of
 * the driver: it's better to stay < TxSizeMax and < RxSizeMax.
 */
#define TO_STATE_TX(len)	cpu_to_le32(((len) & TxSizeMax) << 16)
#define TO_STATE_RX(len)	cpu_to_le32((RX_MAX(len) % RxSizeMax) << 16)
#define RX_MAX(len)		((((len) >> 5) + 1) << 5)	/* Cf RLCR */
#define SCC_REG_START(dpriv)	(SCC_START+(dpriv->dev_id)*SCC_OFFSET)

struct dscc4_pci_priv {
        __le32 *iqcfg;
        int cfg_cur;
        spinlock_t lock;
        struct pci_dev *pdev;

        struct dscc4_dev_priv *root;
        dma_addr_t iqcfg_dma;
	u32 xtal_hz;
};

struct dscc4_dev_priv {
        struct sk_buff *rx_skbuff[RX_RING_SIZE];
        struct sk_buff *tx_skbuff[TX_RING_SIZE];

        struct RxFD *rx_fd;
        struct TxFD *tx_fd;
        __le32 *iqrx;
        __le32 *iqtx;

	/* FIXME: check all the volatile are required */
        volatile u32 tx_current;
        u32 rx_current;
        u32 iqtx_current;
        u32 iqrx_current;

        volatile u32 tx_dirty;
        volatile u32 ltda;
        u32 rx_dirty;
        u32 lrda;

        dma_addr_t tx_fd_dma;
        dma_addr_t rx_fd_dma;
        dma_addr_t iqtx_dma;
        dma_addr_t iqrx_dma;

	u32 scc_regs[SCC_REGISTERS_MAX]; /* Cf errata DS5 p.4 */

	struct timer_list timer;

        struct dscc4_pci_priv *pci_priv;
        spinlock_t lock;

        int dev_id;
	volatile u32 flags;
	u32 timer_help;

	unsigned short encoding;
	unsigned short parity;
	struct net_device *dev;
	sync_serial_settings settings;
	void __iomem *base_addr;
	u32 __pad __attribute__ ((aligned (4)));
};

/* GLOBAL registers definitions */
#define GCMDR   0x00
#define GSTAR   0x04
#define GMODE   0x08
#define IQLENR0 0x0C
#define IQLENR1 0x10
#define IQRX0   0x14
#define IQTX0   0x24
#define IQCFG   0x3c
#define FIFOCR1 0x44
#define FIFOCR2 0x48
#define FIFOCR3 0x4c
#define FIFOCR4 0x34
#define CH0CFG  0x50
#define CH0BRDA 0x54
#define CH0BTDA 0x58
#define CH0FRDA 0x98
#define CH0FTDA 0xb0
#define CH0LRDA 0xc8
#define CH0LTDA 0xe0

/* SCC registers definitions */
#define SCC_START	0x0100
#define SCC_OFFSET      0x80
#define CMDR    0x00
#define STAR    0x04
#define CCR0    0x08
#define CCR1    0x0c
#define CCR2    0x10
#define BRR     0x2C
#define RLCR    0x40
#define IMR     0x54
#define ISR     0x58

#define GPDIR	0x0400
#define GPDATA	0x0404
#define GPIM	0x0408

/* Bit masks */
#define EncodingMask	0x00700000
#define CrcMask		0x00000003

#define IntRxScc0	0x10000000
#define IntTxScc0	0x01000000

#define TxPollCmd	0x00000400
#define RxActivate	0x08000000
#define MTFi		0x04000000
#define Rdr		0x00400000
#define Rdt		0x00200000
#define Idr		0x00100000
#define Idt		0x00080000
#define TxSccRes	0x01000000
#define RxSccRes	0x00010000
#define TxSizeMax	0x1fff		/* Datasheet DS1 - 11.1.1.1 */
#define RxSizeMax	0x1ffc		/* Datasheet DS1 - 11.1.2.1 */

#define Ccr0ClockMask	0x0000003f
#define Ccr1LoopMask	0x00000200
#define IsrMask		0x000fffff
#define BrrExpMask	0x00000f00
#define BrrMultMask	0x0000003f
#define EncodingMask	0x00700000
#define Hold		cpu_to_le32(0x40000000)
#define SccBusy		0x10000000
#define PowerUp		0x80000000
#define Vis		0x00001000
#define FrameOk		(FrameVfr | FrameCrc)
#define FrameVfr	0x80
#define FrameRdo	0x40
#define FrameCrc	0x20
#define FrameRab	0x10
#define FrameAborted	cpu_to_le32(0x00000200)
#define FrameEnd	cpu_to_le32(0x80000000)
#define DataComplete	cpu_to_le32(0x40000000)
#define LengthCheck	0x00008000
#define SccEvt		0x02000000
#define NoAck		0x00000200
#define Action		0x00000001
#define HiDesc		cpu_to_le32(0x20000000)

/* SCC events */
#define RxEvt		0xf0000000
#define TxEvt		0x0f000000
#define Alls		0x00040000
#define Xdu		0x00010000
#define Cts		0x00004000
#define Xmr		0x00002000
#define Xpr		0x00001000
#define Rdo		0x00000080
#define Rfs		0x00000040
#define Cd		0x00000004
#define Rfo		0x00000002
#define Flex		0x00000001

/* DMA core events */
#define Cfg		0x00200000
#define Hi		0x00040000
#define Fi		0x00020000
#define Err		0x00010000
#define Arf		0x00000002
#define ArAck		0x00000001

/* State flags */
#define Ready		0x00000000
#define NeedIDR		0x00000001
#define NeedIDT		0x00000002
#define RdoSet		0x00000004
#define FakeReset	0x00000008

/* Don't mask RDO. Ever. */
#ifdef DSCC4_POLLING
#define EventsMask	0xfffeef7f
#else
#define EventsMask	0xfffa8f7a
#endif

/* Functions prototypes */
static void dscc4_rx_irq(struct dscc4_pci_priv *, struct dscc4_dev_priv *);
static void dscc4_tx_irq(struct dscc4_pci_priv *, struct dscc4_dev_priv *);
static int dscc4_found1(struct pci_dev *, void __iomem *ioaddr);
static int dscc4_init_one(struct pci_dev *, const struct pci_device_id *ent);
static int dscc4_open(struct net_device *);
static netdev_tx_t dscc4_start_xmit(struct sk_buff *,
					  struct net_device *);
static int dscc4_close(struct net_device *);
static int dscc4_ioctl(struct net_device *dev, struct ifreq *rq, int cmd);
static int dscc4_init_ring(struct net_device *);
static void dscc4_release_ring(struct dscc4_dev_priv *);
static void dscc4_timer(unsigned long);
static void dscc4_tx_timeout(struct net_device *);
static irqreturn_t dscc4_irq(int irq, void *dev_id);
static int dscc4_hdlc_attach(struct net_device *, unsigned short, unsigned short);
static int dscc4_set_iface(struct dscc4_dev_priv *, struct net_device *);
#ifdef DSCC4_POLLING
static int dscc4_tx_poll(struct dscc4_dev_priv *, struct net_device *);
#endif

static inline struct dscc4_dev_priv *dscc4_priv(struct net_device *dev)
{
	return dev_to_hdlc(dev)->priv;
}

static inline struct net_device *dscc4_to_dev(struct dscc4_dev_priv *p)
{
	return p->dev;
}

static void scc_patchl(u32 mask, u32 value, struct dscc4_dev_priv *dpriv,
			struct net_device *dev, int offset)
{
	u32 state;

