xref: /openbmc/linux/drivers/i2c/busses/i2c-riic.c (revision e6e8c6c2) 
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 slave address + RW bit in every case.
16  *
17  * 2) TIE sends slave 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/of_device.h>
46 #include <linux/platform_device.h>
47 #include <linux/pm_runtime.h>
48 #include <linux/reset.h>
49 
50 #define RIIC_ICCR1	0x00
51 #define RIIC_ICCR2	0x04
52 #define RIIC_ICMR1	0x08
53 #define RIIC_ICMR3	0x10
54 #define RIIC_ICSER	0x18
55 #define RIIC_ICIER	0x1c
56 #define RIIC_ICSR2	0x24
57 #define RIIC_ICBRL	0x34
58 #define RIIC_ICBRH	0x38
59 #define RIIC_ICDRT	0x3c
60 #define RIIC_ICDRR	0x40
61 
62 #define ICCR1_ICE	0x80
63 #define ICCR1_IICRST	0x40
64 #define ICCR1_SOWP	0x10
65 
66 #define ICCR2_BBSY	0x80
67 #define ICCR2_SP	0x08
68 #define ICCR2_RS	0x04
69 #define ICCR2_ST	0x02
70 
71 #define ICMR1_CKS_MASK	0x70
72 #define ICMR1_BCWP	0x08
73 #define ICMR1_CKS(_x)	((((_x) << 4) & ICMR1_CKS_MASK) | ICMR1_BCWP)
74 
75 #define ICMR3_RDRFS	0x20
76 #define ICMR3_ACKWP	0x10
77 #define ICMR3_ACKBT	0x08
78 
79 #define ICIER_TIE	0x80
80 #define ICIER_TEIE	0x40
81 #define ICIER_RIE	0x20
82 #define ICIER_NAKIE	0x10
83 #define ICIER_SPIE	0x08
84 
85 #define ICSR2_NACKF	0x10
86 
87 #define ICBR_RESERVED	0xe0 /* Should be 1 on writes */
88 
89 #define RIIC_INIT_MSG	-1
90 
91 struct riic_dev {
92 	void __iomem *base;
93 	u8 *buf;
94 	struct i2c_msg *msg;
95 	int bytes_left;
96 	int err;
97 	int is_last;
98 	struct completion msg_done;
99 	struct i2c_adapter adapter;
100 	struct clk *clk;
101 };
102 
103 struct riic_irq_desc {
104 	int res_num;
105 	irq_handler_t isr;
106 	char *name;
107 };
108 
109 static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u8 reg)
110 {
111 	writeb((readb(riic->base + reg) & ~clear) | set, riic->base + reg);
112 }
113 
114 static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
115 {
116 	struct riic_dev *riic = i2c_get_adapdata(adap);
117 	unsigned long time_left;
118 	int i;
119 	u8 start_bit;
120 
121 	pm_runtime_get_sync(adap->dev.parent);
122 
123 	if (readb(riic->base + RIIC_ICCR2) & ICCR2_BBSY) {
124 		riic->err = -EBUSY;
125 		goto out;
126 	}
127 
128 	reinit_completion(&riic->msg_done);
129 	riic->err = 0;
130 
131 	writeb(0, riic->base + RIIC_ICSR2);
132 
133 	for (i = 0, start_bit = ICCR2_ST; i < num; i++) {
134 		riic->bytes_left = RIIC_INIT_MSG;
135 		riic->buf = msgs[i].buf;
136 		riic->msg = &msgs[i];
137 		riic->is_last = (i == num - 1);
138 
139 		writeb(ICIER_NAKIE | ICIER_TIE, riic->base + RIIC_ICIER);
140 
141 		writeb(start_bit, riic->base + RIIC_ICCR2);
142 
143 		time_left = wait_for_completion_timeout(&riic->msg_done, riic->adapter.timeout);
144 		if (time_left == 0)
145 			riic->err = -ETIMEDOUT;
146 
147 		if (riic->err)
148 			break;
149 
150 		start_bit = ICCR2_RS;
151 	}
152 
153  out:
154 	pm_runtime_put(adap->dev.parent);
155 
156 	return riic->err ?: num;
157 }
158 
159 static irqreturn_t riic_tdre_isr(int irq, void *data)
160 {
161 	struct riic_dev *riic = data;
162 	u8 val;
163 
164 	if (!riic->bytes_left)
165 		return IRQ_NONE;
166 
167 	if (riic->bytes_left == RIIC_INIT_MSG) {
168 		if (riic->msg->flags & I2C_M_RD)
169 			/* On read, switch over to receive interrupt */
170 			riic_clear_set_bit(riic, ICIER_TIE, ICIER_RIE, RIIC_ICIER);
171 		else
172 			/* On write, initialize length */
173 			riic->bytes_left = riic->msg->len;
174 
175 		val = i2c_8bit_addr_from_msg(riic->msg);
176 	} else {
177 		val = *riic->buf;
178 		riic->buf++;
179 		riic->bytes_left--;
180 	}
181 
182 	/*
183 	 * Switch to transmission ended interrupt when done. Do check here
184 	 * after bytes_left was initialized to support SMBUS_QUICK (new msg has
185 	 * 0 length then)
186 	 */
187 	if (riic->bytes_left == 0)
188 		riic_clear_set_bit(riic, ICIER_TIE, ICIER_TEIE, RIIC_ICIER);
189 
190 	/*
191 	 * This acks the TIE interrupt. We get another TIE immediately if our
192 	 * value could be moved to the shadow shift register right away. So
193 	 * this must be after updates to ICIER (where we want to disable TIE)!
