1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  i2c Support for Atmel's AT91 Two-Wire Interface (TWI)
4  *
5  *  Copyright (C) 2011 Weinmann Medical GmbH
6  *  Author: Nikolaus Voss <n.voss@weinmann.de>
7  *
8  *  Evolved from original work by:
9  *  Copyright (C) 2004 Rick Bronson
10  *  Converted to 2.6 by Andrew Victor <andrew@sanpeople.com>
11  *
12  *  Borrowed heavily from original work by:
13  *  Copyright (C) 2000 Philip Edelbrock <phil@stimpy.netroedge.com>
14  */
15 
16 #include <linux/clk.h>
17 #include <linux/completion.h>
18 #include <linux/dma-mapping.h>
19 #include <linux/dmaengine.h>
20 #include <linux/err.h>
21 #include <linux/gpio/consumer.h>
22 #include <linux/i2c.h>
23 #include <linux/interrupt.h>
24 #include <linux/io.h>
25 #include <linux/of.h>
26 #include <linux/of_device.h>
27 #include <linux/pinctrl/consumer.h>
28 #include <linux/platform_device.h>
29 #include <linux/pm_runtime.h>
30 
31 #include "i2c-at91.h"
32 
33 void at91_init_twi_bus_master(struct at91_twi_dev *dev)
34 {
35 	struct at91_twi_pdata *pdata = dev->pdata;
36 	u32 filtr = 0;
37 
38 	/* FIFO should be enabled immediately after the software reset */
39 	if (dev->fifo_size)
40 		at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_FIFOEN);
41 	at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_MSEN);
42 	at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SVDIS);
43 	at91_twi_write(dev, AT91_TWI_CWGR, dev->twi_cwgr_reg);
44 
45 	/* enable digital filter */
46 	if (pdata->has_dig_filtr && dev->enable_dig_filt)
47 		filtr |= AT91_TWI_FILTR_FILT;
48 
49 	/* enable advanced digital filter */
50 	if (pdata->has_adv_dig_filtr && dev->enable_dig_filt)
51 		filtr |= AT91_TWI_FILTR_FILT |
52 			 (AT91_TWI_FILTR_THRES(dev->filter_width) &
53 			 AT91_TWI_FILTR_THRES_MASK);
54 
55 	/* enable analog filter */
56 	if (pdata->has_ana_filtr && dev->enable_ana_filt)
57 		filtr |= AT91_TWI_FILTR_PADFEN;
58 
59 	if (filtr)
60 		at91_twi_write(dev, AT91_TWI_FILTR, filtr);
61 }
62 
63 /*
64  * Calculate symmetric clock as stated in datasheet:
65  * twi_clk = F_MAIN / (2 * (cdiv * (1 << ckdiv) + offset))
66  */
67 static void at91_calc_twi_clock(struct at91_twi_dev *dev)
68 {
69 	int ckdiv, cdiv, div, hold = 0, filter_width = 0;
70 	struct at91_twi_pdata *pdata = dev->pdata;
71 	int offset = pdata->clk_offset;
72 	int max_ckdiv = pdata->clk_max_div;
73 	struct i2c_timings timings, *t = &timings;
74 
75 	i2c_parse_fw_timings(dev->dev, t, true);
76 
77 	div = max(0, (int)DIV_ROUND_UP(clk_get_rate(dev->clk),
78 				       2 * t->bus_freq_hz) - offset);
79 	ckdiv = fls(div >> 8);
80 	cdiv = div >> ckdiv;
81 
82 	if (ckdiv > max_ckdiv) {
83 		dev_warn(dev->dev, "%d exceeds ckdiv max value which is %d.\n",
84 			 ckdiv, max_ckdiv);
85 		ckdiv = max_ckdiv;
86 		cdiv = 255;
87 	}
88 
89 	if (pdata->has_hold_field) {
90 		/*
91 		 * hold time = HOLD + 3 x T_peripheral_clock
92 		 * Use clk rate in kHz to prevent overflows when computing
93 		 * hold.
