xref: /linux/drivers/i2c/busses/i2c-riic.c (revision 4b132aacb0768ac1e652cf517097ea6f237214b9) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Renesas RIIC driver
4  *
5  * Copyright (C) 2013 Wolfram Sang <wsa@sang-engineering.com>
6  * Copyright (C) 2013 Renesas Solutions Corp.
7  */
8 
9 /*
10  * This i2c core has a lot of interrupts, namely 8. We use their chaining as
11  * some kind of state machine.
12  *
13  * 1) The main xfer routine kicks off a transmission by putting the start bit
14  * (or repeated start) on the bus and enabling the transmit interrupt (TIE)
15  * since we need to send the target address + RW bit in every case.
16  *
17  * 2) TIE sends target address + RW bit and selects how to continue.
18  *
19  * 3a) Write case: We keep utilizing TIE as long as we have data to send. If we
20  * are done, we switch over to the transmission done interrupt (TEIE) and mark
21  * the message as completed (includes sending STOP) there.
22  *
23  * 3b) Read case: We switch over to receive interrupt (RIE). One dummy read is
24  * needed to start clocking, then we keep receiving until we are done. Note
25  * that we use the RDRFS mode all the time, i.e. we ACK/NACK every byte by
26  * writing to the ACKBT bit. I tried using the RDRFS mode only at the end of a
27  * message to create the final NACK as sketched in the datasheet. This caused
28  * some subtle races (when byte n was processed and byte n+1 was already
29  * waiting), though, and I started with the safe approach.
30  *
31  * 4) If we got a NACK somewhere, we flag the error and stop the transmission
32  * via NAKIE.
33  *
34  * Also check the comments in the interrupt routines for some gory details.
35  */
36 
37 #include <linux/clk.h>
38 #include <linux/completion.h>
39 #include <linux/err.h>
40 #include <linux/i2c.h>
41 #include <linux/interrupt.h>
42 #include <linux/io.h>
43 #include <linux/module.h>
44 #include <linux/of.h>
45 #include <linux/platform_device.h>
46 #include <linux/pm_runtime.h>
47 #include <linux/reset.h>
48 
49 #define ICCR1_ICE	0x80
50 #define ICCR1_IICRST	0x40
51 #define ICCR1_SOWP	0x10
52 
53 #define ICCR2_BBSY	0x80
54 #define ICCR2_SP	0x08
55 #define ICCR2_RS	0x04
56 #define ICCR2_ST	0x02
57 
58 #define ICMR1_CKS_MASK	0x70
59 #define ICMR1_BCWP	0x08
60 #define ICMR1_CKS(_x)	((((_x) << 4) & ICMR1_CKS_MASK) | ICMR1_BCWP)
61 
62 #define ICMR3_RDRFS	0x20
63 #define ICMR3_ACKWP	0x10
64 #define ICMR3_ACKBT	0x08
65 
66 #define ICIER_TIE	0x80
67 #define ICIER_TEIE	0x40
68 #define ICIER_RIE	0x20
69 #define ICIER_NAKIE	0x10
70 #define ICIER_SPIE	0x08
71 
72 #define ICSR2_NACKF	0x10
73 
74 #define ICBR_RESERVED	0xe0 /* Should be 1 on writes */
75 
76 #define RIIC_INIT_MSG	-1
77 
78 enum riic_reg_list {
79 	RIIC_ICCR1 = 0,
80 	RIIC_ICCR2,
81 	RIIC_ICMR1,
82 	RIIC_ICMR3,
83 	RIIC_ICSER,
84 	RIIC_ICIER,
85 	RIIC_ICSR2,
86 	RIIC_ICBRL,
87 	RIIC_ICBRH,
88 	RIIC_ICDRT,
89 	RIIC_ICDRR,
90 	RIIC_REG_END,
91 };
92 
93 struct riic_of_data {
94 	u8 regs[RIIC_REG_END];
95 };
96 
97 struct riic_dev {
