xref: /openbmc/linux/drivers/i2c/busses/i2c-lpc2k.c (revision 3ddc8b84) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright (C) 2011 NXP Semiconductors
4  *
5  * Code portions referenced from the i2x-pxa and i2c-pnx drivers
6  *
7  * Make SMBus byte and word transactions work on LPC178x/7x
8  * Copyright (c) 2012
9  * Alexander Potashev, Emcraft Systems, aspotashev@emcraft.com
10  * Anton Protopopov, Emcraft Systems, antonp@emcraft.com
11  *
12  * Copyright (C) 2015 Joachim Eastwood <manabian@gmail.com>
13  */
14 
15 #include <linux/clk.h>
16 #include <linux/errno.h>
17 #include <linux/i2c.h>
18 #include <linux/interrupt.h>
19 #include <linux/io.h>
20 #include <linux/kernel.h>
21 #include <linux/module.h>
22 #include <linux/of.h>
23 #include <linux/platform_device.h>
24 #include <linux/sched.h>
25 #include <linux/time.h>
26 
27 /* LPC24xx register offsets and bits */
28 #define LPC24XX_I2CONSET	0x00
29 #define LPC24XX_I2STAT		0x04
30 #define LPC24XX_I2DAT		0x08
31 #define LPC24XX_I2ADDR		0x0c
32 #define LPC24XX_I2SCLH		0x10
33 #define LPC24XX_I2SCLL		0x14
34 #define LPC24XX_I2CONCLR	0x18
35 
36 #define LPC24XX_AA		BIT(2)
37 #define LPC24XX_SI		BIT(3)
38 #define LPC24XX_STO		BIT(4)
39 #define LPC24XX_STA		BIT(5)
40 #define LPC24XX_I2EN		BIT(6)
41 
42 #define LPC24XX_STO_AA		(LPC24XX_STO | LPC24XX_AA)
43 #define LPC24XX_CLEAR_ALL	(LPC24XX_AA | LPC24XX_SI | LPC24XX_STO | \
44 				 LPC24XX_STA | LPC24XX_I2EN)
45 
46 /* I2C SCL clock has different duty cycle depending on mode */
47 #define I2C_STD_MODE_DUTY		46
48 #define I2C_FAST_MODE_DUTY		36
49 #define I2C_FAST_MODE_PLUS_DUTY		38
50 
51 /*
52  * 26 possible I2C status codes, but codes applicable only
53  * to master are listed here and used in this driver
54  */
55 enum {
56 	M_BUS_ERROR		= 0x00,
57 	M_START			= 0x08,
58 	M_REPSTART		= 0x10,
59 	MX_ADDR_W_ACK		= 0x18,
60 	MX_ADDR_W_NACK		= 0x20,
61 	MX_DATA_W_ACK		= 0x28,
62 	MX_DATA_W_NACK		= 0x30,
63 	M_DATA_ARB_LOST		= 0x38,
64 	MR_ADDR_R_ACK		= 0x40,
65 	MR_ADDR_R_NACK		= 0x48,
66 	MR_DATA_R_ACK		= 0x50,
67 	MR_DATA_R_NACK		= 0x58,
68 	M_I2C_IDLE		= 0xf8,
69 };
70 
71 struct lpc2k_i2c {
72 	void __iomem		*base;
73 	struct clk		*clk;
74 	int			irq;
75 	wait_queue_head_t	wait;
76 	struct i2c_adapter	adap;
77 	struct i2c_msg		*msg;
78 	int			msg_idx;
79 	int			msg_status;
80 	int			is_last;
81 };
82 
83 static void i2c_lpc2k_reset(struct lpc2k_i2c *i2c)
84 {
85 	/* Will force clear all statuses */
86 	writel(LPC24XX_CLEAR_ALL, i2c->base + LPC24XX_I2CONCLR);
87 	writel(0, i2c->base + LPC24XX_I2ADDR);
88 	writel(LPC24XX_I2EN, i2c->base + LPC24XX_I2CONSET);
89 }
90 
91 static int i2c_lpc2k_clear_arb(struct lpc2k_i2c *i2c)
92 {
93 	unsigned long timeout = jiffies + msecs_to_jiffies(1000);
94 
95 	/*
96 	 * If the transfer needs to abort for some reason, we'll try to
97 	 * force a stop condition to clear any pending bus conditions
98 	 */
99 	writel(LPC24XX_STO, i2c->base + LPC24XX_I2CONSET);
100 
101 	/* Wait for status change */
102 	while (readl(i2c->base + LPC24XX_I2STAT) != M_I2C_IDLE) {
103 		if (time_after(jiffies, timeout)) {
104 			/* Bus was not idle, try to reset adapter */
105 			i2c_lpc2k_reset(i2c);
106 			return -EBUSY;
107 		}
108 
109 		cpu_relax();
110 	}
111 
112 	return 0;
113 }
114 
115 static void i2c_lpc2k_pump_msg(struct lpc2k_i2c *i2c)
116 {
117 	unsigned char data;
118 	u32 status;
119 
120 	/*
121 	 * I2C in the LPC2xxx series is basically a state machine.
