1 /*
2  * Copyright (C) 2014 Broadcom Corporation
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License as
6  * published by the Free Software Foundation version 2.
7  *
8  * This program is distributed "as is" WITHOUT ANY WARRANTY of any
9  * kind, whether express or implied; without even the implied warranty
10  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11  * GNU General Public License for more details.
12  */
13 
14 #include <linux/delay.h>
15 #include <linux/i2c.h>
16 #include <linux/interrupt.h>
17 #include <linux/io.h>
18 #include <linux/kernel.h>
19 #include <linux/module.h>
20 #include <linux/platform_device.h>
21 #include <linux/slab.h>
22 
23 #define CFG_OFFSET                   0x00
24 #define CFG_RESET_SHIFT              31
25 #define CFG_EN_SHIFT                 30
26 #define CFG_M_RETRY_CNT_SHIFT        16
27 #define CFG_M_RETRY_CNT_MASK         0x0f
28 
29 #define TIM_CFG_OFFSET               0x04
30 #define TIM_CFG_MODE_400_SHIFT       31
31 
32 #define M_FIFO_CTRL_OFFSET           0x0c
33 #define M_FIFO_RX_FLUSH_SHIFT        31
34 #define M_FIFO_TX_FLUSH_SHIFT        30
35 #define M_FIFO_RX_CNT_SHIFT          16
36 #define M_FIFO_RX_CNT_MASK           0x7f
37 #define M_FIFO_RX_THLD_SHIFT         8
38 #define M_FIFO_RX_THLD_MASK          0x3f
39 
40 #define M_CMD_OFFSET                 0x30
41 #define M_CMD_START_BUSY_SHIFT       31
42 #define M_CMD_STATUS_SHIFT           25
43 #define M_CMD_STATUS_MASK            0x07
44 #define M_CMD_STATUS_SUCCESS         0x0
45 #define M_CMD_STATUS_LOST_ARB        0x1
46 #define M_CMD_STATUS_NACK_ADDR       0x2
47 #define M_CMD_STATUS_NACK_DATA       0x3
48 #define M_CMD_STATUS_TIMEOUT         0x4
49 #define M_CMD_PROTOCOL_SHIFT         9
50 #define M_CMD_PROTOCOL_MASK          0xf
51 #define M_CMD_PROTOCOL_BLK_WR        0x7
52 #define M_CMD_PROTOCOL_BLK_RD        0x8
53 #define M_CMD_PEC_SHIFT              8
54 #define M_CMD_RD_CNT_SHIFT           0
55 #define M_CMD_RD_CNT_MASK            0xff
56 
57 #define IE_OFFSET                    0x38
58 #define IE_M_RX_FIFO_FULL_SHIFT      31
59 #define IE_M_RX_THLD_SHIFT           30
60 #define IE_M_START_BUSY_SHIFT        28
61 #define IE_M_TX_UNDERRUN_SHIFT       27
62 
63 #define IS_OFFSET                    0x3c
64 #define IS_M_RX_FIFO_FULL_SHIFT      31
65 #define IS_M_RX_THLD_SHIFT           30
66 #define IS_M_START_BUSY_SHIFT        28
67 #define IS_M_TX_UNDERRUN_SHIFT       27
68 
69 #define M_TX_OFFSET                  0x40
70 #define M_TX_WR_STATUS_SHIFT         31
71 #define M_TX_DATA_SHIFT              0
72 #define M_TX_DATA_MASK               0xff
73 
74 #define M_RX_OFFSET                  0x44
75 #define M_RX_STATUS_SHIFT            30
76 #define M_RX_STATUS_MASK             0x03
77 #define M_RX_PEC_ERR_SHIFT           29
78 #define M_RX_DATA_SHIFT              0
79 #define M_RX_DATA_MASK               0xff
80 
81 #define I2C_TIMEOUT_MSEC             50000
82 #define M_TX_RX_FIFO_SIZE            64
83 
84 enum bus_speed_index {
85 	I2C_SPD_100K = 0,