94 		 */
95 		hold = DIV_ROUND_UP(t->sda_hold_ns
96 				    * (clk_get_rate(dev->clk) / 1000), 1000000);
97 		hold -= 3;
98 		if (hold < 0)
99 			hold = 0;
100 		if (hold > AT91_TWI_CWGR_HOLD_MAX) {
101 			dev_warn(dev->dev,
102 				 "HOLD field set to its maximum value (%d instead of %d)\n",
103 				 AT91_TWI_CWGR_HOLD_MAX, hold);
104 			hold = AT91_TWI_CWGR_HOLD_MAX;
105 		}
106 	}
107 
108 	if (pdata->has_adv_dig_filtr) {
109 		/*
110 		 * filter width = 0 to AT91_TWI_FILTR_THRES_MAX
111 		 * peripheral clocks
112 		 */
113 		filter_width = DIV_ROUND_UP(t->digital_filter_width_ns
114 				* (clk_get_rate(dev->clk) / 1000), 1000000);
115 		if (filter_width > AT91_TWI_FILTR_THRES_MAX) {
116 			dev_warn(dev->dev,
117 				"Filter threshold set to its maximum value (%d instead of %d)\n",
118 				AT91_TWI_FILTR_THRES_MAX, filter_width);
119 			filter_width = AT91_TWI_FILTR_THRES_MAX;
120 		}
121 	}
122 
123 	dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv
124 			    | AT91_TWI_CWGR_HOLD(hold);
125 
126 	dev->filter_width = filter_width;
127 
128 	dev_dbg(dev->dev, "cdiv %d ckdiv %d hold %d (%d ns), filter_width %d (%d ns)\n",
129 		cdiv, ckdiv, hold, t->sda_hold_ns, filter_width,
130 		t->digital_filter_width_ns);
131 }
132 
133 static void at91_twi_dma_cleanup(struct at91_twi_dev *dev)
134 {
135 	struct at91_twi_dma *dma = &dev->dma;
136 
137 	at91_twi_irq_save(dev);
138 
139 	if (dma->xfer_in_progress) {
140 		if (dma->direction == DMA_FROM_DEVICE)
141 			dmaengine_terminate_sync(dma->chan_rx);
142 		else
143 			dmaengine_terminate_sync(dma->chan_tx);
144 		dma->xfer_in_progress = false;
145 	}
146 	if (dma->buf_mapped) {
147 		dma_unmap_single(dev->dev, sg_dma_address(&dma->sg[0]),
148 				 dev->buf_len, dma->direction);
149 		dma->buf_mapped = false;
150 	}
151 
152 	at91_twi_irq_restore(dev);
153 }
154 
155 static void at91_twi_write_next_byte(struct at91_twi_dev *dev)
156 {
157 	if (!dev->buf_len)
158 		return;
159 
160 	/* 8bit write works with and without FIFO */
161 	writeb_relaxed(*dev->buf, dev->base + AT91_TWI_THR);
162 
163 	/* send stop when last byte has been written */
164 	if (--dev->buf_len == 0) {
165 		if (!dev->use_alt_cmd)
166 			at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_STOP);
167 		at91_twi_write(dev, AT91_TWI_IDR, AT91_TWI_TXRDY);
168 	}
169 
170 	dev_dbg(dev->dev, "wrote 0x%x, to go %zu\n", *dev->buf, dev->buf_len);
171 
172 	++dev->buf;
173 }
174 
175 static void at91_twi_write_data_dma_callback(void *data)
176 {
177 	struct at91_twi_dev *dev = (struct at91_twi_dev *)data;
178 
179 	dma_unmap_single(dev->dev, sg_dma_address(&dev->dma.sg[0]),
180 			 dev->buf_len, DMA_TO_DEVICE);
181 
182 	/*
183 	 * When this callback is called, THR/TX FIFO is likely not to be empty
184 	 * yet. So we have to wait for TXCOMP or NACK bits to be set into the
185 	 * Status Register to be sure that the STOP bit has been sent and the
186 	 * transfer is completed. The NACK interrupt has already been enabled,
187 	 * we just have to enable TXCOMP one.
188 	 */
189 	at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_TXCOMP);
190 	if (!dev->use_alt_cmd)
191 		at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_STOP);
192 }
193 
194 static void at91_twi_write_data_dma(struct at91_twi_dev *dev)
195 {
196 	dma_addr_t dma_addr;
197 	struct dma_async_tx_descriptor *txdesc;
198 	struct at91_twi_dma *dma = &dev->dma;
199 	struct dma_chan *chan_tx = dma->chan_tx;
200 	unsigned int sg_len = 1;
201 
202 	if (!dev->buf_len)
203 		return;
204 
205 	dma->direction = DMA_TO_DEVICE;
206 
207 	at91_twi_irq_save(dev);
208 	dma_addr = dma_map_single(dev->dev, dev->buf, dev->buf_len,
209 				  DMA_TO_DEVICE);
210 	if (dma_mapping_error(dev->dev, dma_addr)) {
211 		dev_err(dev->dev, "dma map failed\n");
212 		return;
213 	}
214 	dma->buf_mapped = true;
215 	at91_twi_irq_restore(dev);
216 
217 	if (dev->fifo_size) {
218 		size_t part1_len, part2_len;
219 		struct scatterlist *sg;