122 	 * Just run through the steps based on the current status.
123 	 */
124 	status = readl(i2c->base + LPC24XX_I2STAT);
125 
126 	switch (status) {
127 	case M_START:
128 	case M_REPSTART:
129 		/* Start bit was just sent out, send out addr and dir */
130 		data = i2c_8bit_addr_from_msg(i2c->msg);
131 
132 		writel(data, i2c->base + LPC24XX_I2DAT);
133 		writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
134 		break;
135 
136 	case MX_ADDR_W_ACK:
137 	case MX_DATA_W_ACK:
138 		/*
139 		 * Address or data was sent out with an ACK. If there is more
140 		 * data to send, send it now
141 		 */
142 		if (i2c->msg_idx < i2c->msg->len) {
143 			writel(i2c->msg->buf[i2c->msg_idx],
144 			       i2c->base + LPC24XX_I2DAT);
145 		} else if (i2c->is_last) {
146 			/* Last message, send stop */
147 			writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
148 			writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
149 			i2c->msg_status = 0;
150 			disable_irq_nosync(i2c->irq);
151 		} else {
152 			i2c->msg_status = 0;
153 			disable_irq_nosync(i2c->irq);
154 		}
155 
156 		i2c->msg_idx++;
157 		break;
158 
159 	case MR_ADDR_R_ACK:
160 		/* Receive first byte from slave */
161 		if (i2c->msg->len == 1) {
162 			/* Last byte, return NACK */
163 			writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONCLR);
164 		} else {
165 			/* Not last byte, return ACK */
166 			writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONSET);
167 		}
168 
169 		writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
170 		break;
171 
172 	case MR_DATA_R_NACK:
173 		/*
174 		 * The I2C shows NACK status on reads, so we need to accept
175 		 * the NACK as an ACK here. This should be ok, as the real
176 		 * BACK would of been caught on the address write.
177 		 */
178 	case MR_DATA_R_ACK:
179 		/* Data was received */
180 		if (i2c->msg_idx < i2c->msg->len) {
181 			i2c->msg->buf[i2c->msg_idx] =
182 					readl(i2c->base + LPC24XX_I2DAT);
183 		}
184 
185 		/* If transfer is done, send STOP */
186 		if (i2c->msg_idx >= i2c->msg->len - 1 && i2c->is_last) {
187 			writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
188 			writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
189 			i2c->msg_status = 0;
190 		}
191 
192 		/* Message is done */
193 		if (i2c->msg_idx >= i2c->msg->len - 1) {
194 			i2c->msg_status = 0;
195 			disable_irq_nosync(i2c->irq);
196 		}
197 
198 		/*
199 		 * One pre-last data input, send NACK to tell the slave that
200 		 * this is going to be the last data byte to be transferred.
201 		 */
202 		if (i2c->msg_idx >= i2c->msg->len - 2) {
203 			/* One byte left to receive - NACK */
204 			writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONCLR);
205 		} else {
206 			/* More than one byte left to receive - ACK */
207 			writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONSET);
208 		}
209 
210 		writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
211 		i2c->msg_idx++;
212 		break;
213 
214 	case MX_ADDR_W_NACK:
215 	case MX_DATA_W_NACK:
216 	case MR_ADDR_R_NACK:
217 		/* NACK processing is done */
218 		writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
219 		i2c->msg_status = -ENXIO;
220 		disable_irq_nosync(i2c->irq);
221 		break;
222 
223 	case M_DATA_ARB_LOST:
224 		/* Arbitration lost */
225 		i2c->msg_status = -EAGAIN;
226 
227 		/* Release the I2C bus */
228 		writel(LPC24XX_STA | LPC24XX_STO, i2c->base + LPC24XX_I2CONCLR);
229 		disable_irq_nosync(i2c->irq);
230 		break;
231 
232 	default:
233 		/* Unexpected statuses */
234 		i2c->msg_status = -EIO;
235 		disable_irq_nosync(i2c->irq);
236 		break;
237 	}
238 
239 	/* Exit on failure or all bytes transferred */
240 	if (i2c->msg_status != -EBUSY)
241 		wake_up(&i2c->wait);
242 
243 	/*
244 	 * If `msg_status` is zero, then `lpc2k_process_msg()`
245 	 * is responsible for clearing the SI flag.
