summaryrefslogtreecommitdiffstats
path: root/drivers/i2c/busses/i2c-riic.c
blob: f31413fd9521ef9f2cd60d478c915fe8ae215323 (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
// SPDX-License-Identifier: GPL-2.0
/*
 * Renesas RIIC driver
 *
 * Copyright (C) 2013 Wolfram Sang <wsa@sang-engineering.com>
 * Copyright (C) 2013 Renesas Solutions Corp.
 */

/*
 * This i2c core has a lot of interrupts, namely 8. We use their chaining as
 * some kind of state machine.
 *
 * 1) The main xfer routine kicks off a transmission by putting the start bit
 * (or repeated start) on the bus and enabling the transmit interrupt (TIE)
 * since we need to send the slave address + RW bit in every case.
 *
 * 2) TIE sends slave address + RW bit and selects how to continue.
 *
 * 3a) Write case: We keep utilizing TIE as long as we have data to send. If we
 * are done, we switch over to the transmission done interrupt (TEIE) and mark
 * the message as completed (includes sending STOP) there.
 *
 * 3b) Read case: We switch over to receive interrupt (RIE). One dummy read is
 * needed to start clocking, then we keep receiving until we are done. Note
 * that we use the RDRFS mode all the time, i.e. we ACK/NACK every byte by
 * writing to the ACKBT bit. I tried using the RDRFS mode only at the end of a
 * message to create the final NACK as sketched in the datasheet. This caused
 * some subtle races (when byte n was processed and byte n+1 was already
 * waiting), though, and I started with the safe approach.
 *
 * 4) If we got a NACK somewhere, we flag the error and stop the transmission
 * via NAKIE.
 *
 * Also check the comments in the interrupt routines for some gory details.
 */

#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>

#define RIIC_ICCR1	0x00
#define RIIC_ICCR2	0x04
#define RIIC_ICMR1	0x08
#define RIIC_ICMR3	0x10
#define RIIC_ICSER	0x18
#define RIIC_ICIER	0x1c
#define RIIC_ICSR2	0x24
#define RIIC_ICBRL	0x34
#define RIIC_ICBRH	0x38
#define RIIC_ICDRT	0x3c
#define RIIC_ICDRR	0x40

#define ICCR1_ICE	0x80
#define ICCR1_IICRST	0x40
#define ICCR1_SOWP	0x10

#define ICCR2_BBSY	0x80
#define ICCR2_SP	0x08
#define ICCR2_RS	0x04
#define ICCR2_ST	0x02

#define ICMR1_CKS_MASK	0x70
#define ICMR1_BCWP	0x08
#define ICMR1_CKS(_x)	((((_x) << 4) & ICMR1_CKS_MASK) | ICMR1_BCWP)

#define ICMR3_RDRFS	0x20
#define ICMR3_ACKWP	0x10
#define ICMR3_ACKBT	0x08

#define ICIER_TIE	0x80
#define ICIER_TEIE	0x40
#define ICIER_RIE	0x20
#define ICIER_NAKIE	0x10
#define ICIER_SPIE	0x08

#define ICSR2_NACKF	0x10

#define ICBR_RESERVED	0xe0 /* Should be 1 on writes */

#define RIIC_INIT_MSG	-1

struct riic_dev {
	void __iomem *base;
	u8 *buf;
	struct i2c_msg *msg;
	int bytes_left;
	int err;
	int is_last;
	struct completion msg_done;
	struct i2c_adapter adapter;
	struct clk *clk;
};

struct riic_irq_desc {
	int res_num;
	irq_handler_t isr;
	char *name;
};

static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u8 reg)
{
	writeb((readb(riic->base + reg) & ~clear) | set, riic->base + reg);
}

static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
{
	struct riic_dev *riic = i2c_get_adapdata(adap);
	unsigned long time_left;
	int i;
	u8 start_bit;

	pm_runtime_get_sync(adap->dev.parent);

	if (readb(riic->base + RIIC_ICCR2) & ICCR2_BBSY) {
		riic->err = -EBUSY;
		goto out;
	}