220 		unsigned fifo_mr;
221 
222 		sg_len = 0;
223 
224 		part1_len = dev->buf_len & ~0x3;
225 		if (part1_len) {
226 			sg = &dma->sg[sg_len++];
227 			sg_dma_len(sg) = part1_len;
228 			sg_dma_address(sg) = dma_addr;
229 		}
230 
231 		part2_len = dev->buf_len & 0x3;
232 		if (part2_len) {
233 			sg = &dma->sg[sg_len++];
234 			sg_dma_len(sg) = part2_len;
235 			sg_dma_address(sg) = dma_addr + part1_len;
236 		}
237 
238 		/*
239 		 * DMA controller is triggered when at least 4 data can be
240 		 * written into the TX FIFO
241 		 */
242 		fifo_mr = at91_twi_read(dev, AT91_TWI_FMR);
243 		fifo_mr &= ~AT91_TWI_FMR_TXRDYM_MASK;
244 		fifo_mr |= AT91_TWI_FMR_TXRDYM(AT91_TWI_FOUR_DATA);
245 		at91_twi_write(dev, AT91_TWI_FMR, fifo_mr);
246 	} else {
247 		sg_dma_len(&dma->sg[0]) = dev->buf_len;
248 		sg_dma_address(&dma->sg[0]) = dma_addr;
249 	}
250 
251 	txdesc = dmaengine_prep_slave_sg(chan_tx, dma->sg, sg_len,
252 					 DMA_MEM_TO_DEV,
253 					 DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
254 	if (!txdesc) {
255 		dev_err(dev->dev, "dma prep slave sg failed\n");
256 		goto error;
257 	}
258 
259 	txdesc->callback = at91_twi_write_data_dma_callback;
260 	txdesc->callback_param = dev;
261 
262 	dma->xfer_in_progress = true;
263 	dmaengine_submit(txdesc);
264 	dma_async_issue_pending(chan_tx);
265 
266 	return;
267 
268 error:
269 	at91_twi_dma_cleanup(dev);
270 }
271 
272 static void at91_twi_read_next_byte(struct at91_twi_dev *dev)
273 {
274 	/*
275 	 * If we are in this case, it means there is garbage data in RHR, so
276 	 * delete them.
277 	 */
278 	if (!dev->buf_len) {
279 		at91_twi_read(dev, AT91_TWI_RHR);
280 		return;
281 	}
282 
283 	/* 8bit read works with and without FIFO */
284 	*dev->buf = readb_relaxed(dev->base + AT91_TWI_RHR);
285 	--dev->buf_len;
286 
287 	/* return if aborting, we only needed to read RHR to clear RXRDY*/
288 	if (dev->recv_len_abort)
289 		return;
290 
291 	/* handle I2C_SMBUS_BLOCK_DATA */
292 	if (unlikely(dev->msg->flags & I2C_M_RECV_LEN)) {
293 		/* ensure length byte is a valid value */
294 		if (*dev->buf <= I2C_SMBUS_BLOCK_MAX && *dev->buf > 0) {
295 			dev->msg->flags &= ~I2C_M_RECV_LEN;
296 			dev->buf_len += *dev->buf;
297 			dev->msg->len = dev->buf_len + 1;
298 			dev_dbg(dev->dev, "received block length %zu\n",
299 					 dev->buf_len);
300 		} else {
301 			/* abort and send the stop by reading one more byte */
302 			dev->recv_len_abort = true;
303 			dev->buf_len = 1;
304 		}
305 	}
306 
307 	/* send stop if second but last byte has been read */
308 	if (!dev->use_alt_cmd && dev->buf_len == 1)
309 		at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_STOP);
310 
311 	dev_dbg(dev->dev, "read 0x%x, to go %zu\n", *dev->buf, dev->buf_len);
312 
313 	++dev->buf;
314 }
315 
316 static void at91_twi_read_data_dma_callback(void *data)
317 {
318 	struct at91_twi_dev *dev = (struct at91_twi_dev *)data;
319 	unsigned ier = AT91_TWI_TXCOMP;
320 
321 	dma_unmap_single(dev->dev, sg_dma_address(&dev->dma.sg[0]),
322 			 dev->buf_len, DMA_FROM_DEVICE);
323 
324 	if (!dev->use_alt_cmd) {
325 		/* The last two bytes have to be read without using dma */
326 		dev->buf += dev->buf_len - 2;
327 		dev->buf_len = 2;
328 		ier |= AT91_TWI_RXRDY;
329 	}
330 	at91_twi_write(dev, AT91_TWI_IER, ier);
331 }
332 
333 static void at91_twi_read_data_dma(struct at91_twi_dev *dev)
334 {
335 	dma_addr_t dma_addr;
336 	struct dma_async_tx_descriptor *rxdesc;
337 	struct at91_twi_dma *dma = &dev->dma;
338 	struct dma_chan *chan_rx = dma->chan_rx;
339 	size_t buf_len;
340 
341 	buf_len = (dev->use_alt_cmd) ? dev->buf_len : dev->buf_len - 2;
342 	dma->direction = DMA_FROM_DEVICE;
343 
344 	/* Keep in mind that we won't use dma to read the last two bytes */
345 	at91_twi_irq_save(dev);
346 	dma_addr = dma_map_single(dev->dev, dev->buf, buf_len, DMA_FROM_DEVICE);
347 	if (dma_mapping_error(dev->dev, dma_addr)) {
348 		dev_err(dev->dev, "dma map failed\n");
349 		return;