86 	I2C_SPD_400K,
87 };
88 
89 struct bcm_iproc_i2c_dev {
90 	struct device *device;
91 	int irq;
92 
93 	void __iomem *base;
94 
95 	struct i2c_adapter adapter;
96 	unsigned int bus_speed;
97 
98 	struct completion done;
99 	int xfer_is_done;
100 
101 	struct i2c_msg *msg;
102 
103 	/* bytes that have been transferred */
104 	unsigned int tx_bytes;
105 };
106 
107 /*
108  * Can be expanded in the future if more interrupt status bits are utilized
109  */
110 #define ISR_MASK (BIT(IS_M_START_BUSY_SHIFT) | BIT(IS_M_TX_UNDERRUN_SHIFT))
111 
112 static irqreturn_t bcm_iproc_i2c_isr(int irq, void *data)
113 {
114 	struct bcm_iproc_i2c_dev *iproc_i2c = data;
115 	u32 status = readl(iproc_i2c->base + IS_OFFSET);
116 
117 	status &= ISR_MASK;
118 
119 	if (!status)
120 		return IRQ_NONE;
121 
122 	/* TX FIFO is empty and we have more data to send */
123 	if (status & BIT(IS_M_TX_UNDERRUN_SHIFT)) {
124 		struct i2c_msg *msg = iproc_i2c->msg;
125 		unsigned int tx_bytes = msg->len - iproc_i2c->tx_bytes;
126 		unsigned int i;
127 		u32 val;
128 
129 		/* can only fill up to the FIFO size */
130 		tx_bytes = min_t(unsigned int, tx_bytes, M_TX_RX_FIFO_SIZE);
131 		for (i = 0; i < tx_bytes; i++) {
132 			/* start from where we left over */
133 			unsigned int idx = iproc_i2c->tx_bytes + i;
134 
135 			val = msg->buf[idx];
136 
137 			/* mark the last byte */
138 			if (idx == msg->len - 1) {
139 				u32 tmp;
140 
141 				val |= BIT(M_TX_WR_STATUS_SHIFT);
142 
143 				/*
144 				 * Since this is the last byte, we should
145 				 * now disable TX FIFO underrun interrupt
146 				 */
147 				tmp = readl(iproc_i2c->base + IE_OFFSET);
148 				tmp &= ~BIT(IE_M_TX_UNDERRUN_SHIFT);
149 				writel(tmp, iproc_i2c->base + IE_OFFSET);
150 			}
151 
152 			/* load data into TX FIFO */
153 			writel(val, iproc_i2c->base + M_TX_OFFSET);
154 		}
155 		/* update number of transferred bytes */
156 		iproc_i2c->tx_bytes += tx_bytes;
157 	}
158 
159 	if (status & BIT(IS_M_START_BUSY_SHIFT)) {
160 		iproc_i2c->xfer_is_done = 1;
161 		complete(&iproc_i2c->done);
162 	}
163 
164 	writel(status, iproc_i2c->base + IS_OFFSET);
165 
166 	return IRQ_HANDLED;
167 }
168 
169 static int bcm_iproc_i2c_init(struct bcm_iproc_i2c_dev *iproc_i2c)
170 {
171 	u32 val;
172 
173 	/* put controller in reset */
174 	val = readl(iproc_i2c->base + CFG_OFFSET);
175 	val |= 1 << CFG_RESET_SHIFT;
176 	val &= ~(1 << CFG_EN_SHIFT);
177 	writel(val, iproc_i2c->base + CFG_OFFSET);
178 
179 	/* wait 100 usec per spec */
180 	udelay(100);
181 
182 	/* bring controller out of reset */
183 	val &= ~(1 << CFG_RESET_SHIFT);
184 	writel(val, iproc_i2c->base + CFG_OFFSET);
185 
186 	/* flush TX/RX FIFOs and set RX FIFO threshold to zero */
187 	val = (1 << M_FIFO_RX_FLUSH_SHIFT) | (1 << M_FIFO_TX_FLUSH_SHIFT);
188 	writel(val, iproc_i2c->base + M_FIFO_CTRL_OFFSET);
189 	/* disable all interrupts */
190 	writel(0, iproc_i2c->base + IE_OFFSET);
191 
192 	/* clear all pending interrupts */
193 	writel(0xffffffff, iproc_i2c->base + IS_OFFSET);
194 
195 	return 0;
