xref: /openbmc/linux/drivers/i2c/busses/i2c-riic.c (revision be58f710) 
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 enum riic_type {
92 	RIIC_RZ_A,
93 	RIIC_RZ_G2L,
94 };
95 
96 struct riic_dev {
97 	void __iomem *base;
98 	u8 *buf;
99 	struct i2c_msg *msg;
100 	int bytes_left;
101 	int err;
102 	int is_last;
103 	struct completion msg_done;
104 	struct i2c_adapter adapter;
105 	struct clk *clk;
106 };
107 
108 struct riic_irq_desc {
109 	int res_num;
110 	irq_handler_t isr;
111 	char *name;
112 };
113 
114 static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u8 reg)
115 {
116 	writeb((readb(riic->base + reg) & ~clear) | set, riic->base + reg);
117 }
118 
119 static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
120 {
121 	struct riic_dev *riic = i2c_get_adapdata(adap);
122 	unsigned long time_left;
123 	int i;
124 	u8 start_bit;
125 
126 	pm_runtime_get_sync(adap->dev.parent);
127 
128 	if (readb(riic->base + RIIC_ICCR2) & ICCR2_BBSY) {
129 		riic->err = -EBUSY;
130 		goto out;
131 	}
132 
133 	reinit_completion(&riic->msg_done);
134 	riic->err = 0;
135 
136 	writeb(0, riic->base + RIIC_ICSR2);
137 
138 	for (i = 0, start_bit = ICCR2_ST; i < num; i++) {
139 		riic->bytes_left = RIIC_INIT_MSG;
140 		riic->buf = msgs[i].buf;
141 		riic->msg = &msgs[i];
142 		riic->is_last = (i == num - 1);
143 
144 		writeb(ICIER_NAKIE | ICIER_TIE, riic->base + RIIC_ICIER);
145 
146 		writeb(start_bit, riic->base + RIIC_ICCR2);
147 
148 		time_left = wait_for_completion_timeout(&riic->msg_done, riic->adapter.timeout);
149 		if (time_left == 0)
150 			riic->err = -ETIMEDOUT;
151 
152 		if (riic->err)
153 			break;
154 
155 		start_bit = ICCR2_RS;
156 	}
157 
158  out:
159 	pm_runtime_put(adap->dev.parent);
160 
161 	return riic->err ?: num;
162 }
163 
164 static irqreturn_t riic_tdre_isr(int irq, void *data)
165 {
166 	struct riic_dev *riic = data;
167 	u8 val;
168 
169 	if (!riic->bytes_left)
170 		return IRQ_NONE;
171 
172 	if (riic->bytes_left == RIIC_INIT_MSG) {
173 		if (riic->msg->flags & I2C_M_RD)
174 			/* On read, switch over to receive interrupt */
175 			riic_clear_set_bit(riic, ICIER_TIE, ICIER_RIE, RIIC_ICIER);
176 		else
177 			/* On write, initialize length */
178 			riic->bytes_left = riic->msg->len;
179 
180 		val = i2c_8bit_addr_from_msg(riic->msg);
181 	} else {
182 		val = *riic->buf;
183 		riic->buf++;
184 		riic->bytes_left--;
185 	}
186 
187 	/*
188 	 * Switch to transmission ended interrupt when done. Do check here
189 	 * after bytes_left was initialized to support SMBUS_QUICK (new msg has
190 	 * 0 length then)
191 	 */
192 	if (riic->bytes_left == 0)
193 		riic_clear_set_bit(riic, ICIER_TIE, ICIER_TEIE, RIIC_ICIER);
194 
195 	/*
196 	 * This acks the TIE interrupt. We get another TIE immediately if our
197 	 * value could be moved to the shadow shift register right away. So
198 	 * this must be after updates to ICIER (where we want to disable TIE)!