350 	}
351 	dma->buf_mapped = true;
352 	at91_twi_irq_restore(dev);
353 
354 	if (dev->fifo_size && IS_ALIGNED(buf_len, 4)) {
355 		unsigned fifo_mr;
356 
357 		/*
358 		 * DMA controller is triggered when at least 4 data can be
359 		 * read from the RX FIFO
360 		 */
361 		fifo_mr = at91_twi_read(dev, AT91_TWI_FMR);
362 		fifo_mr &= ~AT91_TWI_FMR_RXRDYM_MASK;
363 		fifo_mr |= AT91_TWI_FMR_RXRDYM(AT91_TWI_FOUR_DATA);
364 		at91_twi_write(dev, AT91_TWI_FMR, fifo_mr);
365 	}
366 
367 	sg_dma_len(&dma->sg[0]) = buf_len;
368 	sg_dma_address(&dma->sg[0]) = dma_addr;
369 
370 	rxdesc = dmaengine_prep_slave_sg(chan_rx, dma->sg, 1, DMA_DEV_TO_MEM,
371 					 DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
372 	if (!rxdesc) {
373 		dev_err(dev->dev, "dma prep slave sg failed\n");
374 		goto error;
375 	}
376 
377 	rxdesc->callback = at91_twi_read_data_dma_callback;
378 	rxdesc->callback_param = dev;
379 
380 	dma->xfer_in_progress = true;
381 	dmaengine_submit(rxdesc);
382 	dma_async_issue_pending(dma->chan_rx);
383 
384 	return;
385 
386 error:
387 	at91_twi_dma_cleanup(dev);
388 }
389 
390 static irqreturn_t atmel_twi_interrupt(int irq, void *dev_id)
391 {
392 	struct at91_twi_dev *dev = dev_id;
393 	const unsigned status = at91_twi_read(dev, AT91_TWI_SR);
394 	const unsigned irqstatus = status & at91_twi_read(dev, AT91_TWI_IMR);
395 
396 	if (!irqstatus)
397 		return IRQ_NONE;
398 	/*
399 	 * In reception, the behavior of the twi device (before sama5d2) is
400 	 * weird. There is some magic about RXRDY flag! When a data has been
401 	 * almost received, the reception of a new one is anticipated if there
402 	 * is no stop command to send. That is the reason why ask for sending
403 	 * the stop command not on the last data but on the second last one.
404 	 *
405 	 * Unfortunately, we could still have the RXRDY flag set even if the
406 	 * transfer is done and we have read the last data. It might happen
407 	 * when the i2c slave device sends too quickly data after receiving the
408 	 * ack from the master. The data has been almost received before having
409 	 * the order to send stop. In this case, sending the stop command could
410 	 * cause a RXRDY interrupt with a TXCOMP one. It is better to manage
411 	 * the RXRDY interrupt first in order to not keep garbage data in the
412 	 * Receive Holding Register for the next transfer.
413 	 */
414 	if (irqstatus & AT91_TWI_RXRDY) {
415 		/*
416 		 * Read all available bytes at once by polling RXRDY usable w/
417 		 * and w/o FIFO. With FIFO enabled we could also read RXFL and
418 		 * avoid polling RXRDY.
419 		 */
420 		do {
421 			at91_twi_read_next_byte(dev);
422 		} while (at91_twi_read(dev, AT91_TWI_SR) & AT91_TWI_RXRDY);
423 	}
424 
425 	/*
426 	 * When a NACK condition is detected, the I2C controller sets the NACK,
427 	 * TXCOMP and TXRDY bits all together in the Status Register (SR).
428 	 *
429 	 * 1 - Handling NACK errors with CPU write transfer.
430 	 *
431 	 * In such case, we should not write the next byte into the Transmit
432 	 * Holding Register (THR) otherwise the I2C controller would start a new
433 	 * transfer and the I2C slave is likely to reply by another NACK.
434 	 *
435 	 * 2 - Handling NACK errors with DMA write transfer.
436 	 *
437 	 * By setting the TXRDY bit in the SR, the I2C controller also triggers
438 	 * the DMA controller to write the next data into the THR. Then the
439 	 * result depends on the hardware version of the I2C controller.
440 	 *
441 	 * 2a - Without support of the Alternative Command mode.
442 	 *
443 	 * This is the worst case: the DMA controller is triggered to write the
444 	 * next data into the THR, hence starting a new transfer: the I2C slave
445 	 * is likely to reply by another NACK.
446 	 * Concurrently, this interrupt handler is likely to be called to manage
447 	 * the first NACK before the I2C controller detects the second NACK and
448 	 * sets once again the NACK bit into the SR.