	/* Cf scc_writel for concern regarding thread-safety */
	state = dpriv->scc_regs[offset >> 2];
	state &= ~mask;
	state |= value;
	dpriv->scc_regs[offset >> 2] = state;
	writel(state, dpriv->base_addr + SCC_REG_START(dpriv) + offset);
}

static void scc_writel(u32 bits, struct dscc4_dev_priv *dpriv,
		       struct net_device *dev, int offset)
{
	/*
	 * Thread-UNsafe.
	 * As of 2002/02/16, there are no thread racing for access.
	 */
	dpriv->scc_regs[offset >> 2] = bits;
	writel(bits, dpriv->base_addr + SCC_REG_START(dpriv) + offset);
}

static inline u32 scc_readl(struct dscc4_dev_priv *dpriv, int offset)
{
	return dpriv->scc_regs[offset >> 2];
}

static u32 scc_readl_star(struct dscc4_dev_priv *dpriv, struct net_device *dev)
{
	/* Cf errata DS5 p.4 */
	readl(dpriv->base_addr + SCC_REG_START(dpriv) + STAR);
	return readl(dpriv->base_addr + SCC_REG_START(dpriv) + STAR);
}

static inline void dscc4_do_tx(struct dscc4_dev_priv *dpriv,
			       struct net_device *dev)
{
	dpriv->ltda = dpriv->tx_fd_dma +
                      ((dpriv->tx_current-1)%TX_RING_SIZE)*sizeof(struct TxFD);
	writel(dpriv->ltda, dpriv->base_addr + CH0LTDA + dpriv->dev_id*4);
	/* Flush posted writes *NOW* */
	readl(dpriv->base_addr + CH0LTDA + dpriv->dev_id*4);
}

static inline void dscc4_rx_update(struct dscc4_dev_priv *dpriv,
				   struct net_device *dev)
{
	dpriv->lrda = dpriv->rx_fd_dma +
		      ((dpriv->rx_dirty - 1)%RX_RING_SIZE)*sizeof(struct RxFD);
	writel(dpriv->lrda, dpriv->base_addr + CH0LRDA + dpriv->dev_id*4);
}

static inline unsigned int dscc4_tx_done(struct dscc4_dev_priv *dpriv)
{
	return dpriv->tx_current == dpriv->tx_dirty;
}

static inline unsigned int dscc4_tx_quiescent(struct dscc4_dev_priv *dpriv,
					      struct net_device *dev)
{
	return readl(dpriv->base_addr + CH0FTDA + dpriv->dev_id*4) == dpriv->ltda;
}

static int state_check(u32 state, struct dscc4_dev_priv *dpriv,
		       struct net_device *dev, const char *msg)
{
	int ret = 0;

	if (debug > 1) {
	if (SOURCE_ID(state) != dpriv->dev_id) {
		printk(KERN_DEBUG "%s (%s): Source Id=%d, state=%08x\n",
		       dev->name, msg, SOURCE_ID(state), state );
			ret = -1;
	}
	if (state & 0x0df80c00) {
		printk(KERN_DEBUG "%s (%s): state=%08x (UFO alert)\n",
		       dev->name, msg, state);
			ret = -1;
	}
	}
	return ret;
}

static void dscc4_tx_print(struct net_device *dev,
			   struct dscc4_dev_priv *dpriv,
			   char *msg)
{
	printk(KERN_DEBUG "%s: tx_current=%02d tx_dirty=%02d (%s)\n",
	       dev->name, dpriv->tx_current, dpriv->tx_dirty, msg);
}

static void dscc4_release_ring(struct dscc4_dev_priv *dpriv)
{
	struct pci_dev *pdev = dpriv->pci_priv->pdev;
	struct TxFD *tx_fd = dpriv->tx_fd;
	struct RxFD *rx_fd = dpriv->rx_fd;
	struct sk_buff **skbuff;
	int i;

	pci_free_consistent(pdev, TX_TOTAL_SIZE, tx_fd, dpriv->tx_fd_dma);
	pci_free_consistent(pdev, RX_TOTAL_SIZE, rx_fd, dpriv->rx_fd_dma);

	skbuff = dpriv->tx_skbuff;
	for (i = 0; i < TX_RING_SIZE; i++) {
		if (*skbuff) {
			pci_unmap_single(pdev, le32_to_cpu(tx_fd->data),
				(*skbuff)->len, PCI_DMA_TODEVICE);
			dev_kfree_skb(*skbuff);
		}
		skbuff++;
		tx_fd++;
	}

	skbuff = dpriv->rx_skbuff;
	for (i = 0; i < RX_RING_SIZE; i++) {
		if (*skbuff) {
			pci_unmap_single(pdev, le32_to_cpu(rx_fd->data),
				RX_MAX(HDLC_MAX_MRU), PCI_DMA_FROMDEVICE);
			dev_kfree_skb(*skbuff);
		}
		skbuff++;
		rx_fd++;
	}
}

static inline int try_get_rx_skb(struct dscc4_dev_priv *dpriv,
				 struct net_device *dev)
{
	unsigned int dirty = dpriv->rx_dirty%RX_RING_SIZE;
	struct RxFD *rx_fd = dpriv->rx_fd + dirty;
	const int len = RX_MAX(HDLC_MAX_MRU);
	struct sk_buff *skb;
	int ret = 0;

	skb = dev_alloc_skb(len);
	dpriv->rx_skbuff[dirty] = skb;
	if (skb) {
		skb->protocol = hdlc_type_trans(skb, dev);
		rx_fd->data = cpu_to_le32(pci_map_single(dpriv->pci_priv->pdev,
					  skb->data, len, PCI_DMA_FROMDEVICE));
	} else {
		rx_fd->data = 0;
		ret = -1;
	}
	return ret;
}

/*
 * IRQ/thread/whatever safe
 */
static int dscc4_wait_ack_cec(struct dscc4_dev_priv *dpriv,
			      struct net_device *dev, char *msg)
{
	s8 i = 0;

	do {
		if (!(scc_readl_star(dpriv, dev) & SccBusy)) {
			printk(KERN_DEBUG "%s: %s ack (%d try)\n", dev->name,
			       msg, i);
			goto done;
		}
		schedule_timeout_uninterruptible(10);
		rmb();
	} while (++i > 0);
	printk(KERN_ERR "%s: %s timeout\n", dev->name, msg);
done:
	return (i >= 0) ? i : -EAGAIN;
}

static int dscc4_do_action(struct net_device *dev, char *msg)
{
	void __iomem *ioaddr = dscc4_priv(dev)->base_addr;
	s16 i = 0;

	writel(Action, ioaddr + GCMDR);
	ioaddr += GSTAR;
	do {
		u32 state = readl(ioaddr);

		if (state & ArAck) {
			printk(KERN_DEBUG "%s: %s ack\n", dev->name, msg);
			writel(ArAck, ioaddr);
			goto done;
		} else if (state & Arf) {
			printk(KERN_ERR "%s: %s failed\n", dev->name, msg);
			writel(Arf, ioaddr);
			i = -1;
			goto done;
	}
		rmb();
	} while (++i > 0);
	printk(KERN_ERR "%s: %s timeout\n", dev->name, msg);
done:
	return i;
}

static inline int dscc4_xpr_ack(struct dscc4_dev_priv *dpriv)
{
	int cur = dpriv->iqtx_current%IRQ_RING_SIZE;
	s8 i = 0;

	do {
		if (!(dpriv->flags & (NeedIDR | NeedIDT)) ||
		    (dpriv->iqtx[cur] & cpu_to_le32(Xpr)))
			break;
		smp_rmb();
		schedule_timeout_uninterruptible(10);
	} while (++i > 0);

	return (i >= 0 ) ? i : -EAGAIN;
}

#if 0 /* dscc4_{rx/tx}_reset are both unreliable - more tweak needed */
static void dscc4_rx_reset(struct dscc4_dev_priv *dpriv, struct net_device *dev)
{
	unsigned long flags;

	spin_lock_irqsave(&dpriv->pci_priv->lock, flags);
	/* Cf errata DS5 p.6 */
	writel(0x00000000, dpriv->base_addr + CH0LRDA + dpriv->dev_id*4);
	scc_patchl(PowerUp, 0, dpriv, dev, CCR0);
	readl(dpriv->base_addr + CH0LRDA + dpriv->dev_id*4);
	writel(MTFi|Rdr, dpriv->base_addr + dpriv->dev_id*0x0c + CH0CFG);
	writel(Action, dpriv->base_addr + GCMDR);
	spin_unlock_irqrestore(&dpriv->pci_priv->lock, flags);
}

#endif

#if 0
static void dscc4_tx_reset(struct dscc4_dev_priv *dpriv, struct net_device *dev)
{
	u16 i = 0;

	/* Cf errata DS5 p.7 */
	scc_patchl(PowerUp, 0, dpriv, dev, CCR0);
	scc_writel(0x00050000, dpriv, dev, CCR2);
	/*
	 * Must be longer than the time required to fill the fifo.
	 */
	while (!dscc4_tx_quiescent(dpriv, dev) && ++i) {
		udelay(1);
		wmb();
	}

	writel(MTFi|Rdt, dpriv->base_addr + dpriv->dev_id*0x0c + CH0CFG);
	if (dscc4_do_action(dev, "Rdt") < 0)
		printk(KERN_ERR "%s: Tx reset failed\n", dev->name);
}
#endif