199 	 */
200 	writeb(val, riic->base + RIIC_ICDRT);
201 
202 	return IRQ_HANDLED;
203 }
204 
205 static irqreturn_t riic_tend_isr(int irq, void *data)
206 {
207 	struct riic_dev *riic = data;
208 
209 	if (readb(riic->base + RIIC_ICSR2) & ICSR2_NACKF) {
210 		/* We got a NACKIE */
211 		readb(riic->base + RIIC_ICDRR);	/* dummy read */
212 		riic_clear_set_bit(riic, ICSR2_NACKF, 0, RIIC_ICSR2);
213 		riic->err = -ENXIO;
214 	} else if (riic->bytes_left) {
215 		return IRQ_NONE;
216 	}
217 
218 	if (riic->is_last || riic->err) {
219 		riic_clear_set_bit(riic, ICIER_TEIE, ICIER_SPIE, RIIC_ICIER);
220 		writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
221 	} else {
222 		/* Transfer is complete, but do not send STOP */
223 		riic_clear_set_bit(riic, ICIER_TEIE, 0, RIIC_ICIER);
224 		complete(&riic->msg_done);
225 	}
226 
227 	return IRQ_HANDLED;
228 }
229 
230 static irqreturn_t riic_rdrf_isr(int irq, void *data)
231 {
232 	struct riic_dev *riic = data;
233 
234 	if (!riic->bytes_left)
235 		return IRQ_NONE;
236 
237 	if (riic->bytes_left == RIIC_INIT_MSG) {
238 		riic->bytes_left = riic->msg->len;
239 		readb(riic->base + RIIC_ICDRR);	/* dummy read */
240 		return IRQ_HANDLED;
241 	}
242 
243 	if (riic->bytes_left == 1) {
244 		/* STOP must come before we set ACKBT! */
245 		if (riic->is_last) {
246 			riic_clear_set_bit(riic, 0, ICIER_SPIE, RIIC_ICIER);
247 			writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
248 		}
249 
250 		riic_clear_set_bit(riic, 0, ICMR3_ACKBT, RIIC_ICMR3);
251 
252 	} else {
253 		riic_clear_set_bit(riic, ICMR3_ACKBT, 0, RIIC_ICMR3);
254 	}
255 
256 	/* Reading acks the RIE interrupt */
257 	*riic->buf = readb(riic->base + RIIC_ICDRR);
258 	riic->buf++;
259 	riic->bytes_left--;
260 
261 	return IRQ_HANDLED;
262 }
263 
264 static irqreturn_t riic_stop_isr(int irq, void *data)
265 {
266 	struct riic_dev *riic = data;
267 
268 	/* read back registers to confirm writes have fully propagated */
269 	writeb(0, riic->base + RIIC_ICSR2);
270 	readb(riic->base + RIIC_ICSR2);
271 	writeb(0, riic->base + RIIC_ICIER);
272 	readb(riic->base + RIIC_ICIER);
273 
274 	complete(&riic->msg_done);
275 
276 	return IRQ_HANDLED;
277 }
278 
279 static u32 riic_func(struct i2c_adapter *adap)
280 {
281 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
282 }
283 
284 static const struct i2c_algorithm riic_algo = {
285 	.master_xfer	= riic_xfer,
286 	.functionality	= riic_func,
287 };
288 
289 static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
290 {
291 	int ret = 0;
292 	unsigned long rate;
293 	int total_ticks, cks, brl, brh;
294 
295 	pm_runtime_get_sync(riic->adapter.dev.parent);
296 
297 	if (t->bus_freq_hz > I2C_MAX_FAST_MODE_FREQ) {
298 		dev_err(&riic->adapter.dev,
299 			"unsupported bus speed (%dHz). %d max\n",
300 			t->bus_freq_hz, I2C_MAX_FAST_MODE_FREQ);
301 		ret = -EINVAL;
302 		goto out;
303 	}
304 
305 	rate = clk_get_rate(riic->clk);
306 
307 	/*
308 	 * Assume the default register settings:
309 	 *  FER.SCLE = 1 (SCL sync circuit enabled, adds 2 or 3 cycles)
310 	 *  FER.NFE = 1 (noise circuit enabled)
311 	 *  MR3.NF = 0 (1 cycle of noise filtered out)
312 	 *
313 	 * Freq (CKS=000) = (I2CCLK + tr + tf)/ (BRH + 3 + 1) + (BRL + 3 + 1)
314 	 * Freq (CKS!=000) = (I2CCLK + tr + tf)/ (BRH + 2 + 1) + (BRL + 2 + 1)
315 	 */
316 
317 	/*
318 	 * Determine reference clock rate. We must be able to get the desired
319 	 * frequency with only 62 clock ticks max (31 high, 31 low).