449 	 * When handling the first NACK, this interrupt handler disables the I2C
450 	 * controller interruptions, especially the NACK interrupt.
451 	 * Hence, the NACK bit is pending into the SR. This is why we should
452 	 * read the SR to clear all pending interrupts at the beginning of
453 	 * at91_do_twi_transfer() before actually starting a new transfer.
454 	 *
455 	 * 2b - With support of the Alternative Command mode.
456 	 *
457 	 * When a NACK condition is detected, the I2C controller also locks the
458 	 * THR (and sets the LOCK bit in the SR): even though the DMA controller
459 	 * is triggered by the TXRDY bit to write the next data into the THR,
460 	 * this data actually won't go on the I2C bus hence a second NACK is not
461 	 * generated.
462 	 */
463 	if (irqstatus & (AT91_TWI_TXCOMP | AT91_TWI_NACK)) {
464 		at91_disable_twi_interrupts(dev);
465 		complete(&dev->cmd_complete);
466 	} else if (irqstatus & AT91_TWI_TXRDY) {
467 		at91_twi_write_next_byte(dev);
468 	}
469 
470 	/* catch error flags */
471 	dev->transfer_status |= status;
472 
473 	return IRQ_HANDLED;
474 }
475 
476 static int at91_do_twi_transfer(struct at91_twi_dev *dev)
477 {
478 	int ret;
479 	unsigned long time_left;
480 	bool has_unre_flag = dev->pdata->has_unre_flag;
481 	bool has_alt_cmd = dev->pdata->has_alt_cmd;
482 
483 	/*
484 	 * WARNING: the TXCOMP bit in the Status Register is NOT a clear on
485 	 * read flag but shows the state of the transmission at the time the
486 	 * Status Register is read. According to the programmer datasheet,
487 	 * TXCOMP is set when both holding register and internal shifter are
488 	 * empty and STOP condition has been sent.
489 	 * Consequently, we should enable NACK interrupt rather than TXCOMP to
490 	 * detect transmission failure.
491 	 * Indeed let's take the case of an i2c write command using DMA.
492 	 * Whenever the slave doesn't acknowledge a byte, the LOCK, NACK and
493 	 * TXCOMP bits are set together into the Status Register.
494 	 * LOCK is a clear on write bit, which is set to prevent the DMA
495 	 * controller from sending new data on the i2c bus after a NACK
496 	 * condition has happened. Once locked, this i2c peripheral stops
497 	 * triggering the DMA controller for new data but it is more than
498 	 * likely that a new DMA transaction is already in progress, writing
499 	 * into the Transmit Holding Register. Since the peripheral is locked,
500 	 * these new data won't be sent to the i2c bus but they will remain
501 	 * into the Transmit Holding Register, so TXCOMP bit is cleared.
502 	 * Then when the interrupt handler is called, the Status Register is
503 	 * read: the TXCOMP bit is clear but NACK bit is still set. The driver
504 	 * manage the error properly, without waiting for timeout.
505 	 * This case can be reproduced easyly when writing into an at24 eeprom.
506 	 *
507 	 * Besides, the TXCOMP bit is already set before the i2c transaction
508 	 * has been started. For read transactions, this bit is cleared when
509 	 * writing the START bit into the Control Register. So the
510 	 * corresponding interrupt can safely be enabled just after.
511 	 * However for write transactions managed by the CPU, we first write
512 	 * into THR, so TXCOMP is cleared. Then we can safely enable TXCOMP
513 	 * interrupt. If TXCOMP interrupt were enabled before writing into THR,
514 	 * the interrupt handler would be called immediately and the i2c command
515 	 * would be reported as completed.
516 	 * Also when a write transaction is managed by the DMA controller,
517 	 * enabling the TXCOMP interrupt in this function may lead to a race
518 	 * condition since we don't know whether the TXCOMP interrupt is enabled
519 	 * before or after the DMA has started to write into THR. So the TXCOMP
520 	 * interrupt is enabled later by at91_twi_write_data_dma_callback().
521 	 * Immediately after in that DMA callback, if the alternative command
522 	 * mode is not used, we still need to send the STOP condition manually
523 	 * writing the corresponding bit into the Control Register.