196 }
197 
198 static void bcm_iproc_i2c_enable_disable(struct bcm_iproc_i2c_dev *iproc_i2c,
199 					 bool enable)
200 {
201 	u32 val;
202 
203 	val = readl(iproc_i2c->base + CFG_OFFSET);
204 	if (enable)
205 		val |= BIT(CFG_EN_SHIFT);
206 	else
207 		val &= ~BIT(CFG_EN_SHIFT);
208 	writel(val, iproc_i2c->base + CFG_OFFSET);
209 }
210 
211 static int bcm_iproc_i2c_check_status(struct bcm_iproc_i2c_dev *iproc_i2c,
212 				      struct i2c_msg *msg)
213 {
214 	u32 val;
215 
216 	val = readl(iproc_i2c->base + M_CMD_OFFSET);
217 	val = (val >> M_CMD_STATUS_SHIFT) & M_CMD_STATUS_MASK;
218 
219 	switch (val) {
220 	case M_CMD_STATUS_SUCCESS:
221 		return 0;
222 
223 	case M_CMD_STATUS_LOST_ARB:
224 		dev_dbg(iproc_i2c->device, "lost bus arbitration\n");
225 		return -EAGAIN;
226 
227 	case M_CMD_STATUS_NACK_ADDR:
228 		dev_dbg(iproc_i2c->device, "NAK addr:0x%02x\n", msg->addr);
229 		return -ENXIO;
230 
231 	case M_CMD_STATUS_NACK_DATA:
232 		dev_dbg(iproc_i2c->device, "NAK data\n");
233 		return -ENXIO;
234 
235 	case M_CMD_STATUS_TIMEOUT:
236 		dev_dbg(iproc_i2c->device, "bus timeout\n");
237 		return -ETIMEDOUT;
238 
239 	default:
240 		dev_dbg(iproc_i2c->device, "unknown error code=%d\n", val);
241 
242 		/* re-initialize i2c for recovery */
243 		bcm_iproc_i2c_enable_disable(iproc_i2c, false);
244 		bcm_iproc_i2c_init(iproc_i2c);
245 		bcm_iproc_i2c_enable_disable(iproc_i2c, true);
246 
247 		return -EIO;
248 	}
249 }
250 
251 static int bcm_iproc_i2c_xfer_single_msg(struct bcm_iproc_i2c_dev *iproc_i2c,
252 					 struct i2c_msg *msg)
253 {
254 	int ret, i;
255 	u8 addr;
256 	u32 val;
257 	unsigned int tx_bytes;
258 	unsigned long time_left = msecs_to_jiffies(I2C_TIMEOUT_MSEC);
259 
260 	/* check if bus is busy */
261 	if (!!(readl(iproc_i2c->base + M_CMD_OFFSET) &
262 	       BIT(M_CMD_START_BUSY_SHIFT))) {
263 		dev_warn(iproc_i2c->device, "bus is busy\n");
264 		return -EBUSY;
265 	}
266 
267 	iproc_i2c->msg = msg;
268 
269 	/* format and load slave address into the TX FIFO */
270 	addr = i2c_8bit_addr_from_msg(msg);
271 	writel(addr, iproc_i2c->base + M_TX_OFFSET);
272 
273 	/*
274 	 * For a write transaction, load data into the TX FIFO. Only allow
275 	 * loading up to TX FIFO size - 1 bytes of data since the first byte
276 	 * has been used up by the slave address
277 	 */
278 	tx_bytes = min_t(unsigned int, msg->len, M_TX_RX_FIFO_SIZE - 1);
279 	if (!(msg->flags & I2C_M_RD)) {
280 		for (i = 0; i < tx_bytes; i++) {
281 			val = msg->buf[i];
282 
283 			/* mark the last byte */
284 			if (i == msg->len - 1)
285 				val |= 1 << M_TX_WR_STATUS_SHIFT;
286 
287 			writel(val, iproc_i2c->base + M_TX_OFFSET);
288 		}
289 		iproc_i2c->tx_bytes = tx_bytes;
290 	}
291 
292 	/* mark as incomplete before starting the transaction */
293 	reinit_completion(&iproc_i2c->done);
294 	iproc_i2c->xfer_is_done = 0;
295 
296 	/*
297 	 * Enable the "start busy" interrupt, which will be triggered after the
298 	 * transaction is done, i.e., the internal start_busy bit, transitions
299 	 * from 1 to 0.