/* TODO: (ab)use this function to refill a completely depleted RX ring. */
static inline void dscc4_rx_skb(struct dscc4_dev_priv *dpriv,
				struct net_device *dev)
{
	struct RxFD *rx_fd = dpriv->rx_fd + dpriv->rx_current%RX_RING_SIZE;
	struct pci_dev *pdev = dpriv->pci_priv->pdev;
	struct sk_buff *skb;
	int pkt_len;

	skb = dpriv->rx_skbuff[dpriv->rx_current++%RX_RING_SIZE];
	if (!skb) {
		printk(KERN_DEBUG "%s: skb=0 (%s)\n", dev->name, __func__);
		goto refill;
	}
	pkt_len = TO_SIZE(le32_to_cpu(rx_fd->state2));
	pci_unmap_single(pdev, le32_to_cpu(rx_fd->data),
			 RX_MAX(HDLC_MAX_MRU), PCI_DMA_FROMDEVICE);
	if ((skb->data[--pkt_len] & FrameOk) == FrameOk) {
		dev->stats.rx_packets++;
		dev->stats.rx_bytes += pkt_len;
		skb_put(skb, pkt_len);
		if (netif_running(dev))
			skb->protocol = hdlc_type_trans(skb, dev);
		netif_rx(skb);
	} else {
		if (skb->data[pkt_len] & FrameRdo)
			dev->stats.rx_fifo_errors++;
		else if (!(skb->data[pkt_len] & FrameCrc))
			dev->stats.rx_crc_errors++;
		else if ((skb->data[pkt_len] & (FrameVfr | FrameRab)) !=
			 (FrameVfr | FrameRab))
			dev->stats.rx_length_errors++;
		dev->stats.rx_errors++;
		dev_kfree_skb_irq(skb);
	}
refill:
	while ((dpriv->rx_dirty - dpriv->rx_current) % RX_RING_SIZE) {
		if (try_get_rx_skb(dpriv, dev) < 0)
			break;
		dpriv->rx_dirty++;
	}
	dscc4_rx_update(dpriv, dev);
	rx_fd->state2 = 0x00000000;
	rx_fd->end = cpu_to_le32(0xbabeface);
}

static void dscc4_free1(struct pci_dev *pdev)
{
	struct dscc4_pci_priv *ppriv;
	struct dscc4_dev_priv *root;
	int i;

	ppriv = pci_get_drvdata(pdev);
	root = ppriv->root;

	for (i = 0; i < dev_per_card; i++)
		unregister_hdlc_device(dscc4_to_dev(root + i));

	pci_set_drvdata(pdev, NULL);

	for (i = 0; i < dev_per_card; i++)
		free_netdev(root[i].dev);
	kfree(root);
	kfree(ppriv);
}

static int __devinit dscc4_init_one(struct pci_dev *pdev,
				  const struct pci_device_id *ent)
{
	struct dscc4_pci_priv *priv;
	struct dscc4_dev_priv *dpriv;
	void __iomem *ioaddr;
	int i, rc;

	printk(KERN_DEBUG "%s", version);

	rc = pci_enable_device(pdev);
	if (rc < 0)
		goto out;

	rc = pci_request_region(pdev, 0, "registers");
	if (rc < 0) {
	        printk(KERN_ERR "%s: can't reserve MMIO region (regs)\n",
			DRV_NAME);
	        goto err_disable_0;
	}
	rc = pci_request_region(pdev, 1, "LBI interface");
	if (rc < 0) {
	        printk(KERN_ERR "%s: can't reserve MMIO region (lbi)\n",
			DRV_NAME);
	        goto err_free_mmio_region_1;
	}

	ioaddr = pci_ioremap_bar(pdev, 0);
	if (!ioaddr) {
		printk(KERN_ERR "%s: cannot remap MMIO region %llx @ %llx\n",
			DRV_NAME, (unsigned long long)pci_resource_len(pdev, 0),
			(unsigned long long)pci_resource_start(pdev, 0));
		rc = -EIO;
		goto err_free_mmio_regions_2;
	}
	printk(KERN_DEBUG "Siemens DSCC4, MMIO at %#llx (regs), %#llx (lbi), IRQ %d\n",
	        (unsigned long long)pci_resource_start(pdev, 0),
	        (unsigned long long)pci_resource_start(pdev, 1), pdev->irq);

	/* Cf errata DS5 p.2 */
	pci_write_config_byte(pdev, PCI_LATENCY_TIMER, 0xf8);
	pci_set_master(pdev);

	rc = dscc4_found1(pdev, ioaddr);
	if (rc < 0)
	        goto err_iounmap_3;

	priv = pci_get_drvdata(pdev);

	rc = request_irq(pdev->irq, dscc4_irq, IRQF_SHARED, DRV_NAME, priv->root);
	if (rc < 0) {
		printk(KERN_WARNING "%s: IRQ %d busy\n", DRV_NAME, pdev->irq);
		goto err_release_4;
	}

	/* power up/little endian/dma core controlled via lrda/ltda */
	writel(0x00000001, ioaddr + GMODE);
	/* Shared interrupt queue */
	{
		u32 bits;

		bits = (IRQ_RING_SIZE >> 5) - 1;
		bits |= bits << 4;
		bits |= bits << 8;
		bits |= bits << 16;
		writel(bits, ioaddr + IQLENR0);
	}
	/* Global interrupt queue */
	writel((u32)(((IRQ_RING_SIZE >> 5) - 1) << 20), ioaddr + IQLENR1);
	priv->iqcfg = (__le32 *) pci_alloc_consistent(pdev,
		IRQ_RING_SIZE*sizeof(__le32), &priv->iqcfg_dma);
	if (!priv->iqcfg)
		goto err_free_irq_5;
	writel(priv->iqcfg_dma, ioaddr + IQCFG);

	rc = -ENOMEM;

	/*
	 * SCC 0-3 private rx/tx irq structures
	 * IQRX/TXi needs to be set soon. Learned it the hard way...
	 */
	for (i = 0; i < dev_per_card; i++) {
		dpriv = priv->root + i;
		dpriv->iqtx = (__le32 *) pci_alloc_consistent(pdev,
			IRQ_RING_SIZE*sizeof(u32), &dpriv->iqtx_dma);
		if (!dpriv->iqtx)
			goto err_free_iqtx_6;
		writel(dpriv->iqtx_dma, ioaddr + IQTX0 + i*4);
	}
	for (i = 0; i < dev_per_card; i++) {
		dpriv = priv->root + i;
		dpriv->iqrx = (__le32 *) pci_alloc_consistent(pdev,
			IRQ_RING_SIZE*sizeof(u32), &dpriv->iqrx_dma);
		if (!dpriv->iqrx)
			goto err_free_iqrx_7;
		writel(dpriv->iqrx_dma, ioaddr + IQRX0 + i*4);
	}

	/* Cf application hint. Beware of hard-lock condition on threshold. */
	writel(0x42104000, ioaddr + FIFOCR1);
	//writel(0x9ce69800, ioaddr + FIFOCR2);
	writel(0xdef6d800, ioaddr + FIFOCR2);
	//writel(0x11111111, ioaddr + FIFOCR4);
	writel(0x18181818, ioaddr + FIFOCR4);
	// FIXME: should depend on the chipset revision
	writel(0x0000000e, ioaddr + FIFOCR3);

	writel(0xff200001, ioaddr + GCMDR);

	rc = 0;
out:
	return rc;

err_free_iqrx_7:
	while (--i >= 0) {
		dpriv = priv->root + i;
		pci_free_consistent(pdev, IRQ_RING_SIZE*sizeof(u32),
				    dpriv->iqrx, dpriv->iqrx_dma);
	}
	i = dev_per_card;
err_free_iqtx_6:
	while (--i >= 0) {
		dpriv = priv->root + i;
		pci_free_consistent(pdev, IRQ_RING_SIZE*sizeof(u32),
				    dpriv->iqtx, dpriv->iqtx_dma);
	}
	pci_free_consistent(pdev, IRQ_RING_SIZE*sizeof(u32), priv->iqcfg,
			    priv->iqcfg_dma);
err_free_irq_5:
	free_irq(pdev->irq, priv->root);
err_release_4:
	dscc4_free1(pdev);
err_iounmap_3:
	iounmap (ioaddr);
err_free_mmio_regions_2:
	pci_release_region(pdev, 1);
err_free_mmio_region_1:
	pci_release_region(pdev, 0);
err_disable_0:
	pci_disable_device(pdev);
	goto out;
};

/*
 * Let's hope the default values are decent enough to protect my
 * feet from the user's gun - Ueimor
 */
static void dscc4_init_registers(struct dscc4_dev_priv *dpriv,
				 struct net_device *dev)
{
	/* No interrupts, SCC core disabled. Let's relax */
	scc_writel(0x00000000, dpriv, dev, CCR0);

	scc_writel(LengthCheck | (HDLC_MAX_MRU >> 5), dpriv, dev, RLCR);