320 	 * Aim for a duty of 60% LOW, 40% HIGH.
321 	 */
322 	total_ticks = DIV_ROUND_UP(rate, t->bus_freq_hz);
323 
324 	for (cks = 0; cks < 7; cks++) {
325 		/*
326 		 * 60% low time must be less than BRL + 2 + 1
327 		 * BRL max register value is 0x1F.
328 		 */
329 		brl = ((total_ticks * 6) / 10);
330 		if (brl <= (0x1F + 3))
331 			break;
332 
333 		total_ticks /= 2;
334 		rate /= 2;
335 	}
336 
337 	if (brl > (0x1F + 3)) {
338 		dev_err(&riic->adapter.dev, "invalid speed (%lu). Too slow.\n",
339 			(unsigned long)t->bus_freq_hz);
340 		ret = -EINVAL;
341 		goto out;
342 	}
343 
344 	brh = total_ticks - brl;
345 
346 	/* Remove automatic clock ticks for sync circuit and NF */
347 	if (cks == 0) {
348 		brl -= 4;
349 		brh -= 4;
350 	} else {
351 		brl -= 3;
352 		brh -= 3;
353 	}
354 
355 	/*
356 	 * Remove clock ticks for rise and fall times. Convert ns to clock
357 	 * ticks.
358 	 */
359 	brl -= t->scl_fall_ns / (1000000000 / rate);
360 	brh -= t->scl_rise_ns / (1000000000 / rate);
361 
362 	/* Adjust for min register values for when SCLE=1 and NFE=1 */
363 	if (brl < 1)
364 		brl = 1;
365 	if (brh < 1)
366 		brh = 1;
367 
368 	pr_debug("i2c-riic: freq=%lu, duty=%d, fall=%lu, rise=%lu, cks=%d, brl=%d, brh=%d\n",
369 		 rate / total_ticks, ((brl + 3) * 100) / (brl + brh + 6),
370 		 t->scl_fall_ns / (1000000000 / rate),
371 		 t->scl_rise_ns / (1000000000 / rate), cks, brl, brh);
372 
373 	/* Changing the order of accessing IICRST and ICE may break things! */
374 	writeb(ICCR1_IICRST | ICCR1_SOWP, riic->base + RIIC_ICCR1);
375 	riic_clear_set_bit(riic, 0, ICCR1_ICE, RIIC_ICCR1);
376 
377 	writeb(ICMR1_CKS(cks), riic->base + RIIC_ICMR1);
378 	writeb(brh | ICBR_RESERVED, riic->base + RIIC_ICBRH);
379 	writeb(brl | ICBR_RESERVED, riic->base + RIIC_ICBRL);
380 
381 	writeb(0, riic->base + RIIC_ICSER);
382 	writeb(ICMR3_ACKWP | ICMR3_RDRFS, riic->base + RIIC_ICMR3);
383 
384 	riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);
385 
386 out:
387 	pm_runtime_put(riic->adapter.dev.parent);
388 	return ret;
389 }
390 
391 static struct riic_irq_desc riic_irqs[] = {
392 	{ .res_num = 0, .isr = riic_tend_isr, .name = "riic-tend" },
393 	{ .res_num = 1, .isr = riic_rdrf_isr, .name = "riic-rdrf" },
394 	{ .res_num = 2, .isr = riic_tdre_isr, .name = "riic-tdre" },
395 	{ .res_num = 3, .isr = riic_stop_isr, .name = "riic-stop" },
396 	{ .res_num = 5, .isr = riic_tend_isr, .name = "riic-nack" },
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 	enum riic_type type;
408 
409 	riic = devm_kzalloc(&pdev->dev, sizeof(*riic), GFP_KERNEL);