194 	 */
195 	writeb(val, riic->base + RIIC_ICDRT);
196 
197 	return IRQ_HANDLED;
198 }
199 
200 static irqreturn_t riic_tend_isr(int irq, void *data)
201 {
202 	struct riic_dev *riic = data;
203 
204 	if (readb(riic->base + RIIC_ICSR2) & ICSR2_NACKF) {
205 		/* We got a NACKIE */
206 		readb(riic->base + RIIC_ICDRR);	/* dummy read */
207 		riic_clear_set_bit(riic, ICSR2_NACKF, 0, RIIC_ICSR2);
208 		riic->err = -ENXIO;
209 	} else if (riic->bytes_left) {
210 		return IRQ_NONE;
211 	}
212 
213 	if (riic->is_last || riic->err) {
214 		riic_clear_set_bit(riic, ICIER_TEIE, ICIER_SPIE, RIIC_ICIER);
215 		writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
216 	} else {
217 		/* Transfer is complete, but do not send STOP */
218 		riic_clear_set_bit(riic, ICIER_TEIE, 0, RIIC_ICIER);
219 		complete(&riic->msg_done);
220 	}
221 
222 	return IRQ_HANDLED;
223 }
224 
225 static irqreturn_t riic_rdrf_isr(int irq, void *data)
226 {
227 	struct riic_dev *riic = data;
228 
229 	if (!riic->bytes_left)
230 		return IRQ_NONE;
231 
232 	if (riic->bytes_left == RIIC_INIT_MSG) {
233 		riic->bytes_left = riic->msg->len;
234 		readb(riic->base + RIIC_ICDRR);	/* dummy read */
235 		return IRQ_HANDLED;
236 	}
237 
238 	if (riic->bytes_left == 1) {
239 		/* STOP must come before we set ACKBT! */
240 		if (riic->is_last) {
241 			riic_clear_set_bit(riic, 0, ICIER_SPIE, RIIC_ICIER);
242 			writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
243 		}
244 
245 		riic_clear_set_bit(riic, 0, ICMR3_ACKBT, RIIC_ICMR3);
246 
247 	} else {
248 		riic_clear_set_bit(riic, ICMR3_ACKBT, 0, RIIC_ICMR3);
249 	}
250 
251 	/* Reading acks the RIE interrupt */
252 	*riic->buf = readb(riic->base + RIIC_ICDRR);
253 	riic->buf++;
254 	riic->bytes_left--;
255 
256 	return IRQ_HANDLED;
257 }
258 
259 static irqreturn_t riic_stop_isr(int irq, void *data)
260 {
261 	struct riic_dev *riic = data;
262 
263 	/* read back registers to confirm writes have fully propagated */
264 	writeb(0, riic->base + RIIC_ICSR2);
265 	readb(riic->base + RIIC_ICSR2);
266 	writeb(0, riic->base + RIIC_ICIER);
267 	readb(riic->base + RIIC_ICIER);
268 
269 	complete(&riic->msg_done);
270 
271 	return IRQ_HANDLED;
272 }
273 
274 static u32 riic_func(struct i2c_adapter *adap)
275 {
276 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
277 }
278 
279 static const struct i2c_algorithm riic_algo = {
280 	.master_xfer	= riic_xfer,
281 	.functionality	= riic_func,
282 };
283 
284 static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
285 {
286 	int ret = 0;
287 	unsigned long rate;
288 	int total_ticks, cks, brl, brh;
289 
290 	pm_runtime_get_sync(riic->adapter.dev.parent);
291 
292 	if (t->bus_freq_hz > I2C_MAX_FAST_MODE_FREQ) {
293 		dev_err(&riic->adapter.dev,
294 			"unsupported bus speed (%dHz). %d max\n",
295 			t->bus_freq_hz, I2C_MAX_FAST_MODE_FREQ);
296 		ret = -EINVAL;
297 		goto out;
298 	}
299 
300 	rate = clk_get_rate(riic->clk);
301 
302 	/*
303 	 * Assume the default register settings:
304 	 *  FER.SCLE = 1 (SCL sync circuit enabled, adds 2 or 3 cycles)
305 	 *  FER.NFE = 1 (noise circuit enabled)
306 	 *  MR3.NF = 0 (1 cycle of noise filtered out)
307 	 *
308 	 * Freq (CKS=000) = (I2CCLK + tr + tf)/ (BRH + 3 + 1) + (BRL + 3 + 1)
309 	 * Freq (CKS!=000) = (I2CCLK + tr + tf)/ (BRH + 2 + 1) + (BRL + 2 + 1)
310 	 */
311 
312 	/*
313 	 * Determine reference clock rate. We must be able to get the desired
314 	 * frequency with only 62 clock ticks max (31 high, 31 low).