300 	 */
301 	val = BIT(IE_M_START_BUSY_SHIFT);
302 
303 	/*
304 	 * If TX data size is larger than the TX FIFO, need to enable TX
305 	 * underrun interrupt, which will be triggerred when the TX FIFO is
306 	 * empty. When that happens we can then pump more data into the FIFO
307 	 */
308 	if (!(msg->flags & I2C_M_RD) &&
309 	    msg->len > iproc_i2c->tx_bytes)
310 		val |= BIT(IE_M_TX_UNDERRUN_SHIFT);
311 
312 	writel(val, iproc_i2c->base + IE_OFFSET);
313 
314 	/*
315 	 * Now we can activate the transfer. For a read operation, specify the
316 	 * number of bytes to read
317 	 */
318 	val = BIT(M_CMD_START_BUSY_SHIFT);
319 	if (msg->flags & I2C_M_RD) {
320 		val |= (M_CMD_PROTOCOL_BLK_RD << M_CMD_PROTOCOL_SHIFT) |
321 		       (msg->len << M_CMD_RD_CNT_SHIFT);
322 	} else {
323 		val |= (M_CMD_PROTOCOL_BLK_WR << M_CMD_PROTOCOL_SHIFT);
324 	}
325 	writel(val, iproc_i2c->base + M_CMD_OFFSET);
326 
327 	time_left = wait_for_completion_timeout(&iproc_i2c->done, time_left);
328 
329 	/* disable all interrupts */
330 	writel(0, iproc_i2c->base + IE_OFFSET);
331 	/* read it back to flush the write */
332 	readl(iproc_i2c->base + IE_OFFSET);
333 
334 	/* make sure the interrupt handler isn't running */
335 	synchronize_irq(iproc_i2c->irq);
336 
337 	if (!time_left && !iproc_i2c->xfer_is_done) {
338 		dev_err(iproc_i2c->device, "transaction timed out\n");
339 
340 		/* flush FIFOs */
341 		val = (1 << M_FIFO_RX_FLUSH_SHIFT) |
342 		      (1 << M_FIFO_TX_FLUSH_SHIFT);
343 		writel(val, iproc_i2c->base + M_FIFO_CTRL_OFFSET);
344 		return -ETIMEDOUT;
345 	}
346 
347 	ret = bcm_iproc_i2c_check_status(iproc_i2c, msg);
348 	if (ret) {
349 		/* flush both TX/RX FIFOs */
350 		val = (1 << M_FIFO_RX_FLUSH_SHIFT) |
351 		      (1 << M_FIFO_TX_FLUSH_SHIFT);
352 		writel(val, iproc_i2c->base + M_FIFO_CTRL_OFFSET);
353 		return ret;
354 	}
355 
356 	/*
357 	 * For a read operation, we now need to load the data from FIFO
358 	 * into the memory buffer
359 	 */
360 	if (msg->flags & I2C_M_RD) {
361 		for (i = 0; i < msg->len; i++) {
362 			msg->buf[i] = (readl(iproc_i2c->base + M_RX_OFFSET) >>
363 				      M_RX_DATA_SHIFT) & M_RX_DATA_MASK;
364 		}
365 	}
366 
367 	return 0;
368 }
369 
370 static int bcm_iproc_i2c_xfer(struct i2c_adapter *adapter,
371 			      struct i2c_msg msgs[], int num)
372 {
373 	struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adapter);
374 	int ret, i;
375 
376 	/* go through all messages */
377 	for (i = 0; i < num; i++) {
378 		ret = bcm_iproc_i2c_xfer_single_msg(iproc_i2c, &msgs[i]);
379 		if (ret) {
380 			dev_dbg(iproc_i2c->device, "xfer failed\n");
381 			return ret;
382 		}
383 	}
384 
385 	return num;
386 }
387 
388 static uint32_t bcm_iproc_i2c_functionality(struct i2c_adapter *adap)
389 {
390 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
391 }
392 
393 static const struct i2c_algorithm bcm_iproc_algo = {