	reinit_completion(&riic->msg_done);
	riic->err = 0;

	writeb(0, riic->base + RIIC_ICSR2);

	for (i = 0, start_bit = ICCR2_ST; i < num; i++) {
		riic->bytes_left = RIIC_INIT_MSG;
		riic->buf = msgs[i].buf;
		riic->msg = &msgs[i];
		riic->is_last = (i == num - 1);

		writeb(ICIER_NAKIE | ICIER_TIE, riic->base + RIIC_ICIER);

		writeb(start_bit, riic->base + RIIC_ICCR2);

		time_left = wait_for_completion_timeout(&riic->msg_done, riic->adapter.timeout);
		if (time_left == 0)
			riic->err = -ETIMEDOUT;

		if (riic->err)
			break;

		start_bit = ICCR2_RS;
	}

 out:
	pm_runtime_put(adap->dev.parent);

	return riic->err ?: num;
}

static irqreturn_t riic_tdre_isr(int irq, void *data)
{
	struct riic_dev *riic = data;
	u8 val;

	if (!riic->bytes_left)
		return IRQ_NONE;

	if (riic->bytes_left == RIIC_INIT_MSG) {
		if (riic->msg->flags & I2C_M_RD)
			/* On read, switch over to receive interrupt */
			riic_clear_set_bit(riic, ICIER_TIE, ICIER_RIE, RIIC_ICIER);
		else
			/* On write, initialize length */
			riic->bytes_left = riic->msg->len;

		val = i2c_8bit_addr_from_msg(riic->msg);
	} else {
		val = *riic->buf;
		riic->buf++;
		riic->bytes_left--;
	}

	/*
	 * Switch to transmission ended interrupt when done. Do check here
	 * after bytes_left was initialized to support SMBUS_QUICK (new msg has
	 * 0 length then)
	 */
	if (riic->bytes_left == 0)
		riic_clear_set_bit(riic, ICIER_TIE, ICIER_TEIE, RIIC_ICIER);

	/*
	 * This acks the TIE interrupt. We get another TIE immediately if our
	 * value could be moved to the shadow shift register right away. So
	 * this must be after updates to ICIER (where we want to disable TIE)!
	 */
	writeb(val, riic->base + RIIC_ICDRT);

	return IRQ_HANDLED;
}

static irqreturn_t riic_tend_isr(int irq, void *data)
{
	struct riic_dev *riic = data;

	if (readb(riic->base + RIIC_ICSR2) & ICSR2_NACKF) {
		/* We got a NACKIE */
		readb(riic->base + RIIC_ICDRR);	/* dummy read */
		riic->err = -ENXIO;
	} else if (riic->bytes_left) {
		return IRQ_NONE;
	}

	if (riic->is_last || riic->err) {
		riic_clear_set_bit(riic, ICIER_TEIE, ICIER_SPIE, RIIC_ICIER);
		writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
	} else {
		/* Transfer is complete, but do not send STOP */
		riic_clear_set_bit(riic, ICIER_TEIE, 0, RIIC_ICIER);
		complete(&riic->msg_done);
	}

	return IRQ_HANDLED;
}

static irqreturn_t riic_rdrf_isr(int irq, void *data)
{
	struct riic_dev *riic = data;

	if (!riic->bytes_left)
		return IRQ_NONE;

	if (riic->bytes_left == RIIC_INIT_MSG) {
		riic->bytes_left = riic->msg->len;
		readb(riic->base + RIIC_ICDRR);	/* dummy read */
		return IRQ_HANDLED;
	}

	if (riic->bytes_left == 1) {
		/* STOP must come before we set ACKBT! */
		if (riic->is_last) {
			riic_clear_set_bit(riic, 0, ICIER_SPIE, RIIC_ICIER);
			writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
		}

		riic_clear_set_bit(riic, 0, ICMR3_ACKBT, RIIC_ICMR3);

	} else {
		riic_clear_set_bit(riic, ICMR3_ACKBT, 0, RIIC_ICMR3);
	}

	/* Reading acks the RIE interrupt */
	*riic->buf = readb(riic->base + RIIC_ICDRR);
	riic->buf++;
	riic->bytes_left--;

	return IRQ_HANDLED;
}

static irqreturn_t riic_stop_isr(int irq, void *data)
{
	struct riic_dev *riic = data;