	/*
	 * No address recognition/crc-CCITT/cts enabled
	 * Shared flags transmission disabled - cf errata DS5 p.11
	 * Carrier detect disabled - cf errata p.14
	 * FIXME: carrier detection/polarity may be handled more gracefully.
	 */
	scc_writel(0x02408000, dpriv, dev, CCR1);

	/* crc not forwarded - Cf errata DS5 p.11 */
	scc_writel(0x00050008 & ~RxActivate, dpriv, dev, CCR2);
	// crc forwarded
	//scc_writel(0x00250008 & ~RxActivate, dpriv, dev, CCR2);
}

static inline int dscc4_set_quartz(struct dscc4_dev_priv *dpriv, int hz)
{
	int ret = 0;

	if ((hz < 0) || (hz > DSCC4_HZ_MAX))
		ret = -EOPNOTSUPP;
	else
		dpriv->pci_priv->xtal_hz = hz;

	return ret;
}

static const struct net_device_ops dscc4_ops = {
	.ndo_open       = dscc4_open,
	.ndo_stop       = dscc4_close,
	.ndo_change_mtu = hdlc_change_mtu,
	.ndo_start_xmit = hdlc_start_xmit,
	.ndo_do_ioctl   = dscc4_ioctl,
	.ndo_tx_timeout = dscc4_tx_timeout,
};

static int dscc4_found1(struct pci_dev *pdev, void __iomem *ioaddr)
{
	struct dscc4_pci_priv *ppriv;
	struct dscc4_dev_priv *root;
	int i, ret = -ENOMEM;

	root = kcalloc(dev_per_card, sizeof(*root), GFP_KERNEL);
	if (!root) {
		printk(KERN_ERR "%s: can't allocate data\n", DRV_NAME);
		goto err_out;
	}

	for (i = 0; i < dev_per_card; i++) {
		root[i].dev = alloc_hdlcdev(root + i);
		if (!root[i].dev)
			goto err_free_dev;
	}

	ppriv = kzalloc(sizeof(*ppriv), GFP_KERNEL);
	if (!ppriv) {
		printk(KERN_ERR "%s: can't allocate private data\n", DRV_NAME);
		goto err_free_dev;
	}

	ppriv->root = root;
	spin_lock_init(&ppriv->lock);

	for (i = 0; i < dev_per_card; i++) {
		struct dscc4_dev_priv *dpriv = root + i;
		struct net_device *d = dscc4_to_dev(dpriv);
		hdlc_device *hdlc = dev_to_hdlc(d);

	        d->base_addr = (unsigned long)ioaddr;
	        d->irq = pdev->irq;
		d->netdev_ops = &dscc4_ops;
		d->watchdog_timeo = TX_TIMEOUT;
		SET_NETDEV_DEV(d, &pdev->dev);

		dpriv->dev_id = i;
		dpriv->pci_priv = ppriv;
		dpriv->base_addr = ioaddr;
		spin_lock_init(&dpriv->lock);

		hdlc->xmit = dscc4_start_xmit;
		hdlc->attach = dscc4_hdlc_attach;

		dscc4_init_registers(dpriv, d);
		dpriv->parity = PARITY_CRC16_PR0_CCITT;
		dpriv->encoding = ENCODING_NRZ;
	
		ret = dscc4_init_ring(d);
		if (ret < 0)
			goto err_unregister;

		ret = register_hdlc_device(d);
		if (ret < 0) {
			printk(KERN_ERR "%s: unable to register\n", DRV_NAME);
			dscc4_release_ring(dpriv);
			goto err_unregister;
	        }
	}

	ret = dscc4_set_quartz(root, quartz);
	if (ret < 0)
		goto err_unregister;

	pci_set_drvdata(pdev, ppriv);
	return ret;

err_unregister:
	while (i-- > 0) {
		dscc4_release_ring(root + i);
		unregister_hdlc_device(dscc4_to_dev(root + i));
	}
	kfree(ppriv);
	i = dev_per_card;
err_free_dev:
	while (i-- > 0)
		free_netdev(root[i].dev);
	kfree(root);
err_out:
	return ret;
};

/* FIXME: get rid of the unneeded code */
static void dscc4_timer(unsigned long data)
{
	struct net_device *dev = (struct net_device *)data;
	struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
//	struct dscc4_pci_priv *ppriv;

	goto done;
done:
        dpriv->timer.expires = jiffies + TX_TIMEOUT;
        add_timer(&dpriv->timer);
}

static void dscc4_tx_timeout(struct net_device *dev)
{
	/* FIXME: something is missing there */
}

static int dscc4_loopback_check(struct dscc4_dev_priv *dpriv)
{
	sync_serial_settings *settings = &dpriv->settings;

	if (settings->loopback && (settings->clock_type != CLOCK_INT)) {
		struct net_device *dev = dscc4_to_dev(dpriv);

		printk(KERN_INFO "%s: loopback requires clock\n", dev->name);
		return -1;
	}
	return 0;
}

#ifdef CONFIG_DSCC4_PCI_RST
/*
 * Some DSCC4-based cards wires the GPIO port and the PCI #RST pin together
 * so as to provide a safe way to reset the asic while not the whole machine
 * rebooting.
 *
 * This code doesn't need to be efficient. Keep It Simple
 */
static void dscc4_pci_reset(struct pci_dev *pdev, void __iomem *ioaddr)
{
	int i;

	mutex_lock(&dscc4_mutex);
	for (i = 0; i < 16; i++)
		pci_read_config_dword(pdev, i << 2, dscc4_pci_config_store + i);

	/* Maximal LBI clock divider (who cares ?) and whole GPIO range. */
	writel(0x001c0000, ioaddr + GMODE);
	/* Configure GPIO port as output */
	writel(0x0000ffff, ioaddr + GPDIR);
	/* Disable interruption */
	writel(0x0000ffff, ioaddr + GPIM);

	writel(0x0000ffff, ioaddr + GPDATA);
	writel(0x00000000, ioaddr + GPDATA);

	/* Flush posted writes */
	readl(ioaddr + GSTAR);

	schedule_timeout_uninterruptible(10);

	for (i = 0; i < 16; i++)
		pci_write_config_dword(pdev, i << 2, dscc4_pci_config_store[i]);
	mutex_unlock(&dscc4_mutex);
}
#else
#define dscc4_pci_reset(pdev,ioaddr)	do {} while (0)
#endif /* CONFIG_DSCC4_PCI_RST */

static int dscc4_open(struct net_device *dev)
{
	struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
	struct dscc4_pci_priv *ppriv;
	int ret = -EAGAIN;

	if ((dscc4_loopback_check(dpriv) < 0))
		goto err;

	if ((ret = hdlc_open(dev)))
		goto err;

	ppriv = dpriv->pci_priv;

	/*
	 * Due to various bugs, there is no way to reliably reset a
	 * specific port (manufacturer's dependant special PCI #RST wiring
	 * apart: it affects all ports). Thus the device goes in the best
	 * silent mode possible at dscc4_close() time and simply claims to
	 * be up if it's opened again. It still isn't possible to change
	 * the HDLC configuration without rebooting but at least the ports
	 * can be up/down ifconfig'ed without killing the host.
	 */
	if (dpriv->flags & FakeReset) {
		dpriv->flags &= ~FakeReset;
		scc_patchl(0, PowerUp, dpriv, dev, CCR0);
		scc_patchl(0, 0x00050000, dpriv, dev, CCR2);
		scc_writel(EventsMask, dpriv, dev, IMR);
		printk(KERN_INFO "%s: up again.\n", dev->name);
		goto done;
	}

	/* IDT+IDR during XPR */
	dpriv->flags = NeedIDR | NeedIDT;

	scc_patchl(0, PowerUp | Vis, dpriv, dev, CCR0);

	/*
	 * The following is a bit paranoid...
	 *
	 * NB: the datasheet "...CEC will stay active if the SCC is in
	 * power-down mode or..." and CCR2.RAC = 1 are two different
	 * situations.
	 */
	if (scc_readl_star(dpriv, dev) & SccBusy) {
		printk(KERN_ERR "%s busy. Try later\n", dev->name);
		ret = -EAGAIN;
		goto err_out;
	} else
		printk(KERN_INFO "%s: available. Good\n", dev->name);

	scc_writel(EventsMask, dpriv, dev, IMR);

	/* Posted write is flushed in the wait_ack loop */
	scc_writel(TxSccRes | RxSccRes, dpriv, dev, CMDR);

	if ((ret = dscc4_wait_ack_cec(dpriv, dev, "Cec")) < 0)
		goto err_disable_scc_events;