410 	if (!riic)
411 		return -ENOMEM;
412 
413 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
414 	riic->base = devm_ioremap_resource(&pdev->dev, res);
415 	if (IS_ERR(riic->base))
416 		return PTR_ERR(riic->base);
417 
418 	riic->clk = devm_clk_get(&pdev->dev, NULL);
419 	if (IS_ERR(riic->clk)) {
420 		dev_err(&pdev->dev, "missing controller clock");
421 		return PTR_ERR(riic->clk);
422 	}
423 
424 	type = (enum riic_type)of_device_get_match_data(&pdev->dev);
425 	if (type == RIIC_RZ_G2L) {
426 		rstc = devm_reset_control_get_exclusive(&pdev->dev, NULL);
427 		if (IS_ERR(rstc)) {
428 			dev_err(&pdev->dev, "Error: missing reset ctrl\n");
429 			return PTR_ERR(rstc);
430 		}
431 
432 		reset_control_deassert(rstc);
433 	}
434 
435 	for (i = 0; i < ARRAY_SIZE(riic_irqs); i++) {
436 		res = platform_get_resource(pdev, IORESOURCE_IRQ, riic_irqs[i].res_num);
437 		if (!res)
438 			return -ENODEV;
439 
440 		ret = devm_request_irq(&pdev->dev, res->start, riic_irqs[i].isr,
441 					0, riic_irqs[i].name, riic);
442 		if (ret) {
443 			dev_err(&pdev->dev, "failed to request irq %s\n", riic_irqs[i].name);
444 			return ret;
445 		}
446 	}
447 
448 	adap = &riic->adapter;
449 	i2c_set_adapdata(adap, riic);
450 	strlcpy(adap->name, "Renesas RIIC adapter", sizeof(adap->name));
451 	adap->owner = THIS_MODULE;
452 	adap->algo = &riic_algo;
453 	adap->dev.parent = &pdev->dev;
454 	adap->dev.of_node = pdev->dev.of_node;
455 
456 	init_completion(&riic->msg_done);
457 
458 	i2c_parse_fw_timings(&pdev->dev, &i2c_t, true);
459 
460 	pm_runtime_enable(&pdev->dev);
461 
462 	ret = riic_init_hw(riic, &i2c_t);
463 	if (ret)
464 		goto out;
465 
466 	ret = i2c_add_adapter(adap);
467 	if (ret)
468 		goto out;
469 
470 	platform_set_drvdata(pdev, riic);
471 
472 	dev_info(&pdev->dev, "registered with %dHz bus speed\n",
473 		 i2c_t.bus_freq_hz);
474 	return 0;
475 
476 out:
477 	pm_runtime_disable(&pdev->dev);
478 	return ret;
479 }
480 
481 static int riic_i2c_remove(struct platform_device *pdev)
482 {
483 	struct riic_dev *riic = platform_get_drvdata(pdev);
484 
485 	pm_runtime_get_sync(&pdev->dev);
486 	writeb(0, riic->base + RIIC_ICIER);
487 	pm_runtime_put(&pdev->dev);
488 	i2c_del_adapter(&riic->adapter);
489 	pm_runtime_disable(&pdev->dev);
490 
491 	return 0;
492 }
493 
494 static const struct of_device_id riic_i2c_dt_ids[] = {
495 	{ .compatible = "renesas,riic-r9a07g044", .data = (void *)RIIC_RZ_G2L },
496 	{ .compatible = "renesas,riic-rz", .data = (void *)RIIC_RZ_A },
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