	/* read back registers to confirm writes have fully propagated */
	writeb(0, riic->base + RIIC_ICSR2);
	readb(riic->base + RIIC_ICSR2);
	writeb(0, riic->base + RIIC_ICIER);
	readb(riic->base + RIIC_ICIER);

	complete(&riic->msg_done);

	return IRQ_HANDLED;
}

static u32 riic_func(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static const struct i2c_algorithm riic_algo = {
	.master_xfer	= riic_xfer,
	.functionality	= riic_func,
};

static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
{
	int ret = 0;
	unsigned long rate;
	int total_ticks, cks, brl, brh;

	pm_runtime_get_sync(riic->adapter.dev.parent);

	if (t->bus_freq_hz > 400000) {
		dev_err(&riic->adapter.dev,
			"unsupported bus speed (%dHz). 400000 max\n",
			t->bus_freq_hz);
		ret = -EINVAL;
		goto out;
	}

	rate = clk_get_rate(riic->clk);

	/*
	 * Assume the default register settings:
	 *  FER.SCLE = 1 (SCL sync circuit enabled, adds 2 or 3 cycles)
	 *  FER.NFE = 1 (noise circuit enabled)
	 *  MR3.NF = 0 (1 cycle of noise filtered out)
	 *
	 * Freq (CKS=000) = (I2CCLK + tr + tf)/ (BRH + 3 + 1) + (BRL + 3 + 1)
	 * Freq (CKS!=000) = (I2CCLK + tr + tf)/ (BRH + 2 + 1) + (BRL + 2 + 1)
	 */

	/*
	 * Determine reference clock rate. We must be able to get the desired
	 * frequency with only 62 clock ticks max (31 high, 31 low).
	 * Aim for a duty of 60% LOW, 40% HIGH.
	 */
	total_ticks = DIV_ROUND_UP(rate, t->bus_freq_hz);

	for (cks = 0; cks < 7; cks++) {
		/*
		 * 60% low time must be less than BRL + 2 + 1
		 * BRL max register value is 0x1F.
		 */
		brl = ((total_ticks * 6) / 10);
		if (brl <= (0x1F + 3))
			break;

		total_ticks /= 2;
		rate /= 2;
	}

	if (brl > (0x1F + 3)) {
		dev_err(&riic->adapter.dev, "invalid speed (%lu). Too slow.\n",
			(unsigned long)t->bus_freq_hz);
		ret = -EINVAL;
		goto out;
	}

	brh = total_ticks - brl;

	/* Remove automatic clock ticks for sync circuit and NF */
	if (cks == 0) {
		brl -= 4;
		brh -= 4;
	} else {
		brl -= 3;
		brh -= 3;
	}

	/*
	 * Remove clock ticks for rise and fall times. Convert ns to clock
	 * ticks.
	 */
	brl -= t->scl_fall_ns / (1000000000 / rate);
	brh -= t->scl_rise_ns / (1000000000 / rate);

	/* Adjust for min register values for when SCLE=1 and NFE=1 */
	if (brl < 1)
		brl = 1;
	if (brh < 1)
		brh = 1;

	pr_debug("i2c-riic: freq=%lu, duty=%d, fall=%lu, rise=%lu, cks=%d, brl=%d, brh=%d\n",
		 rate / total_ticks, ((brl + 3) * 100) / (brl + brh + 6),
		 t->scl_fall_ns / (1000000000 / rate),
		 t->scl_rise_ns / (1000000000 / rate), cks, brl, brh);