	/*
	 * I would expect XPR near CE completion (before ? after ?).
	 * At worst, this code won't see a late XPR and people
	 * will have to re-issue an ifconfig (this is harmless).
	 * WARNING, a really missing XPR usually means a hardware
	 * reset is needed. Suggestions anyone ?
	 */
	if ((ret = dscc4_xpr_ack(dpriv)) < 0) {
		printk(KERN_ERR "%s: %s timeout\n", DRV_NAME, "XPR");
		goto err_disable_scc_events;
	}
	
	if (debug > 2)
		dscc4_tx_print(dev, dpriv, "Open");

done:
	netif_start_queue(dev);

        init_timer(&dpriv->timer);
        dpriv->timer.expires = jiffies + 10*HZ;
        dpriv->timer.data = (unsigned long)dev;
	dpriv->timer.function = dscc4_timer;
        add_timer(&dpriv->timer);
	netif_carrier_on(dev);

	return 0;

err_disable_scc_events:
	scc_writel(0xffffffff, dpriv, dev, IMR);
	scc_patchl(PowerUp | Vis, 0, dpriv, dev, CCR0);
err_out:
	hdlc_close(dev);
err:
	return ret;
}

#ifdef DSCC4_POLLING
static int dscc4_tx_poll(struct dscc4_dev_priv *dpriv, struct net_device *dev)
{
	/* FIXME: it's gonna be easy (TM), for sure */
}
#endif /* DSCC4_POLLING */

static netdev_tx_t dscc4_start_xmit(struct sk_buff *skb,
					  struct net_device *dev)
{
	struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
	struct dscc4_pci_priv *ppriv = dpriv->pci_priv;
	struct TxFD *tx_fd;
	int next;

	next = dpriv->tx_current%TX_RING_SIZE;
	dpriv->tx_skbuff[next] = skb;
	tx_fd = dpriv->tx_fd + next;
	tx_fd->state = FrameEnd | TO_STATE_TX(skb->len);
	tx_fd->data = cpu_to_le32(pci_map_single(ppriv->pdev, skb->data, skb->len,
				     PCI_DMA_TODEVICE));
	tx_fd->complete = 0x00000000;
	tx_fd->jiffies = jiffies;
	mb();

#ifdef DSCC4_POLLING
	spin_lock(&dpriv->lock);
	while (dscc4_tx_poll(dpriv, dev));
	spin_unlock(&dpriv->lock);
#endif

	if (debug > 2)
		dscc4_tx_print(dev, dpriv, "Xmit");
	/* To be cleaned(unsigned int)/optimized. Later, ok ? */
	if (!((++dpriv->tx_current - dpriv->tx_dirty)%TX_RING_SIZE))
		netif_stop_queue(dev);

	if (dscc4_tx_quiescent(dpriv, dev))
		dscc4_do_tx(dpriv, dev);

	return NETDEV_TX_OK;
}

static int dscc4_close(struct net_device *dev)
{
	struct dscc4_dev_priv *dpriv = dscc4_priv(dev);

	del_timer_sync(&dpriv->timer);
	netif_stop_queue(dev);

	scc_patchl(PowerUp | Vis, 0, dpriv, dev, CCR0);
	scc_patchl(0x00050000, 0, dpriv, dev, CCR2);
	scc_writel(0xffffffff, dpriv, dev, IMR);

	dpriv->flags |= FakeReset;

	hdlc_close(dev);

	return 0;
}

static inline int dscc4_check_clock_ability(int port)
{
	int ret = 0;

#ifdef CONFIG_DSCC4_PCISYNC
	if (port >= 2)
		ret = -1;
#endif
	return ret;
}

/*
 * DS1 p.137: "There are a total of 13 different clocking modes..."
 *                                  ^^
 * Design choices:
 * - by default, assume a clock is provided on pin RxClk/TxClk (clock mode 0a).
 *   Clock mode 3b _should_ work but the testing seems to make this point
 *   dubious (DIY testing requires setting CCR0 at 0x00000033).
 *   This is supposed to provide least surprise "DTE like" behavior.
 * - if line rate is specified, clocks are assumed to be locally generated.
 *   A quartz must be available (on pin XTAL1). Modes 6b/7b are used. Choosing
 *   between these it automagically done according on the required frequency
 *   scaling. Of course some rounding may take place.
 * - no high speed mode (40Mb/s). May be trivial to do but I don't have an
 *   appropriate external clocking device for testing.
 * - no time-slot/clock mode 5: shameless lazyness.
 *
 * The clock signals wiring can be (is ?) manufacturer dependant. Good luck.
 *
 * BIG FAT WARNING: if the device isn't provided enough clocking signal, it
 * won't pass the init sequence. For example, straight back-to-back DTE without
 * external clock will fail when dscc4_open() (<- 'ifconfig hdlcx xxx') is
 * called.
 *
 * Typos lurk in datasheet (missing divier in clock mode 7a figure 51 p.153
 * DS0 for example)
 *
 * Clock mode related bits of CCR0:
 *     +------------ TOE: output TxClk (0b/2b/3a/3b/6b/7a/7b only)
 *     | +---------- SSEL: sub-mode select 0 -> a, 1 -> b
 *     | | +-------- High Speed: say 0
 *     | | | +-+-+-- Clock Mode: 0..7
 *     | | | | | |
 * -+-+-+-+-+-+-+-+
 * x|x|5|4|3|2|1|0| lower bits
 *
 * Division factor of BRR: k = (N+1)x2^M (total divider = 16xk in mode 6b)
 *            +-+-+-+------------------ M (0..15)
 *            | | | |     +-+-+-+-+-+-- N (0..63)
 *    0 0 0 0 | | | | 0 0 | | | | | |
 * ...-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    f|e|d|c|b|a|9|8|7|6|5|4|3|2|1|0| lower bits
 *
 */
static int dscc4_set_clock(struct net_device *dev, u32 *bps, u32 *state)
{
	struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
	int ret = -1;
	u32 brr;

	*state &= ~Ccr0ClockMask;
	if (*bps) { /* Clock generated - required for DCE */
		u32 n = 0, m = 0, divider;
		int xtal;

		xtal = dpriv->pci_priv->xtal_hz;
		if (!xtal)
			goto done;
		if (dscc4_check_clock_ability(dpriv->dev_id) < 0)
			goto done;
		divider = xtal / *bps;
		if (divider > BRR_DIVIDER_MAX) {
			divider >>= 4;
			*state |= 0x00000036; /* Clock mode 6b (BRG/16) */
		} else
			*state |= 0x00000037; /* Clock mode 7b (BRG) */
		if (divider >> 22) {
			n = 63;
			m = 15;
		} else if (divider) {
			/* Extraction of the 6 highest weighted bits */
			m = 0;
			while (0xffffffc0 & divider) {
				m++;
				divider >>= 1;
			}
			n = divider;
		}
		brr = (m << 8) | n;
		divider = n << m;
		if (!(*state & 0x00000001)) /* ?b mode mask => clock mode 6b */
			divider <<= 4;
		*bps = xtal / divider;
	} else {
		/*
		 * External clock - DTE
		 * "state" already reflects Clock mode 0a (CCR0 = 0xzzzzzz00).
		 * Nothing more to be done
		 */
		brr = 0;
	}
	scc_writel(brr, dpriv, dev, BRR);
	ret = 0;
done:
	return ret;
}

static int dscc4_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
	sync_serial_settings __user *line = ifr->ifr_settings.ifs_ifsu.sync;
	struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
	const size_t size = sizeof(dpriv->settings);
	int ret = 0;

        if (dev->flags & IFF_UP)
                return -EBUSY;

	if (cmd != SIOCWANDEV)
		return -EOPNOTSUPP;

	switch(ifr->ifr_settings.type) {
	case IF_GET_IFACE:
		ifr->ifr_settings.type = IF_IFACE_SYNC_SERIAL;
		if (ifr->ifr_settings.size < size) {
			ifr->ifr_settings.size = size; /* data size wanted */
			return -ENOBUFS;
		}
		if (copy_to_user(line, &dpriv->settings, size))
			return -EFAULT;
		break;

	case IF_IFACE_SYNC_SERIAL:
		if (!capable(CAP_NET_ADMIN))
			return -EPERM;

		if (dpriv->flags & FakeReset) {
			printk(KERN_INFO "%s: please reset the device"
			       " before this command\n", dev->name);
			return -EPERM;
		}
		if (copy_from_user(&dpriv->settings, line, size))
			return -EFAULT;
		ret = dscc4_set_iface(dpriv, dev);
		break;

	default:
		ret = hdlc_ioctl(dev, ifr, cmd);
		break;
	}

	return ret;
}

static int dscc4_match(const struct thingie *p, int value)
{
	int i;