315 	 * Aim for a duty of 60% LOW, 40% HIGH.
316 	 */
317 	total_ticks = DIV_ROUND_UP(rate, t->bus_freq_hz);
318 
319 	for (cks = 0; cks < 7; cks++) {
320 		/*
321 		 * 60% low time must be less than BRL + 2 + 1
322 		 * BRL max register value is 0x1F.
323 		 */
324 		brl = ((total_ticks * 6) / 10);
325 		if (brl <= (0x1F + 3))
326 			break;
327 
328 		total_ticks /= 2;
329 		rate /= 2;
330 	}
331 
332 	if (brl > (0x1F + 3)) {
333 		dev_err(&riic->adapter.dev, "invalid speed (%lu). Too slow.\n",
334 			(unsigned long)t->bus_freq_hz);
335 		ret = -EINVAL;
336 		goto out;
337 	}
338 
339 	brh = total_ticks - brl;
340 
341 	/* Remove automatic clock ticks for sync circuit and NF */
342 	if (cks == 0) {
343 		brl -= 4;
344 		brh -= 4;
345 	} else {
346 		brl -= 3;
347 		brh -= 3;
348 	}
349 
350 	/*
351 	 * Remove clock ticks for rise and fall times. Convert ns to clock
352 	 * ticks.
353 	 */
354 	brl -= t->scl_fall_ns / (1000000000 / rate);
355 	brh -= t->scl_rise_ns / (1000000000 / rate);
356 
357 	/* Adjust for min register values for when SCLE=1 and NFE=1 */
358 	if (brl < 1)
359 		brl = 1;
360 	if (brh < 1)
361 		brh = 1;
362 
363 	pr_debug("i2c-riic: freq=%lu, duty=%d, fall=%lu, rise=%lu, cks=%d, brl=%d, brh=%d\n",
364 		 rate / total_ticks, ((brl + 3) * 100) / (brl + brh + 6),
365 		 t->scl_fall_ns / (1000000000 / rate),
366 		 t->scl_rise_ns / (1000000000 / rate), cks, brl, brh);
367 
368 	/* Changing the order of accessing IICRST and ICE may break things! */
369 	writeb(ICCR1_IICRST | ICCR1_SOWP, riic->base + RIIC_ICCR1);
370 	riic_clear_set_bit(riic, 0, ICCR1_ICE, RIIC_ICCR1);
371 
372 	writeb(ICMR1_CKS(cks), riic->base + RIIC_ICMR1);
373 	writeb(brh | ICBR_RESERVED, riic->base + RIIC_ICBRH);
374 	writeb(brl | ICBR_RESERVED, riic->base + RIIC_ICBRL);
375 
376 	writeb(0, riic->base + RIIC_ICSER);
377 	writeb(ICMR3_ACKWP | ICMR3_RDRFS, riic->base + RIIC_ICMR3);
378 
379 	riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);
380 
381 out:
382 	pm_runtime_put(riic->adapter.dev.parent);
383 	return ret;
384 }
385 
386 static struct riic_irq_desc riic_irqs[] = {
387 	{ .res_num = 0, .isr = riic_tend_isr, .name = "riic-tend" },
388 	{ .res_num = 1, .isr = riic_rdrf_isr, .name = "riic-rdrf" },
389 	{ .res_num = 2, .isr = riic_tdre_isr, .name = "riic-tdre" },
390 	{ .res_num = 3, .isr = riic_stop_isr, .name = "riic-stop" },
391 	{ .res_num = 5, .isr = riic_tend_isr, .name = "riic-nack" },
392 };
393 
394 static void riic_reset_control_assert(void *data)
395 {
396 	reset_control_assert(data);
397 }
398 
399 static int riic_i2c_probe(struct platform_device *pdev)
400 {
401 	struct riic_dev *riic;
402 	struct i2c_adapter *adap;
403 	struct resource *res;
404 	struct i2c_timings i2c_t;
405 	struct reset_control *rstc;
406 	int i, ret;
407 
408 	riic = devm_kzalloc(&pdev->dev, sizeof(*riic), GFP_KERNEL);
409 	if (!riic)
410 		return -ENOMEM;