524 	 */
525 
526 	dev_dbg(dev->dev, "transfer: %s %zu bytes.\n",
527 		(dev->msg->flags & I2C_M_RD) ? "read" : "write", dev->buf_len);
528 
529 	reinit_completion(&dev->cmd_complete);
530 	dev->transfer_status = 0;
531 
532 	/* Clear pending interrupts, such as NACK. */
533 	at91_twi_read(dev, AT91_TWI_SR);
534 
535 	if (dev->fifo_size) {
536 		unsigned fifo_mr = at91_twi_read(dev, AT91_TWI_FMR);
537 
538 		/* Reset FIFO mode register */
539 		fifo_mr &= ~(AT91_TWI_FMR_TXRDYM_MASK |
540 			     AT91_TWI_FMR_RXRDYM_MASK);
541 		fifo_mr |= AT91_TWI_FMR_TXRDYM(AT91_TWI_ONE_DATA);
542 		fifo_mr |= AT91_TWI_FMR_RXRDYM(AT91_TWI_ONE_DATA);
543 		at91_twi_write(dev, AT91_TWI_FMR, fifo_mr);
544 
545 		/* Flush FIFOs */
546 		at91_twi_write(dev, AT91_TWI_CR,
547 			       AT91_TWI_THRCLR | AT91_TWI_RHRCLR);
548 	}
549 
550 	if (!dev->buf_len) {
551 		at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_QUICK);
552 		at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_TXCOMP);
553 	} else if (dev->msg->flags & I2C_M_RD) {
554 		unsigned start_flags = AT91_TWI_START;
555 
556 		/* if only one byte is to be read, immediately stop transfer */
557 		if (!dev->use_alt_cmd && dev->buf_len <= 1 &&
558 		    !(dev->msg->flags & I2C_M_RECV_LEN))
559 			start_flags |= AT91_TWI_STOP;
560 		at91_twi_write(dev, AT91_TWI_CR, start_flags);
561 		/*
562 		 * When using dma without alternative command mode, the last
563 		 * byte has to be read manually in order to not send the stop
564 		 * command too late and then to receive extra data.
565 		 * In practice, there are some issues if you use the dma to
566 		 * read n-1 bytes because of latency.
567 		 * Reading n-2 bytes with dma and the two last ones manually
568 		 * seems to be the best solution.
569 		 */
570 		if (dev->use_dma && (dev->buf_len > AT91_I2C_DMA_THRESHOLD)) {
571 			at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_NACK);
572 			at91_twi_read_data_dma(dev);
573 		} else {
574 			at91_twi_write(dev, AT91_TWI_IER,
575 				       AT91_TWI_TXCOMP |
576 				       AT91_TWI_NACK |
577 				       AT91_TWI_RXRDY);
578 		}
579 	} else {
580 		if (dev->use_dma && (dev->buf_len > AT91_I2C_DMA_THRESHOLD)) {
581 			at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_NACK);
582 			at91_twi_write_data_dma(dev);
583 		} else {
584 			at91_twi_write_next_byte(dev);
585 			at91_twi_write(dev, AT91_TWI_IER,
586 				       AT91_TWI_TXCOMP | AT91_TWI_NACK |
587 				       (dev->buf_len ? AT91_TWI_TXRDY : 0));
588 		}
589 	}
590 
591 	time_left = wait_for_completion_timeout(&dev->cmd_complete,
592 					      dev->adapter.timeout);
593 	if (time_left == 0) {
594 		dev->transfer_status |= at91_twi_read(dev, AT91_TWI_SR);
595 		dev_err(dev->dev, "controller timed out\n");
596 		at91_init_twi_bus(dev);
597 		ret = -ETIMEDOUT;
598 		goto error;
599 	}
600 	if (dev->transfer_status & AT91_TWI_NACK) {
601 		dev_dbg(dev->dev, "received nack\n");
602 		ret = -EREMOTEIO;
603 		goto error;
604 	}
605 	if (dev->transfer_status & AT91_TWI_OVRE) {
606 		dev_err(dev->dev, "overrun while reading\n");
607 		ret = -EIO;
608 		goto error;
609 	}
610 	if (has_unre_flag && dev->transfer_status & AT91_TWI_UNRE) {
611 		dev_err(dev->dev, "underrun while writing\n");
612 		ret = -EIO;
613 		goto error;
614 	}
615 	if ((has_alt_cmd || dev->fifo_size) &&
616 	    (dev->transfer_status & AT91_TWI_LOCK)) {
617 		dev_err(dev->dev, "tx locked\n");
618 		ret = -EIO;
619 		goto error;
620 	}
621 	if (dev->recv_len_abort) {
622 		dev_err(dev->dev, "invalid smbus block length recvd\n");
623 		ret = -EPROTO;
624 		goto error;
625 	}
626 
627 	dev_dbg(dev->dev, "transfer complete\n");
628 
629 	return 0;
630 
631 error:
632 	/* first stop DMA transfer if still in progress */
633 	at91_twi_dma_cleanup(dev);
634 	/* then flush THR/FIFO and unlock TX if locked */
635 	if ((has_alt_cmd || dev->fifo_size) &&
636 	    (dev->transfer_status & AT91_TWI_LOCK)) {
637 		dev_dbg(dev->dev, "unlock tx\n");