	for (i = 0; p[i].define != -1; i++) {
		if (value == p[i].define)
			break;
	}
	if (p[i].define == -1)
		return -1;
	else
		return i;
}

static int dscc4_clock_setting(struct dscc4_dev_priv *dpriv,
			       struct net_device *dev)
{
	sync_serial_settings *settings = &dpriv->settings;
	int ret = -EOPNOTSUPP;
	u32 bps, state;

	bps = settings->clock_rate;
	state = scc_readl(dpriv, CCR0);
	if (dscc4_set_clock(dev, &bps, &state) < 0)
		goto done;
	if (bps) { /* DCE */
		printk(KERN_DEBUG "%s: generated RxClk (DCE)\n", dev->name);
		if (settings->clock_rate != bps) {
			printk(KERN_DEBUG "%s: clock adjusted (%08d -> %08d)\n",
				dev->name, settings->clock_rate, bps);
			settings->clock_rate = bps;
		}
	} else { /* DTE */
		state |= PowerUp | Vis;
		printk(KERN_DEBUG "%s: external RxClk (DTE)\n", dev->name);
	}
	scc_writel(state, dpriv, dev, CCR0);
	ret = 0;
done:
	return ret;
}

static int dscc4_encoding_setting(struct dscc4_dev_priv *dpriv,
				  struct net_device *dev)
{
	static const struct thingie encoding[] = {
		{ ENCODING_NRZ,		0x00000000 },
		{ ENCODING_NRZI,	0x00200000 },
		{ ENCODING_FM_MARK,	0x00400000 },
		{ ENCODING_FM_SPACE,	0x00500000 },
		{ ENCODING_MANCHESTER,	0x00600000 },
		{ -1,			0}
	};
	int i, ret = 0;

	i = dscc4_match(encoding, dpriv->encoding);
	if (i >= 0)
		scc_patchl(EncodingMask, encoding[i].bits, dpriv, dev, CCR0);
	else
		ret = -EOPNOTSUPP;
	return ret;
}

static int dscc4_loopback_setting(struct dscc4_dev_priv *dpriv,
				  struct net_device *dev)
{
	sync_serial_settings *settings = &dpriv->settings;
	u32 state;

	state = scc_readl(dpriv, CCR1);
	if (settings->loopback) {
		printk(KERN_DEBUG "%s: loopback\n", dev->name);
		state |= 0x00000100;
	} else {
		printk(KERN_DEBUG "%s: normal\n", dev->name);
		state &= ~0x00000100;
	}
	scc_writel(state, dpriv, dev, CCR1);
	return 0;
}

static int dscc4_crc_setting(struct dscc4_dev_priv *dpriv,
			     struct net_device *dev)
{
	static const struct thingie crc[] = {
		{ PARITY_CRC16_PR0_CCITT,	0x00000010 },
		{ PARITY_CRC16_PR1_CCITT,	0x00000000 },
		{ PARITY_CRC32_PR0_CCITT,	0x00000011 },
		{ PARITY_CRC32_PR1_CCITT,	0x00000001 }
	};
	int i, ret = 0;

	i = dscc4_match(crc, dpriv->parity);
	if (i >= 0)
		scc_patchl(CrcMask, crc[i].bits, dpriv, dev, CCR1);
	else
		ret = -EOPNOTSUPP;
	return ret;
}

static int dscc4_set_iface(struct dscc4_dev_priv *dpriv, struct net_device *dev)
{
	struct {
		int (*action)(struct dscc4_dev_priv *, struct net_device *);
	} *p, do_setting[] = {
		{ dscc4_encoding_setting },
		{ dscc4_clock_setting },
		{ dscc4_loopback_setting },
		{ dscc4_crc_setting },
		{ NULL }
	};
	int ret = 0;

	for (p = do_setting; p->action; p++) {
		if ((ret = p->action(dpriv, dev)) < 0)
			break;
	}
	return ret;
}

static irqreturn_t dscc4_irq(int irq, void *token)
{
	struct dscc4_dev_priv *root = token;
	struct dscc4_pci_priv *priv;
	struct net_device *dev;
	void __iomem *ioaddr;
	u32 state;
	unsigned long flags;
	int i, handled = 1;

	priv = root->pci_priv;
	dev = dscc4_to_dev(root);

	spin_lock_irqsave(&priv->lock, flags);

	ioaddr = root->base_addr;

	state = readl(ioaddr + GSTAR);
	if (!state) {
		handled = 0;
		goto out;
	}
	if (debug > 3)
		printk(KERN_DEBUG "%s: GSTAR = 0x%08x\n", DRV_NAME, state);
	writel(state, ioaddr + GSTAR);

	if (state & Arf) {
		printk(KERN_ERR "%s: failure (Arf). Harass the maintener\n",
		       dev->name);
		goto out;
	}
	state &= ~ArAck;
	if (state & Cfg) {
		if (debug > 0)
			printk(KERN_DEBUG "%s: CfgIV\n", DRV_NAME);
		if (priv->iqcfg[priv->cfg_cur++%IRQ_RING_SIZE] & cpu_to_le32(Arf))
			printk(KERN_ERR "%s: %s failed\n", dev->name, "CFG");
		if (!(state &= ~Cfg))
			goto out;
	}
	if (state & RxEvt) {
		i = dev_per_card - 1;
		do {
			dscc4_rx_irq(priv, root + i);
		} while (--i >= 0);
		state &= ~RxEvt;
	}
	if (state & TxEvt) {
		i = dev_per_card - 1;
		do {
			dscc4_tx_irq(priv, root + i);
		} while (--i >= 0);
		state &= ~TxEvt;
	}
out:
	spin_unlock_irqrestore(&priv->lock, flags);
	return IRQ_RETVAL(handled);
}

static void dscc4_tx_irq(struct dscc4_pci_priv *ppriv,
				struct dscc4_dev_priv *dpriv)
{
	struct net_device *dev = dscc4_to_dev(dpriv);
	u32 state;
	int cur, loop = 0;

try:
	cur = dpriv->iqtx_current%IRQ_RING_SIZE;
	state = le32_to_cpu(dpriv->iqtx[cur]);
	if (!state) {
		if (debug > 4)
			printk(KERN_DEBUG "%s: Tx ISR = 0x%08x\n", dev->name,
			       state);
		if ((debug > 1) && (loop > 1))
			printk(KERN_DEBUG "%s: Tx irq loop=%d\n", dev->name, loop);
		if (loop && netif_queue_stopped(dev))
			if ((dpriv->tx_current - dpriv->tx_dirty)%TX_RING_SIZE)
				netif_wake_queue(dev);

		if (netif_running(dev) && dscc4_tx_quiescent(dpriv, dev) &&
		    !dscc4_tx_done(dpriv))
				dscc4_do_tx(dpriv, dev);
		return;
	}
	loop++;
	dpriv->iqtx[cur] = 0;
	dpriv->iqtx_current++;

	if (state_check(state, dpriv, dev, "Tx") < 0)
		return;

	if (state & SccEvt) {
		if (state & Alls) {
			struct sk_buff *skb;
			struct TxFD *tx_fd;

			if (debug > 2)
				dscc4_tx_print(dev, dpriv, "Alls");
			/*
			 * DataComplete can't be trusted for Tx completion.
			 * Cf errata DS5 p.8
			 */
			cur = dpriv->tx_dirty%TX_RING_SIZE;
			tx_fd = dpriv->tx_fd + cur;
			skb = dpriv->tx_skbuff[cur];
			if (skb) {
				pci_unmap_single(ppriv->pdev, le32_to_cpu(tx_fd->data),
						 skb->len, PCI_DMA_TODEVICE);
				if (tx_fd->state & FrameEnd) {
					dev->stats.tx_packets++;
					dev->stats.tx_bytes += skb->len;
				}
				dev_kfree_skb_irq(skb);
				dpriv->tx_skbuff[cur] = NULL;
				++dpriv->tx_dirty;
			} else {
				if (debug > 1)
					printk(KERN_ERR "%s Tx: NULL skb %d\n",
						dev->name, cur);
			}
			/*
			 * If the driver ends sending crap on the wire, it
			 * will be way easier to diagnose than the (not so)
			 * random freeze induced by null sized tx frames.
			 */
			tx_fd->data = tx_fd->next;
			tx_fd->state = FrameEnd | TO_STATE_TX(2*DUMMY_SKB_SIZE);
			tx_fd->complete = 0x00000000;
			tx_fd->jiffies = 0;

			if (!(state &= ~Alls))
				goto try;
		}
		/*
		 * Transmit Data Underrun
		 */
		if (state & Xdu) {
			printk(KERN_ERR "%s: XDU. Ask maintainer\n", DRV_NAME);
			dpriv->flags = NeedIDT;
			/* Tx reset */
			writel(MTFi | Rdt,
			       dpriv->base_addr + 0x0c*dpriv->dev_id + CH0CFG);
			writel(Action, dpriv->base_addr + GCMDR);
			return;
		}
		if (state & Cts) {
			printk(KERN_INFO "%s: CTS transition\n", dev->name);
			if (!(state &= ~Cts)) /* DEBUG */
				goto try;
		}
		if (state & Xmr) {
			/* Frame needs to be sent again - FIXME */
			printk(KERN_ERR "%s: Xmr. Ask maintainer\n", DRV_NAME);
			if (!(state &= ~Xmr)) /* DEBUG */
				goto try;
		}
		if (state & Xpr) {
			void __iomem *scc_addr;
			unsigned long ring;
			int i;

