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
i2c_lpc2k_reset(struct lpc2k_i2c * i2c)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
i2c_lpc2k_clear_arb(struct lpc2k_i2c * i2c)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
i2c_lpc2k_pump_msg(struct lpc2k_i2c * i2c)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
lpc2k_process_msg(struct lpc2k_i2c * i2c,int msgidx)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
i2c_lpc2k_xfer(struct i2c_adapter * adap,struct i2c_msg * msgs,int msg_num)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
i2c_lpc2k_handler(int irq,void * dev_id)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
i2c_lpc2k_functionality(struct i2c_adapter * adap)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
i2c_lpc2k_probe(struct platform_device * pdev)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
i2c_lpc2k_remove(struct platform_device * dev)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
i2c_lpc2k_suspend(struct device * dev)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
i2c_lpc2k_resume(struct device * dev)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