98 	void __iomem *base;
99 	u8 *buf;
100 	struct i2c_msg *msg;
101 	int bytes_left;
102 	int err;
103 	int is_last;
104 	const struct riic_of_data *info;
105 	struct completion msg_done;
106 	struct i2c_adapter adapter;
107 	struct clk *clk;
108 };
109 
110 struct riic_irq_desc {
111 	int res_num;
112 	irq_handler_t isr;
113 	char *name;
114 };
115 
116 static inline void riic_writeb(struct riic_dev *riic, u8 val, u8 offset)
117 {
118 	writeb(val, riic->base + riic->info->regs[offset]);
119 }
120 
121 static inline u8 riic_readb(struct riic_dev *riic, u8 offset)
122 {
123 	return readb(riic->base + riic->info->regs[offset]);
124 }
125 
126 static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u8 reg)
127 {
128 	riic_writeb(riic, (riic_readb(riic, reg) & ~clear) | set, reg);
129 }
130 
131 static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
132 {
133 	struct riic_dev *riic = i2c_get_adapdata(adap);
134 	unsigned long time_left;
135 	int i;
136 	u8 start_bit;
137 
138 	pm_runtime_get_sync(adap->dev.parent);
139 
140 	if (riic_readb(riic, RIIC_ICCR2) & ICCR2_BBSY) {
141 		riic->err = -EBUSY;
142 		goto out;
143 	}
144 
145 	reinit_completion(&riic->msg_done);
146 	riic->err = 0;
147 
148 	riic_writeb(riic, 0, RIIC_ICSR2);
149 
150 	for (i = 0, start_bit = ICCR2_ST; i < num; i++) {
151 		riic->bytes_left = RIIC_INIT_MSG;
152 		riic->buf = msgs[i].buf;
153 		riic->msg = &msgs[i];
154 		riic->is_last = (i == num - 1);
155 
156 		riic_writeb(riic, ICIER_NAKIE | ICIER_TIE, RIIC_ICIER);
157 
158 		riic_writeb(riic, start_bit, RIIC_ICCR2);
159 
160 		time_left = wait_for_completion_timeout(&riic->msg_done, riic->adapter.timeout);
161 		if (time_left == 0)
162 			riic->err = -ETIMEDOUT;
163 
164 		if (riic->err)
165 			break;
166 
167 		start_bit = ICCR2_RS;
168 	}
169 
170  out:
171 	pm_runtime_put(adap->dev.parent);
172 
173 	return riic->err ?: num;
174 }
175 
176 static irqreturn_t riic_tdre_isr(int irq, void *data)
177 {
178 	struct riic_dev *riic = data;
179 	u8 val;
180 
181 	if (!riic->bytes_left)
182 		return IRQ_NONE;
183 
184 	if (riic->bytes_left == RIIC_INIT_MSG) {
185 		if (riic->msg->flags & I2C_M_RD)
186 			/* On read, switch over to receive interrupt */
187 			riic_clear_set_bit(riic, ICIER_TIE, ICIER_RIE, RIIC_ICIER);
188 		else
189 			/* On write, initialize length */
190 			riic->bytes_left = riic->msg->len;
191 
192 		val = i2c_8bit_addr_from_msg(riic->msg);
193 	} else {
194 		val = *riic->buf;
195 		riic->buf++;
196 		riic->bytes_left--;
197 	}
198 
199 	/*
200 	 * Switch to transmission ended interrupt when done. Do check here
201 	 * after bytes_left was initialized to support SMBUS_QUICK (new msg has
202 	 * 0 length then)
203 	 */
204 	if (riic->bytes_left == 0)
205 		riic_clear_set_bit(riic, ICIER_TIE, ICIER_TEIE, RIIC_ICIER);
206 
207 	/*
208 	 * This acks the TIE interrupt. We get another TIE immediately if our
209 	 * value could be moved to the shadow shift register right away. So
210 	 * this must be after updates to ICIER (where we want to disable TIE)!