			/*
			 * - the busy condition happens (sometimes);
			 * - it doesn't seem to make the handler unreliable.
			 */
			for (i = 1; i; i <<= 1) {
				if (!(scc_readl_star(dpriv, dev) & SccBusy))
					break;
			}
			if (!i)
				printk(KERN_INFO "%s busy in irq\n", dev->name);

			scc_addr = dpriv->base_addr + 0x0c*dpriv->dev_id;
			/* Keep this order: IDT before IDR */
			if (dpriv->flags & NeedIDT) {
				if (debug > 2)
					dscc4_tx_print(dev, dpriv, "Xpr");
				ring = dpriv->tx_fd_dma +
				       (dpriv->tx_dirty%TX_RING_SIZE)*
				       sizeof(struct TxFD);
				writel(ring, scc_addr + CH0BTDA);
				dscc4_do_tx(dpriv, dev);
				writel(MTFi | Idt, scc_addr + CH0CFG);
				if (dscc4_do_action(dev, "IDT") < 0)
					goto err_xpr;
				dpriv->flags &= ~NeedIDT;
			}
			if (dpriv->flags & NeedIDR) {
				ring = dpriv->rx_fd_dma +
				       (dpriv->rx_current%RX_RING_SIZE)*
				       sizeof(struct RxFD);
				writel(ring, scc_addr + CH0BRDA);
				dscc4_rx_update(dpriv, dev);
				writel(MTFi | Idr, scc_addr + CH0CFG);
				if (dscc4_do_action(dev, "IDR") < 0)
					goto err_xpr;
				dpriv->flags &= ~NeedIDR;
				smp_wmb();
				/* Activate receiver and misc */
				scc_writel(0x08050008, dpriv, dev, CCR2);
			}
		err_xpr:
			if (!(state &= ~Xpr))
				goto try;
		}
		if (state & Cd) {
			if (debug > 0)
				printk(KERN_INFO "%s: CD transition\n", dev->name);
			if (!(state &= ~Cd)) /* DEBUG */
				goto try;
		}
	} else { /* ! SccEvt */
		if (state & Hi) {
#ifdef DSCC4_POLLING
			while (!dscc4_tx_poll(dpriv, dev));
#endif
			printk(KERN_INFO "%s: Tx Hi\n", dev->name);
			state &= ~Hi;
		}
		if (state & Err) {
			printk(KERN_INFO "%s: Tx ERR\n", dev->name);
			dev->stats.tx_errors++;
			state &= ~Err;
		}
	}
	goto try;
}

static void dscc4_rx_irq(struct dscc4_pci_priv *priv,
				    struct dscc4_dev_priv *dpriv)
{
	struct net_device *dev = dscc4_to_dev(dpriv);
	u32 state;
	int cur;

try:
	cur = dpriv->iqrx_current%IRQ_RING_SIZE;
	state = le32_to_cpu(dpriv->iqrx[cur]);
	if (!state)
		return;
	dpriv->iqrx[cur] = 0;
	dpriv->iqrx_current++;

	if (state_check(state, dpriv, dev, "Rx") < 0)
		return;

	if (!(state & SccEvt)){
		struct RxFD *rx_fd;

		if (debug > 4)
			printk(KERN_DEBUG "%s: Rx ISR = 0x%08x\n", dev->name,
			       state);
		state &= 0x00ffffff;
		if (state & Err) { /* Hold or reset */
			printk(KERN_DEBUG "%s: Rx ERR\n", dev->name);
			cur = dpriv->rx_current%RX_RING_SIZE;
			rx_fd = dpriv->rx_fd + cur;
			/*
			 * Presume we're not facing a DMAC receiver reset.
			 * As We use the rx size-filtering feature of the
			 * DSCC4, the beginning of a new frame is waiting in
			 * the rx fifo. I bet a Receive Data Overflow will
			 * happen most of time but let's try and avoid it.
			 * Btw (as for RDO) if one experiences ERR whereas
			 * the system looks rather idle, there may be a
			 * problem with latency. In this case, increasing
			 * RX_RING_SIZE may help.
			 */
			//while (dpriv->rx_needs_refill) {
				while (!(rx_fd->state1 & Hold)) {
					rx_fd++;
					cur++;
					if (!(cur = cur%RX_RING_SIZE))
						rx_fd = dpriv->rx_fd;
				}
				//dpriv->rx_needs_refill--;
				try_get_rx_skb(dpriv, dev);
				if (!rx_fd->data)
					goto try;
				rx_fd->state1 &= ~Hold;
				rx_fd->state2 = 0x00000000;
				rx_fd->end = cpu_to_le32(0xbabeface);
			//}
			goto try;
		}
		if (state & Fi) {
			dscc4_rx_skb(dpriv, dev);
			goto try;
		}
		if (state & Hi ) { /* HI bit */
			printk(KERN_INFO "%s: Rx Hi\n", dev->name);
			state &= ~Hi;
			goto try;
		}
	} else { /* SccEvt */
		if (debug > 1) {
			//FIXME: verifier la presence de tous les evenements
		static struct {
			u32 mask;
			const char *irq_name;
		} evts[] = {
			{ 0x00008000, "TIN"},
			{ 0x00000020, "RSC"},
			{ 0x00000010, "PCE"},
			{ 0x00000008, "PLLA"},
			{ 0, NULL}
		}, *evt;

		for (evt = evts; evt->irq_name; evt++) {
			if (state & evt->mask) {
					printk(KERN_DEBUG "%s: %s\n",
						dev->name, evt->irq_name);
				if (!(state &= ~evt->mask))
					goto try;
			}
		}
		} else {
			if (!(state &= ~0x0000c03c))
				goto try;
		}
		if (state & Cts) {
			printk(KERN_INFO "%s: CTS transition\n", dev->name);
			if (!(state &= ~Cts)) /* DEBUG */
				goto try;
		}
		/*
		 * Receive Data Overflow (FIXME: fscked)
		 */
		if (state & Rdo) {
			struct RxFD *rx_fd;
			void __iomem *scc_addr;
			int cur;

			//if (debug)
			//	dscc4_rx_dump(dpriv);
			scc_addr = dpriv->base_addr + 0x0c*dpriv->dev_id;

			scc_patchl(RxActivate, 0, dpriv, dev, CCR2);
			/*
			 * This has no effect. Why ?
			 * ORed with TxSccRes, one sees the CFG ack (for
			 * the TX part only).
			 */
			scc_writel(RxSccRes, dpriv, dev, CMDR);
			dpriv->flags |= RdoSet;

			/*
			 * Let's try and save something in the received data.
			 * rx_current must be incremented at least once to
			 * avoid HOLD in the BRDA-to-be-pointed desc.
			 */
			do {
				cur = dpriv->rx_current++%RX_RING_SIZE;
				rx_fd = dpriv->rx_fd + cur;
				if (!(rx_fd->state2 & DataComplete))
					break;
				if (rx_fd->state2 & FrameAborted) {
					dev->stats.rx_over_errors++;
					rx_fd->state1 |= Hold;
					rx_fd->state2 = 0x00000000;
					rx_fd->end = cpu_to_le32(0xbabeface);
				} else
					dscc4_rx_skb(dpriv, dev);
			} while (1);

			if (debug > 0) {
				if (dpriv->flags & RdoSet)
					printk(KERN_DEBUG
					       "%s: no RDO in Rx data\n", DRV_NAME);
			}
#ifdef DSCC4_RDO_EXPERIMENTAL_RECOVERY
			/*
			 * FIXME: must the reset be this violent ?
			 */
#warning "FIXME: CH0BRDA"
			writel(dpriv->rx_fd_dma +
			       (dpriv->rx_current%RX_RING_SIZE)*
			       sizeof(struct RxFD), scc_addr + CH0BRDA);
			writel(MTFi|Rdr|Idr, scc_addr + CH0CFG);
			if (dscc4_do_action(dev, "RDR") < 0) {
				printk(KERN_ERR "%s: RDO recovery failed(%s)\n",
				       dev->name, "RDR");
				goto rdo_end;
			}
			writel(MTFi|Idr, scc_addr + CH0CFG);
			if (dscc4_do_action(dev, "IDR") < 0) {
				printk(KERN_ERR "%s: RDO recovery failed(%s)\n",
				       dev->name, "IDR");
				goto rdo_end;
			}
		rdo_end:
#endif
			scc_patchl(0, RxActivate, dpriv, dev, CCR2);
			goto try;
		}
		if (state & Cd) {
			printk(KERN_INFO "%s: CD transition\n", dev->name);
			if (!(state &= ~Cd)) /* DEBUG */
				goto try;
		}
		if (state & Flex) {
			printk(KERN_DEBUG "%s: Flex. Ttttt...\n", DRV_NAME);
			if (!(state &= ~Flex))
				goto try;
		}
	}
}