	/* Changing the order of accessing IICRST and ICE may break things! */
	writeb(ICCR1_IICRST | ICCR1_SOWP, riic->base + RIIC_ICCR1);
	riic_clear_set_bit(riic, 0, ICCR1_ICE, RIIC_ICCR1);

	writeb(ICMR1_CKS(cks), riic->base + RIIC_ICMR1);
	writeb(brh | ICBR_RESERVED, riic->base + RIIC_ICBRH);
	writeb(brl | ICBR_RESERVED, riic->base + RIIC_ICBRL);

	writeb(0, riic->base + RIIC_ICSER);
	writeb(ICMR3_ACKWP | ICMR3_RDRFS, riic->base + RIIC_ICMR3);

	riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);

out:
	pm_runtime_put(riic->adapter.dev.parent);
	return ret;
}

static struct riic_irq_desc riic_irqs[] = {
	{ .res_num = 0, .isr = riic_tend_isr, .name = "riic-tend" },
	{ .res_num = 1, .isr = riic_rdrf_isr, .name = "riic-rdrf" },
	{ .res_num = 2, .isr = riic_tdre_isr, .name = "riic-tdre" },
	{ .res_num = 3, .isr = riic_stop_isr, .name = "riic-stop" },
	{ .res_num = 5, .isr = riic_tend_isr, .name = "riic-nack" },
};

static int riic_i2c_probe(struct platform_device *pdev)
{
	struct riic_dev *riic;
	struct i2c_adapter *adap;
	struct resource *res;
	struct i2c_timings i2c_t;
	int i, ret;

	riic = devm_kzalloc(&pdev->dev, sizeof(*riic), GFP_KERNEL);
	if (!riic)
		return -ENOMEM;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	riic->base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(riic->base))
		return PTR_ERR(riic->base);

	riic->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(riic->clk)) {
		dev_err(&pdev->dev, "missing controller clock");
		return PTR_ERR(riic->clk);
	}

	for (i = 0; i < ARRAY_SIZE(riic_irqs); i++) {
		res = platform_get_resource(pdev, IORESOURCE_IRQ, riic_irqs[i].res_num);
		if (!res)
			return -ENODEV;

		ret = devm_request_irq(&pdev->dev, res->start, riic_irqs[i].isr,
					0, riic_irqs[i].name, riic);
		if (ret) {
			dev_err(&pdev->dev, "failed to request irq %s\n", riic_irqs[i].name);
			return ret;
		}
	}

	adap = &riic->adapter;
	i2c_set_adapdata(adap, riic);
	strlcpy(adap->name, "Renesas RIIC adapter", sizeof(adap->name));
	adap->owner = THIS_MODULE;
	adap->algo = &riic_algo;
	adap->dev.parent = &pdev->dev;
	adap->dev.of_node = pdev->dev.of_node;

	init_completion(&riic->msg_done);

	i2c_parse_fw_timings(&pdev->dev, &i2c_t, true);

	pm_runtime_enable(&pdev->dev);

	ret = riic_init_hw(riic, &i2c_t);
	if (ret)
		goto out;

	ret = i2c_add_adapter(adap);
	if (ret)
		goto out;

	platform_set_drvdata(pdev, riic);

	dev_info(&pdev->dev, "registered with %dHz bus speed\n",
		 i2c_t.bus_freq_hz);
	return 0;

out:
	pm_runtime_disable(&pdev->dev);
	return ret;
}

static int riic_i2c_remove(struct platform_device *pdev)
{
	struct riic_dev *riic = platform_get_drvdata(pdev);

	pm_runtime_get_sync(&pdev->dev);
	writeb(0, riic->base + RIIC_ICIER);
	pm_runtime_put(&pdev->dev);
	i2c_del_adapter(&riic->adapter);
	pm_runtime_disable(&pdev->dev);

	return 0;
}

static const struct of_device_id riic_i2c_dt_ids[] = {
	{ .compatible = "renesas,riic-rz" },
	{ /* Sentinel */ },
};

static struct platform_driver riic_i2c_driver = {
	.probe		= riic_i2c_probe,
	.remove		= riic_i2c_remove,
	.driver		= {
		.name	= "i2c-riic",
		.of_match_table = riic_i2c_dt_ids,
	},
};

module_platform_driver(riic_i2c_driver);

MODULE_DESCRIPTION("Renesas RIIC adapter");
MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
MODULE_LICENSE("GPL v2");
MODULE_DEVICE_TABLE(of, riic_i2c_dt_ids);