211 	 */
212 	riic_writeb(riic, val, RIIC_ICDRT);
213 
214 	return IRQ_HANDLED;
215 }
216 
217 static irqreturn_t riic_tend_isr(int irq, void *data)
218 {
219 	struct riic_dev *riic = data;
220 
221 	if (riic_readb(riic, RIIC_ICSR2) & ICSR2_NACKF) {
222 		/* We got a NACKIE */
223 		riic_readb(riic, RIIC_ICDRR);	/* dummy read */
224 		riic_clear_set_bit(riic, ICSR2_NACKF, 0, RIIC_ICSR2);
225 		riic->err = -ENXIO;
226 	} else if (riic->bytes_left) {
227 		return IRQ_NONE;
228 	}
229 
230 	if (riic->is_last || riic->err) {
231 		riic_clear_set_bit(riic, ICIER_TEIE, ICIER_SPIE, RIIC_ICIER);
232 		riic_writeb(riic, ICCR2_SP, RIIC_ICCR2);
233 	} else {
234 		/* Transfer is complete, but do not send STOP */
235 		riic_clear_set_bit(riic, ICIER_TEIE, 0, RIIC_ICIER);
236 		complete(&riic->msg_done);
237 	}
238 
239 	return IRQ_HANDLED;
240 }
241 
242 static irqreturn_t riic_rdrf_isr(int irq, void *data)
243 {
244 	struct riic_dev *riic = data;
245 
246 	if (!riic->bytes_left)
247 		return IRQ_NONE;
248 
249 	if (riic->bytes_left == RIIC_INIT_MSG) {
250 		riic->bytes_left = riic->msg->len;
251 		riic_readb(riic, RIIC_ICDRR);	/* dummy read */
252 		return IRQ_HANDLED;
253 	}
254 
255 	if (riic->bytes_left == 1) {
256 		/* STOP must come before we set ACKBT! */
257 		if (riic->is_last) {
258 			riic_clear_set_bit(riic, 0, ICIER_SPIE, RIIC_ICIER);
259 			riic_writeb(riic, ICCR2_SP, RIIC_ICCR2);
260 		}
261 
262 		riic_clear_set_bit(riic, 0, ICMR3_ACKBT, RIIC_ICMR3);
263 
264 	} else {
265 		riic_clear_set_bit(riic, ICMR3_ACKBT, 0, RIIC_ICMR3);
266 	}
267 
268 	/* Reading acks the RIE interrupt */
269 	*riic->buf = riic_readb(riic, RIIC_ICDRR);
270 	riic->buf++;
271 	riic->bytes_left--;
272 
273 	return IRQ_HANDLED;
274 }
275 
276 static irqreturn_t riic_stop_isr(int irq, void *data)
277 {
278 	struct riic_dev *riic = data;
279 
280 	/* read back registers to confirm writes have fully propagated */
281 	riic_writeb(riic, 0, RIIC_ICSR2);
282 	riic_readb(riic, RIIC_ICSR2);
283 	riic_writeb(riic, 0, RIIC_ICIER);
284 	riic_readb(riic, RIIC_ICIER);
285 
286 	complete(&riic->msg_done);
287 
288 	return IRQ_HANDLED;
289 }
290 
291 static u32 riic_func(struct i2c_adapter *adap)
292 {
293 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
294 }
295 
296 static const struct i2c_algorithm riic_algo = {
297 	.xfer = riic_xfer,
298 	.functionality = riic_func,
299 };
300 
301 static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
302 {
303 	int ret = 0;
304 	unsigned long rate;
305 	int total_ticks, cks, brl, brh;
306 
307 	pm_runtime_get_sync(riic->adapter.dev.parent);
308 
309 	if (t->bus_freq_hz > I2C_MAX_FAST_MODE_FREQ) {
310 		dev_err(&riic->adapter.dev,
311 			"unsupported bus speed (%dHz). %d max\n",
312 			t->bus_freq_hz, I2C_MAX_FAST_MODE_FREQ);
313 		ret = -EINVAL;
314 		goto out;
315 	}
316 
317 	rate = clk_get_rate(riic->clk);
318 
319 	/*
320 	 * Assume the default register settings:
321 	 *  FER.SCLE = 1 (SCL sync circuit enabled, adds 2 or 3 cycles)
322 	 *  FER.NFE = 1 (noise circuit enabled)
323 	 *  MR3.NF = 0 (1 cycle of noise filtered out)
324 	 *
325 	 * Freq (CKS=000) = (I2CCLK + tr + tf)/ (BRH + 3 + 1) + (BRL + 3 + 1)
326 	 * Freq (CKS!=000) = (I2CCLK + tr + tf)/ (BRH + 2 + 1) + (BRL + 2 + 1)
327 	 */
328 
329 	/*
330 	 * Determine reference clock rate. We must be able to get the desired
331 	 * frequency with only 62 clock ticks max (31 high, 31 low).
332 	 * Aim for a duty of 60% LOW, 40% HIGH.
333 	 */
334 	total_ticks = DIV_ROUND_UP(rate, t->bus_freq_hz ?: 1);
335 
336 	for (cks = 0; cks < 7; cks++) {
337 		/*
338 		 * 60% low time must be less than BRL + 2 + 1
339 		 * BRL max register value is 0x1F.