411 
412 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
413 	riic->base = devm_ioremap_resource(&pdev->dev, res);
414 	if (IS_ERR(riic->base))
415 		return PTR_ERR(riic->base);
416 
417 	riic->clk = devm_clk_get(&pdev->dev, NULL);
418 	if (IS_ERR(riic->clk)) {
419 		dev_err(&pdev->dev, "missing controller clock");
420 		return PTR_ERR(riic->clk);
421 	}
422 
423 	rstc = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
424 	if (IS_ERR(rstc))
425 		return dev_err_probe(&pdev->dev, PTR_ERR(rstc),
426 				     "Error: missing reset ctrl\n");
427 
428 	ret = reset_control_deassert(rstc);
429 	if (ret)
430 		return ret;
431 
432 	ret = devm_add_action_or_reset(&pdev->dev, riic_reset_control_assert, rstc);
433 	if (ret)
434 		return ret;
435 
436 	for (i = 0; i < ARRAY_SIZE(riic_irqs); i++) {
437 		ret = platform_get_irq(pdev, riic_irqs[i].res_num);
438 		if (ret < 0)
439 			return ret;
440 
441 		ret = devm_request_irq(&pdev->dev, ret, riic_irqs[i].isr,
442 				       0, riic_irqs[i].name, riic);
443 		if (ret) {
444 			dev_err(&pdev->dev, "failed to request irq %s\n", riic_irqs[i].name);
445 			return ret;
446 		}
447 	}
448 
449 	adap = &riic->adapter;
450 	i2c_set_adapdata(adap, riic);
451 	strscpy(adap->name, "Renesas RIIC adapter", sizeof(adap->name));
452 	adap->owner = THIS_MODULE;
453 	adap->algo = &riic_algo;
454 	adap->dev.parent = &pdev->dev;
455 	adap->dev.of_node = pdev->dev.of_node;
456 
457 	init_completion(&riic->msg_done);
458 
459 	i2c_parse_fw_timings(&pdev->dev, &i2c_t, true);
460 
461 	pm_runtime_enable(&pdev->dev);
462 
463 	ret = riic_init_hw(riic, &i2c_t);
464 	if (ret)
465 		goto out;
466 
467 	ret = i2c_add_adapter(adap);
468 	if (ret)
469 		goto out;
470 
471 	platform_set_drvdata(pdev, riic);
472 
473 	dev_info(&pdev->dev, "registered with %dHz bus speed\n",
474 		 i2c_t.bus_freq_hz);
475 	return 0;
476 
477 out:
478 	pm_runtime_disable(&pdev->dev);
479 	return ret;
480 }
481 
482 static int riic_i2c_remove(struct platform_device *pdev)
483 {
484 	struct riic_dev *riic = platform_get_drvdata(pdev);
485 
486 	pm_runtime_get_sync(&pdev->dev);
487 	writeb(0, riic->base + RIIC_ICIER);
488 	pm_runtime_put(&pdev->dev);
489 	i2c_del_adapter(&riic->adapter);
490 	pm_runtime_disable(&pdev->dev);
491 
492 	return 0;
493 }
494 
495 static const struct of_device_id riic_i2c_dt_ids[] = {
496 	{ .compatible = "renesas,riic-rz", },
497 	{ /* Sentinel */ },
498 };
499 
500 static struct platform_driver riic_i2c_driver = {
501 	.probe		= riic_i2c_probe,
502 	.remove		= riic_i2c_remove,
503 	.driver		= {
504 		.name	= "i2c-riic",
505 		.of_match_table = riic_i2c_dt_ids,
506 	},
507 };
508 
509 module_platform_driver(riic_i2c_driver);
510 
511 MODULE_DESCRIPTION("Renesas RIIC adapter");
512 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
513 MODULE_LICENSE("GPL v2");
514 MODULE_DEVICE_TABLE(of, riic_i2c_dt_ids);
515