638 		at91_twi_write(dev, AT91_TWI_CR,
639 			       AT91_TWI_THRCLR | AT91_TWI_LOCKCLR);
640 	}
641 
642 	/*
643 	 * some faulty I2C slave devices might hold SDA down;
644 	 * we can send a bus clear command, hoping that the pins will be
645 	 * released
646 	 */
647 	i2c_recover_bus(&dev->adapter);
648 
649 	return ret;
650 }
651 
652 static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)
653 {
654 	struct at91_twi_dev *dev = i2c_get_adapdata(adap);
655 	int ret;
656 	unsigned int_addr_flag = 0;
657 	struct i2c_msg *m_start = msg;
658 	bool is_read;
659 
660 	dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
661 
662 	ret = pm_runtime_get_sync(dev->dev);
663 	if (ret < 0)
664 		goto out;
665 
666 	if (num == 2) {
667 		int internal_address = 0;
668 		int i;
669 
670 		/* 1st msg is put into the internal address, start with 2nd */
671 		m_start = &msg[1];
672 		for (i = 0; i < msg->len; ++i) {
673 			const unsigned addr = msg->buf[msg->len - 1 - i];
674 
675 			internal_address |= addr << (8 * i);
676 			int_addr_flag += AT91_TWI_IADRSZ_1;
677 		}
678 		at91_twi_write(dev, AT91_TWI_IADR, internal_address);
679 	}
680 
681 	dev->use_alt_cmd = false;
682 	is_read = (m_start->flags & I2C_M_RD);
683 	if (dev->pdata->has_alt_cmd) {
684 		if (m_start->len > 0 &&
685 		    m_start->len < AT91_I2C_MAX_ALT_CMD_DATA_SIZE) {
686 			at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_ACMEN);
687 			at91_twi_write(dev, AT91_TWI_ACR,
688 				       AT91_TWI_ACR_DATAL(m_start->len) |
689 				       ((is_read) ? AT91_TWI_ACR_DIR : 0));
690 			dev->use_alt_cmd = true;
691 		} else {
692 			at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_ACMDIS);
693 		}
694 	}
695 
696 	at91_twi_write(dev, AT91_TWI_MMR,
697 		       (m_start->addr << 16) |
698 		       int_addr_flag |
699 		       ((!dev->use_alt_cmd && is_read) ? AT91_TWI_MREAD : 0));
700 
701 	dev->buf_len = m_start->len;
702 	dev->buf = m_start->buf;
703 	dev->msg = m_start;
704 	dev->recv_len_abort = false;
705 
706 	ret = at91_do_twi_transfer(dev);
707 
708 	ret = (ret < 0) ? ret : num;
709 out:
710 	pm_runtime_mark_last_busy(dev->dev);
711 	pm_runtime_put_autosuspend(dev->dev);
712 
713 	return ret;
714 }
715 
716 /*
717  * The hardware can handle at most two messages concatenated by a
718  * repeated start via it's internal address feature.
719  */
720 static const struct i2c_adapter_quirks at91_twi_quirks = {
721 	.flags = I2C_AQ_COMB | I2C_AQ_COMB_WRITE_FIRST | I2C_AQ_COMB_SAME_ADDR,
722 	.max_comb_1st_msg_len = 3,
723 };
724 
725 static u32 at91_twi_func(struct i2c_adapter *adapter)
726 {
727 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
728 		| I2C_FUNC_SMBUS_READ_BLOCK_DATA;
729 }
730 
731 static const struct i2c_algorithm at91_twi_algorithm = {
732 	.master_xfer	= at91_twi_xfer,
733 	.functionality	= at91_twi_func,
734 };
735 
736 static int at91_twi_configure_dma(struct at91_twi_dev *dev, u32 phy_addr)
737 {
738 	int ret = 0;
739 	struct dma_slave_config slave_config;
740 	struct at91_twi_dma *dma = &dev->dma;
741 	enum dma_slave_buswidth addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
742 
743 	/*
744 	 * The actual width of the access will be chosen in
745 	 * dmaengine_prep_slave_sg():
746 	 * for each buffer in the scatter-gather list, if its size is aligned
747 	 * to addr_width then addr_width accesses will be performed to transfer
748 	 * the buffer. On the other hand, if the buffer size is not aligned to
749 	 * addr_width then the buffer is transferred using single byte accesses.
750 	 * Please refer to the Atmel eXtended DMA controller driver.
751 	 * When FIFOs are used, the TXRDYM threshold can always be set to
752 	 * trigger the XDMAC when at least 4 data can be written into the TX
753 	 * FIFO, even if single byte accesses are performed.
754 	 * However the RXRDYM threshold must be set to fit the access width,
755 	 * deduced from buffer length, so the XDMAC is triggered properly to
756 	 * read data from the RX FIFO.