340 		 */
341 		brl = ((total_ticks * 6) / 10);
342 		if (brl <= (0x1F + 3))
343 			break;
344 
345 		total_ticks /= 2;
346 		rate /= 2;
347 	}
348 
349 	if (brl > (0x1F + 3)) {
350 		dev_err(&riic->adapter.dev, "invalid speed (%lu). Too slow.\n",
351 			(unsigned long)t->bus_freq_hz);
352 		ret = -EINVAL;
353 		goto out;
354 	}
355 
356 	brh = total_ticks - brl;
357 
358 	/* Remove automatic clock ticks for sync circuit and NF */
359 	if (cks == 0) {
360 		brl -= 4;
361 		brh -= 4;
362 	} else {
363 		brl -= 3;
364 		brh -= 3;
365 	}
366 
367 	/*
368 	 * Remove clock ticks for rise and fall times. Convert ns to clock
369 	 * ticks.
370 	 */
371 	brl -= t->scl_fall_ns / (1000000000 / rate);
372 	brh -= t->scl_rise_ns / (1000000000 / rate);
373 
374 	/* Adjust for min register values for when SCLE=1 and NFE=1 */
375 	if (brl < 1)
376 		brl = 1;
377 	if (brh < 1)
378 		brh = 1;
379 
380 	pr_debug("i2c-riic: freq=%lu, duty=%d, fall=%lu, rise=%lu, cks=%d, brl=%d, brh=%d\n",
381 		 rate / total_ticks, ((brl + 3) * 100) / (brl + brh + 6),
382 		 t->scl_fall_ns / (1000000000 / rate),
383 		 t->scl_rise_ns / (1000000000 / rate), cks, brl, brh);
384 
385 	/* Changing the order of accessing IICRST and ICE may break things! */
386 	riic_writeb(riic, ICCR1_IICRST | ICCR1_SOWP, RIIC_ICCR1);
387 	riic_clear_set_bit(riic, 0, ICCR1_ICE, RIIC_ICCR1);
388 
389 	riic_writeb(riic, ICMR1_CKS(cks), RIIC_ICMR1);
390 	riic_writeb(riic, brh | ICBR_RESERVED, RIIC_ICBRH);
391 	riic_writeb(riic, brl | ICBR_RESERVED, RIIC_ICBRL);
392 
393 	riic_writeb(riic, 0, RIIC_ICSER);
394 	riic_writeb(riic, ICMR3_ACKWP | ICMR3_RDRFS, RIIC_ICMR3);
395 
396 	riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);
397 
398 out:
399 	pm_runtime_put(riic->adapter.dev.parent);
400 	return ret;
401 }
402 
403 static struct riic_irq_desc riic_irqs[] = {
404 	{ .res_num = 0, .isr = riic_tend_isr, .name = "riic-tend" },
405 	{ .res_num = 1, .isr = riic_rdrf_isr, .name = "riic-rdrf" },
406 	{ .res_num = 2, .isr = riic_tdre_isr, .name = "riic-tdre" },
407 	{ .res_num = 3, .isr = riic_stop_isr, .name = "riic-stop" },
408 	{ .res_num = 5, .isr = riic_tend_isr, .name = "riic-nack" },
409 };
410 
411 static void riic_reset_control_assert(void *data)
412 {
413 	reset_control_assert(data);
414 }
415 
416 static int riic_i2c_probe(struct platform_device *pdev)
417 {
418 	struct riic_dev *riic;
419 	struct i2c_adapter *adap;
420 	struct i2c_timings i2c_t;
421 	struct reset_control *rstc;
422 	int i, ret;
423 
424 	riic = devm_kzalloc(&pdev->dev, sizeof(*riic), GFP_KERNEL);
425 	if (!riic)
426 		return -ENOMEM;
427 
428 	riic->base = devm_platform_ioremap_resource(pdev, 0);
429 	if (IS_ERR(riic->base))
430 		return PTR_ERR(riic->base);
431 
432 	riic->clk = devm_clk_get(&pdev->dev, NULL);
433 	if (IS_ERR(riic->clk)) {
434 		dev_err(&pdev->dev, "missing controller clock");
435 		return PTR_ERR(riic->clk);
436 	}
437 
438 	rstc = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
439 	if (IS_ERR(rstc))
440 		return dev_err_probe(&pdev->dev, PTR_ERR(rstc),
441 				     "Error: missing reset ctrl\n");
442 
443 	ret = reset_control_deassert(rstc);
444 	if (ret)
445 		return ret;