246 	 */
247 	if (i2c->msg_status != 0)
248 		writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
249 }
250 
251 static int lpc2k_process_msg(struct lpc2k_i2c *i2c, int msgidx)
252 {
253 	/* A new transfer is kicked off by initiating a start condition */
254 	if (!msgidx) {
255 		writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONSET);
256 	} else {
257 		/*
258 		 * A multi-message I2C transfer continues where the
259 		 * previous I2C transfer left off and uses the
260 		 * current condition of the I2C adapter.
261 		 */
262 		if (unlikely(i2c->msg->flags & I2C_M_NOSTART)) {
263 			WARN_ON(i2c->msg->len == 0);
264 
265 			if (!(i2c->msg->flags & I2C_M_RD)) {
266 				/* Start transmit of data */
267 				writel(i2c->msg->buf[0],
268 				       i2c->base + LPC24XX_I2DAT);
269 				i2c->msg_idx++;
270 			}
271 		} else {
272 			/* Start or repeated start */
273 			writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONSET);
274 		}
275 
276 		writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
277 	}
278 
279 	enable_irq(i2c->irq);
280 
281 	/* Wait for transfer completion */
282 	if (wait_event_timeout(i2c->wait, i2c->msg_status != -EBUSY,
283 			       msecs_to_jiffies(1000)) == 0) {
284 		disable_irq_nosync(i2c->irq);
285 
286 		return -ETIMEDOUT;
287 	}
288 
289 	return i2c->msg_status;
290 }
291 
292 static int i2c_lpc2k_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
293 			  int msg_num)
294 {
295 	struct lpc2k_i2c *i2c = i2c_get_adapdata(adap);
296 	int ret, i;
297 	u32 stat;
298 
299 	/* Check for bus idle condition */
300 	stat = readl(i2c->base + LPC24XX_I2STAT);
301 	if (stat != M_I2C_IDLE) {
302 		/* Something is holding the bus, try to clear it */
303 		return i2c_lpc2k_clear_arb(i2c);
304 	}
305 
306 	/* Process a single message at a time */
307 	for (i = 0; i < msg_num; i++) {
308 		/* Save message pointer and current message data index */
309 		i2c->msg = &msgs[i];
310 		i2c->msg_idx = 0;
311 		i2c->msg_status = -EBUSY;
312 		i2c->is_last = (i == (msg_num - 1));
313 
314 		ret = lpc2k_process_msg(i2c, i);
315 		if (ret)
316 			return ret;
317 	}
318 
319 	return msg_num;
320 }
321 
322 static irqreturn_t i2c_lpc2k_handler(int irq, void *dev_id)
323 {
324 	struct lpc2k_i2c *i2c = dev_id;
325 
326 	if (readl(i2c->base + LPC24XX_I2CONSET) & LPC24XX_SI) {
327 		i2c_lpc2k_pump_msg(i2c);
328 		return IRQ_HANDLED;
329 	}
330 
331 	return IRQ_NONE;
332 }
333 
334 static u32 i2c_lpc2k_functionality(struct i2c_adapter *adap)
335 {
336 	/* Only emulated SMBus for now */
337 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
338 }
339 
340 static const struct i2c_algorithm i2c_lpc2k_algorithm = {
341 	.master_xfer	= i2c_lpc2k_xfer,
342 	.functionality	= i2c_lpc2k_functionality,
343 };
344 
345 static int i2c_lpc2k_probe(struct platform_device *pdev)
346 {
347 	struct lpc2k_i2c *i2c;
348 	u32 bus_clk_rate;
349 	u32 scl_high;
350 	u32 clkrate;
351 	int ret;
352 
353 	i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
354 	if (!i2c)
355 		return -ENOMEM;
356 
357 	i2c->base = devm_platform_ioremap_resource(pdev, 0);
358 	if (IS_ERR(i2c->base))
359 		return PTR_ERR(i2c->base);
360 
361 	i2c->irq = platform_get_irq(pdev, 0);
362 	if (i2c->irq < 0)
363 		return i2c->irq;