394 	.master_xfer = bcm_iproc_i2c_xfer,
395 	.functionality = bcm_iproc_i2c_functionality,
396 };
397 
398 static const struct i2c_adapter_quirks bcm_iproc_i2c_quirks = {
399 	/* need to reserve one byte in the FIFO for the slave address */
400 	.max_read_len = M_TX_RX_FIFO_SIZE - 1,
401 };
402 
403 static int bcm_iproc_i2c_cfg_speed(struct bcm_iproc_i2c_dev *iproc_i2c)
404 {
405 	unsigned int bus_speed;
406 	u32 val;
407 	int ret = of_property_read_u32(iproc_i2c->device->of_node,
408 				       "clock-frequency", &bus_speed);
409 	if (ret < 0) {
410 		dev_info(iproc_i2c->device,
411 			"unable to interpret clock-frequency DT property\n");
412 		bus_speed = 100000;
413 	}
414 
415 	if (bus_speed < 100000) {
416 		dev_err(iproc_i2c->device, "%d Hz bus speed not supported\n",
417 			bus_speed);
418 		dev_err(iproc_i2c->device,
419 			"valid speeds are 100khz and 400khz\n");
420 		return -EINVAL;
421 	} else if (bus_speed < 400000) {
422 		bus_speed = 100000;
423 	} else {
424 		bus_speed = 400000;
425 	}
426 
427 	iproc_i2c->bus_speed = bus_speed;
428 	val = readl(iproc_i2c->base + TIM_CFG_OFFSET);
429 	val &= ~(1 << TIM_CFG_MODE_400_SHIFT);
430 	val |= (bus_speed == 400000) << TIM_CFG_MODE_400_SHIFT;
431 	writel(val, iproc_i2c->base + TIM_CFG_OFFSET);
432 
433 	dev_info(iproc_i2c->device, "bus set to %u Hz\n", bus_speed);
434 
435 	return 0;
436 }
437 
438 static int bcm_iproc_i2c_probe(struct platform_device *pdev)
439 {
440 	int irq, ret = 0;
441 	struct bcm_iproc_i2c_dev *iproc_i2c;
442 	struct i2c_adapter *adap;
443 	struct resource *res;
444 
445 	iproc_i2c = devm_kzalloc(&pdev->dev, sizeof(*iproc_i2c),
446 				 GFP_KERNEL);
447 	if (!iproc_i2c)
448 		return -ENOMEM;
449 
450 	platform_set_drvdata(pdev, iproc_i2c);
451 	iproc_i2c->device = &pdev->dev;
452 	init_completion(&iproc_i2c->done);
453 
454 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
455 	iproc_i2c->base = devm_ioremap_resource(iproc_i2c->device, res);
456 	if (IS_ERR(iproc_i2c->base))
457 		return PTR_ERR(iproc_i2c->base);
458 
459 	ret = bcm_iproc_i2c_init(iproc_i2c);
460 	if (ret)
461 		return ret;
462 
463 	ret = bcm_iproc_i2c_cfg_speed(iproc_i2c);
464 	if (ret)
465 		return ret;
466 
467 	irq = platform_get_irq(pdev, 0);
468 	if (irq <= 0) {
469 		dev_err(iproc_i2c->device, "no irq resource\n");
470 		return irq;
471 	}
472 	iproc_i2c->irq = irq;
473 
474 	ret = devm_request_irq(iproc_i2c->device, irq, bcm_iproc_i2c_isr, 0,
475 			       pdev->name, iproc_i2c);
476 	if (ret < 0) {
477 		dev_err(iproc_i2c->device, "unable to request irq %i\n", irq);
478 		return ret;
479 	}
480 
481 	bcm_iproc_i2c_enable_disable(iproc_i2c, true);
482 
483 	adap = &iproc_i2c->adapter;
484 	i2c_set_adapdata(adap, iproc_i2c);
485 	strlcpy(adap->name, "Broadcom iProc I2C adapter", sizeof(adap->name));
486 	adap->algo = &bcm_iproc_algo;
487 	adap->quirks = &bcm_iproc_i2c_quirks;
488 	adap->dev.parent = &pdev->dev;