/*
 * I had expected the following to work for the first descriptor
 * (tx_fd->state = 0xc0000000)
 * - Hold=1 (don't try and branch to the next descripto);
 * - No=0 (I want an empty data section, i.e. size=0);
 * - Fe=1 (required by No=0 or we got an Err irq and must reset).
 * It failed and locked solid. Thus the introduction of a dummy skb.
 * Problem is acknowledged in errata sheet DS5. Joy :o/
 */
static struct sk_buff *dscc4_init_dummy_skb(struct dscc4_dev_priv *dpriv)
{
	struct sk_buff *skb;

	skb = dev_alloc_skb(DUMMY_SKB_SIZE);
	if (skb) {
		int last = dpriv->tx_dirty%TX_RING_SIZE;
		struct TxFD *tx_fd = dpriv->tx_fd + last;

		skb->len = DUMMY_SKB_SIZE;
		skb_copy_to_linear_data(skb, version,
					strlen(version) % DUMMY_SKB_SIZE);
		tx_fd->state = FrameEnd | TO_STATE_TX(DUMMY_SKB_SIZE);
		tx_fd->data = cpu_to_le32(pci_map_single(dpriv->pci_priv->pdev,
					     skb->data, DUMMY_SKB_SIZE,
					     PCI_DMA_TODEVICE));
		dpriv->tx_skbuff[last] = skb;
	}
	return skb;
}

static int dscc4_init_ring(struct net_device *dev)
{
	struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
	struct pci_dev *pdev = dpriv->pci_priv->pdev;
	struct TxFD *tx_fd;
	struct RxFD *rx_fd;
	void *ring;
	int i;

	ring = pci_alloc_consistent(pdev, RX_TOTAL_SIZE, &dpriv->rx_fd_dma);
	if (!ring)
		goto err_out;
	dpriv->rx_fd = rx_fd = (struct RxFD *) ring;

	ring = pci_alloc_consistent(pdev, TX_TOTAL_SIZE, &dpriv->tx_fd_dma);
	if (!ring)
		goto err_free_dma_rx;
	dpriv->tx_fd = tx_fd = (struct TxFD *) ring;

	memset(dpriv->tx_skbuff, 0, sizeof(struct sk_buff *)*TX_RING_SIZE);
	dpriv->tx_dirty = 0xffffffff;
	i = dpriv->tx_current = 0;
	do {
		tx_fd->state = FrameEnd | TO_STATE_TX(2*DUMMY_SKB_SIZE);
		tx_fd->complete = 0x00000000;
	        /* FIXME: NULL should be ok - to be tried */
	        tx_fd->data = cpu_to_le32(dpriv->tx_fd_dma);
		(tx_fd++)->next = cpu_to_le32(dpriv->tx_fd_dma +
					(++i%TX_RING_SIZE)*sizeof(*tx_fd));
	} while (i < TX_RING_SIZE);

	if (!dscc4_init_dummy_skb(dpriv))
		goto err_free_dma_tx;

	memset(dpriv->rx_skbuff, 0, sizeof(struct sk_buff *)*RX_RING_SIZE);
	i = dpriv->rx_dirty = dpriv->rx_current = 0;
	do {
		/* size set by the host. Multiple of 4 bytes please */
	        rx_fd->state1 = HiDesc;
	        rx_fd->state2 = 0x00000000;
	        rx_fd->end = cpu_to_le32(0xbabeface);
	        rx_fd->state1 |= TO_STATE_RX(HDLC_MAX_MRU);
		// FIXME: return value verifiee mais traitement suspect
		if (try_get_rx_skb(dpriv, dev) >= 0)
			dpriv->rx_dirty++;
		(rx_fd++)->next = cpu_to_le32(dpriv->rx_fd_dma +
					(++i%RX_RING_SIZE)*sizeof(*rx_fd));
	} while (i < RX_RING_SIZE);

	return 0;

err_free_dma_tx:
	pci_free_consistent(pdev, TX_TOTAL_SIZE, ring, dpriv->tx_fd_dma);
err_free_dma_rx:
	pci_free_consistent(pdev, RX_TOTAL_SIZE, rx_fd, dpriv->rx_fd_dma);
err_out:
	return -ENOMEM;
}

static void __devexit dscc4_remove_one(struct pci_dev *pdev)
{
	struct dscc4_pci_priv *ppriv;
	struct dscc4_dev_priv *root;
	void __iomem *ioaddr;
	int i;

	ppriv = pci_get_drvdata(pdev);
	root = ppriv->root;

	ioaddr = root->base_addr;

	dscc4_pci_reset(pdev, ioaddr);

	free_irq(pdev->irq, root);
	pci_free_consistent(pdev, IRQ_RING_SIZE*sizeof(u32), ppriv->iqcfg,
			    ppriv->iqcfg_dma);
	for (i = 0; i < dev_per_card; i++) {
		struct dscc4_dev_priv *dpriv = root + i;

		dscc4_release_ring(dpriv);
		pci_free_consistent(pdev, IRQ_RING_SIZE*sizeof(u32),
				    dpriv->iqrx, dpriv->iqrx_dma);
		pci_free_consistent(pdev, IRQ_RING_SIZE*sizeof(u32),
				    dpriv->iqtx, dpriv->iqtx_dma);
	}

	dscc4_free1(pdev);

	iounmap(ioaddr);

	pci_release_region(pdev, 1);
	pci_release_region(pdev, 0);

	pci_disable_device(pdev);
}

static int dscc4_hdlc_attach(struct net_device *dev, unsigned short encoding,
	unsigned short parity)
{
	struct dscc4_dev_priv *dpriv = dscc4_priv(dev);

	if (encoding != ENCODING_NRZ &&
	    encoding != ENCODING_NRZI &&
	    encoding != ENCODING_FM_MARK &&
	    encoding != ENCODING_FM_SPACE &&
	    encoding != ENCODING_MANCHESTER)
		return -EINVAL;

	if (parity != PARITY_NONE &&
	    parity != PARITY_CRC16_PR0_CCITT &&
	    parity != PARITY_CRC16_PR1_CCITT &&
	    parity != PARITY_CRC32_PR0_CCITT &&
	    parity != PARITY_CRC32_PR1_CCITT)
		return -EINVAL;

        dpriv->encoding = encoding;
        dpriv->parity = parity;
	return 0;
}

#ifndef MODULE
static int __init dscc4_setup(char *str)
{
	int *args[] = { &debug, &quartz, NULL }, **p = args;

	while (*p && (get_option(&str, *p) == 2))
		p++;
	return 1;
}

__setup("dscc4.setup=", dscc4_setup);
#endif

static DEFINE_PCI_DEVICE_TABLE(dscc4_pci_tbl) = {
	{ PCI_VENDOR_ID_SIEMENS, PCI_DEVICE_ID_SIEMENS_DSCC4,
	        PCI_ANY_ID, PCI_ANY_ID, },
	{ 0,}
};
MODULE_DEVICE_TABLE(pci, dscc4_pci_tbl);

static struct pci_driver dscc4_driver = {
	.name		= DRV_NAME,
	.id_table	= dscc4_pci_tbl,
	.probe		= dscc4_init_one,
	.remove		= __devexit_p(dscc4_remove_one),
};

static int __init dscc4_init_module(void)
{
	return pci_register_driver(&dscc4_driver);
}

static void __exit dscc4_cleanup_module(void)
{
	pci_unregister_driver(&dscc4_driver);
}

module_init(dscc4_init_module);
module_exit(dscc4_cleanup_module);