364 
365 	init_waitqueue_head(&i2c->wait);
366 
367 	i2c->clk = devm_clk_get_enabled(&pdev->dev, NULL);
368 	if (IS_ERR(i2c->clk)) {
369 		dev_err(&pdev->dev, "failed to enable clock.\n");
370 		return PTR_ERR(i2c->clk);
371 	}
372 
373 	ret = devm_request_irq(&pdev->dev, i2c->irq, i2c_lpc2k_handler, 0,
374 			       dev_name(&pdev->dev), i2c);
375 	if (ret < 0) {
376 		dev_err(&pdev->dev, "can't request interrupt.\n");
377 		return ret;
378 	}
379 
380 	disable_irq_nosync(i2c->irq);
381 
382 	/* Place controller is a known state */
383 	i2c_lpc2k_reset(i2c);
384 
385 	ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
386 				   &bus_clk_rate);
387 	if (ret)
388 		bus_clk_rate = I2C_MAX_STANDARD_MODE_FREQ;
389 
390 	clkrate = clk_get_rate(i2c->clk);
391 	if (clkrate == 0) {
392 		dev_err(&pdev->dev, "can't get I2C base clock\n");
393 		return -EINVAL;
394 	}
395 
396 	/* Setup I2C dividers to generate clock with proper duty cycle */
397 	clkrate = clkrate / bus_clk_rate;
398 	if (bus_clk_rate <= I2C_MAX_STANDARD_MODE_FREQ)
399 		scl_high = (clkrate * I2C_STD_MODE_DUTY) / 100;
400 	else if (bus_clk_rate <= I2C_MAX_FAST_MODE_FREQ)
401 		scl_high = (clkrate * I2C_FAST_MODE_DUTY) / 100;
402 	else
403 		scl_high = (clkrate * I2C_FAST_MODE_PLUS_DUTY) / 100;
404 
405 	writel(scl_high, i2c->base + LPC24XX_I2SCLH);
406 	writel(clkrate - scl_high, i2c->base + LPC24XX_I2SCLL);
407 
408 	platform_set_drvdata(pdev, i2c);
409 
410 	i2c_set_adapdata(&i2c->adap, i2c);
411 	i2c->adap.owner = THIS_MODULE;
412 	strscpy(i2c->adap.name, "LPC2K I2C adapter", sizeof(i2c->adap.name));
413 	i2c->adap.algo = &i2c_lpc2k_algorithm;
414 	i2c->adap.dev.parent = &pdev->dev;
415 	i2c->adap.dev.of_node = pdev->dev.of_node;
416 
417 	ret = i2c_add_adapter(&i2c->adap);
418 	if (ret < 0)
419 		return ret;
420 
421 	dev_info(&pdev->dev, "LPC2K I2C adapter\n");
422 
423 	return 0;
424 }
425 
426 static void i2c_lpc2k_remove(struct platform_device *dev)
427 {
428 	struct lpc2k_i2c *i2c = platform_get_drvdata(dev);
429 
430 	i2c_del_adapter(&i2c->adap);
431 }
432 
433 static int i2c_lpc2k_suspend(struct device *dev)
434 {
435 	struct lpc2k_i2c *i2c = dev_get_drvdata(dev);
436 
437 	clk_disable(i2c->clk);
438 
439 	return 0;
440 }
441 
442 static int i2c_lpc2k_resume(struct device *dev)
443 {
444 	struct lpc2k_i2c *i2c = dev_get_drvdata(dev);
445 
446 	clk_enable(i2c->clk);
447 	i2c_lpc2k_reset(i2c);
448 
449 	return 0;
450 }
451 
452 static const struct dev_pm_ops i2c_lpc2k_dev_pm_ops = {
453 	.suspend_noirq = i2c_lpc2k_suspend,
454 	.resume_noirq = i2c_lpc2k_resume,
455 };
456 
457 static const struct of_device_id lpc2k_i2c_match[] = {
458 	{ .compatible = "nxp,lpc1788-i2c" },
459 	{},
460 };
461 MODULE_DEVICE_TABLE(of, lpc2k_i2c_match);
462 
463 static struct platform_driver i2c_lpc2k_driver = {
464 	.probe	= i2c_lpc2k_probe,
465 	.remove_new = i2c_lpc2k_remove,
466 	.driver	= {
467 		.name		= "lpc2k-i2c",
468 		.pm		= pm_sleep_ptr(&i2c_lpc2k_dev_pm_ops),
469 		.of_match_table	= lpc2k_i2c_match,
470 	},
471 };
472 module_platform_driver(i2c_lpc2k_driver);
473 
474 MODULE_AUTHOR("Kevin Wells <kevin.wells@nxp.com>");
475 MODULE_DESCRIPTION("I2C driver for LPC2xxx devices");
476 MODULE_LICENSE("GPL");
477 MODULE_ALIAS("platform:lpc2k-i2c");
478