489 	adap->dev.of_node = pdev->dev.of_node;
490 
491 	return i2c_add_adapter(adap);
492 }
493 
494 static int bcm_iproc_i2c_remove(struct platform_device *pdev)
495 {
496 	struct bcm_iproc_i2c_dev *iproc_i2c = platform_get_drvdata(pdev);
497 
498 	/* make sure there's no pending interrupt when we remove the adapter */
499 	writel(0, iproc_i2c->base + IE_OFFSET);
500 	readl(iproc_i2c->base + IE_OFFSET);
501 	synchronize_irq(iproc_i2c->irq);
502 
503 	i2c_del_adapter(&iproc_i2c->adapter);
504 	bcm_iproc_i2c_enable_disable(iproc_i2c, false);
505 
506 	return 0;
507 }
508 
509 #ifdef CONFIG_PM_SLEEP
510 
511 static int bcm_iproc_i2c_suspend(struct device *dev)
512 {
513 	struct platform_device *pdev = to_platform_device(dev);
514 	struct bcm_iproc_i2c_dev *iproc_i2c = platform_get_drvdata(pdev);
515 
516 	/* make sure there's no pending interrupt when we go into suspend */
517 	writel(0, iproc_i2c->base + IE_OFFSET);
518 	readl(iproc_i2c->base + IE_OFFSET);
519 	synchronize_irq(iproc_i2c->irq);
520 
521 	/* now disable the controller */
522 	bcm_iproc_i2c_enable_disable(iproc_i2c, false);
523 
524 	return 0;
525 }
526 
527 static int bcm_iproc_i2c_resume(struct device *dev)
528 {
529 	struct platform_device *pdev = to_platform_device(dev);
530 	struct bcm_iproc_i2c_dev *iproc_i2c = platform_get_drvdata(pdev);
531 	int ret;
532 	u32 val;
533 
534 	/*
535 	 * Power domain could have been shut off completely in system deep
536 	 * sleep, so re-initialize the block here
537 	 */
538 	ret = bcm_iproc_i2c_init(iproc_i2c);
539 	if (ret)
540 		return ret;
541 
542 	/* configure to the desired bus speed */
543 	val = readl(iproc_i2c->base + TIM_CFG_OFFSET);
544 	val &= ~(1 << TIM_CFG_MODE_400_SHIFT);
545 	val |= (iproc_i2c->bus_speed == 400000) << TIM_CFG_MODE_400_SHIFT;
546 	writel(val, iproc_i2c->base + TIM_CFG_OFFSET);
547 
548 	bcm_iproc_i2c_enable_disable(iproc_i2c, true);
549 
550 	return 0;
551 }
552 
553 static const struct dev_pm_ops bcm_iproc_i2c_pm_ops = {
554 	.suspend_late = &bcm_iproc_i2c_suspend,
555 	.resume_early = &bcm_iproc_i2c_resume
556 };
557 
558 #define BCM_IPROC_I2C_PM_OPS (&bcm_iproc_i2c_pm_ops)
559 #else
560 #define BCM_IPROC_I2C_PM_OPS NULL
561 #endif /* CONFIG_PM_SLEEP */
562 
563 static const struct of_device_id bcm_iproc_i2c_of_match[] = {
564 	{ .compatible = "brcm,iproc-i2c" },
565 	{ /* sentinel */ }
566 };
567 MODULE_DEVICE_TABLE(of, bcm_iproc_i2c_of_match);
568 
569 static struct platform_driver bcm_iproc_i2c_driver = {
570 	.driver = {
571 		.name = "bcm-iproc-i2c",
572 		.of_match_table = bcm_iproc_i2c_of_match,
573 		.pm = BCM_IPROC_I2C_PM_OPS,
574 	},
575 	.probe = bcm_iproc_i2c_probe,
576 	.remove = bcm_iproc_i2c_remove,
577 };
578 module_platform_driver(bcm_iproc_i2c_driver);
579 
580 MODULE_AUTHOR("Ray Jui <rjui@broadcom.com>");
581 MODULE_DESCRIPTION("Broadcom iProc I2C Driver");
582 MODULE_LICENSE("GPL v2");
583