446 
447 	ret = devm_add_action_or_reset(&pdev->dev, riic_reset_control_assert, rstc);
448 	if (ret)
449 		return ret;
450 
451 	for (i = 0; i < ARRAY_SIZE(riic_irqs); i++) {
452 		ret = platform_get_irq(pdev, riic_irqs[i].res_num);
453 		if (ret < 0)
454 			return ret;
455 
456 		ret = devm_request_irq(&pdev->dev, ret, riic_irqs[i].isr,
457 				       0, riic_irqs[i].name, riic);
458 		if (ret) {
459 			dev_err(&pdev->dev, "failed to request irq %s\n", riic_irqs[i].name);
460 			return ret;
461 		}
462 	}
463 
464 	riic->info = of_device_get_match_data(&pdev->dev);
465 
466 	adap = &riic->adapter;
467 	i2c_set_adapdata(adap, riic);
468 	strscpy(adap->name, "Renesas RIIC adapter", sizeof(adap->name));
469 	adap->owner = THIS_MODULE;
470 	adap->algo = &riic_algo;
471 	adap->dev.parent = &pdev->dev;
472 	adap->dev.of_node = pdev->dev.of_node;
473 
474 	init_completion(&riic->msg_done);
475 
476 	i2c_parse_fw_timings(&pdev->dev, &i2c_t, true);
477 
478 	pm_runtime_enable(&pdev->dev);
479 
480 	ret = riic_init_hw(riic, &i2c_t);
481 	if (ret)
482 		goto out;
483 
484 	ret = i2c_add_adapter(adap);
485 	if (ret)
486 		goto out;
487 
488 	platform_set_drvdata(pdev, riic);
489 
490 	dev_info(&pdev->dev, "registered with %dHz bus speed\n",
491 		 i2c_t.bus_freq_hz);
492 	return 0;
493 
494 out:
495 	pm_runtime_disable(&pdev->dev);
496 	return ret;
497 }
498 
499 static void riic_i2c_remove(struct platform_device *pdev)
500 {
501 	struct riic_dev *riic = platform_get_drvdata(pdev);
502 
503 	pm_runtime_get_sync(&pdev->dev);
504 	riic_writeb(riic, 0, RIIC_ICIER);
505 	pm_runtime_put(&pdev->dev);
506 	i2c_del_adapter(&riic->adapter);
507 	pm_runtime_disable(&pdev->dev);
508 }
509 
510 static const struct riic_of_data riic_rz_a_info = {
511 	.regs = {
512 		[RIIC_ICCR1] = 0x00,
513 		[RIIC_ICCR2] = 0x04,
514 		[RIIC_ICMR1] = 0x08,
515 		[RIIC_ICMR3] = 0x10,
516 		[RIIC_ICSER] = 0x18,
517 		[RIIC_ICIER] = 0x1c,
518 		[RIIC_ICSR2] = 0x24,
519 		[RIIC_ICBRL] = 0x34,
520 		[RIIC_ICBRH] = 0x38,
521 		[RIIC_ICDRT] = 0x3c,
522 		[RIIC_ICDRR] = 0x40,
523 	},
524 };
525 
526 static const struct riic_of_data riic_rz_v2h_info = {
527 	.regs = {
528 		[RIIC_ICCR1] = 0x00,
529 		[RIIC_ICCR2] = 0x01,
530 		[RIIC_ICMR1] = 0x02,
531 		[RIIC_ICMR3] = 0x04,
532 		[RIIC_ICSER] = 0x06,
533 		[RIIC_ICIER] = 0x07,
534 		[RIIC_ICSR2] = 0x09,
535 		[RIIC_ICBRL] = 0x10,
536 		[RIIC_ICBRH] = 0x11,
537 		[RIIC_ICDRT] = 0x12,
538 		[RIIC_ICDRR] = 0x13,
539 	},
540 };
541 
542 static const struct of_device_id riic_i2c_dt_ids[] = {
543 	{ .compatible = "renesas,riic-rz", .data = &riic_rz_a_info },
544 	{ .compatible = "renesas,riic-r9a09g057", .data = &riic_rz_v2h_info },
545 	{ /* Sentinel */ },
546 };
547 
548 static struct platform_driver riic_i2c_driver = {
549 	.probe		= riic_i2c_probe,
550 	.remove_new	= riic_i2c_remove,
551 	.driver		= {
552 		.name	= "i2c-riic",
553 		.of_match_table = riic_i2c_dt_ids,
554 	},
555 };
556 
557 module_platform_driver(riic_i2c_driver);
558 
559 MODULE_DESCRIPTION("Renesas RIIC adapter");
560 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
561 MODULE_LICENSE("GPL v2");
562 MODULE_DEVICE_TABLE(of, riic_i2c_dt_ids);
563