757 	 */
758 	if (dev->fifo_size)
759 		addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
760 
761 	memset(&slave_config, 0, sizeof(slave_config));
762 	slave_config.src_addr = (dma_addr_t)phy_addr + AT91_TWI_RHR;
763 	slave_config.src_addr_width = addr_width;
764 	slave_config.src_maxburst = 1;
765 	slave_config.dst_addr = (dma_addr_t)phy_addr + AT91_TWI_THR;
766 	slave_config.dst_addr_width = addr_width;
767 	slave_config.dst_maxburst = 1;
768 	slave_config.device_fc = false;
769 
770 	dma->chan_tx = dma_request_chan(dev->dev, "tx");
771 	if (IS_ERR(dma->chan_tx)) {
772 		ret = PTR_ERR(dma->chan_tx);
773 		dma->chan_tx = NULL;
774 		goto error;
775 	}
776 
777 	dma->chan_rx = dma_request_chan(dev->dev, "rx");
778 	if (IS_ERR(dma->chan_rx)) {
779 		ret = PTR_ERR(dma->chan_rx);
780 		dma->chan_rx = NULL;
781 		goto error;
782 	}
783 
784 	slave_config.direction = DMA_MEM_TO_DEV;
785 	if (dmaengine_slave_config(dma->chan_tx, &slave_config)) {
786 		dev_err(dev->dev, "failed to configure tx channel\n");
787 		ret = -EINVAL;
788 		goto error;
789 	}
790 
791 	slave_config.direction = DMA_DEV_TO_MEM;
792 	if (dmaengine_slave_config(dma->chan_rx, &slave_config)) {
793 		dev_err(dev->dev, "failed to configure rx channel\n");
794 		ret = -EINVAL;
795 		goto error;
796 	}
797 
798 	sg_init_table(dma->sg, 2);
799 	dma->buf_mapped = false;
800 	dma->xfer_in_progress = false;
801 	dev->use_dma = true;
802 
803 	dev_info(dev->dev, "using %s (tx) and %s (rx) for DMA transfers\n",
804 		 dma_chan_name(dma->chan_tx), dma_chan_name(dma->chan_rx));
805 
806 	return ret;
807 
808 error:
809 	if (ret != -EPROBE_DEFER)
810 		dev_info(dev->dev, "can't get DMA channel, continue without DMA support\n");
811 	if (dma->chan_rx)
812 		dma_release_channel(dma->chan_rx);
813 	if (dma->chan_tx)
814 		dma_release_channel(dma->chan_tx);
815 	return ret;
816 }
817 
818 static int at91_init_twi_recovery_gpio(struct platform_device *pdev,
819 				       struct at91_twi_dev *dev)
820 {
821 	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
822 
823 	rinfo->pinctrl = devm_pinctrl_get(&pdev->dev);
824 	if (!rinfo->pinctrl || IS_ERR(rinfo->pinctrl)) {
825 		dev_info(dev->dev, "can't get pinctrl, bus recovery not supported\n");
826 		return PTR_ERR(rinfo->pinctrl);
827 	}
828 	dev->adapter.bus_recovery_info = rinfo;
829 
830 	return 0;
831 }
832 
833 static int at91_twi_recover_bus_cmd(struct i2c_adapter *adap)
834 {
835 	struct at91_twi_dev *dev = i2c_get_adapdata(adap);
836 
837 	dev->transfer_status |= at91_twi_read(dev, AT91_TWI_SR);
838 	if (!(dev->transfer_status & AT91_TWI_SDA)) {
839 		dev_dbg(dev->dev, "SDA is down; sending bus clear command\n");
840 		if (dev->use_alt_cmd) {
841 			unsigned int acr;
842 
843 			acr = at91_twi_read(dev, AT91_TWI_ACR);
844 			acr &= ~AT91_TWI_ACR_DATAL_MASK;
845 			at91_twi_write(dev, AT91_TWI_ACR, acr);
846 		}
847 		at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_CLEAR);
848 	}
849 
850 	return 0;
851 }
852 
853 static int at91_init_twi_recovery_info(struct platform_device *pdev,
854 				       struct at91_twi_dev *dev)
855 {
856 	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
857 	bool has_clear_cmd = dev->pdata->has_clear_cmd;
858 
859 	if (!has_clear_cmd)
860 		return at91_init_twi_recovery_gpio(pdev, dev);
861 
862 	rinfo->recover_bus = at91_twi_recover_bus_cmd;
863 	dev->adapter.bus_recovery_info = rinfo;
864 
865 	return 0;
866 }
867 
868 int at91_twi_probe_master(struct platform_device *pdev,
869 			  u32 phy_addr, struct at91_twi_dev *dev)
870 {
871 	int rc;
872 
873 	init_completion(&dev->cmd_complete);
874 
875 	rc = devm_request_irq(&pdev->dev, dev->irq, atmel_twi_interrupt, 0,
876 			      dev_name(dev->dev), dev);
877 	if (rc) {
878 		dev_err(dev->dev, "Cannot get irq %d: %d\n", dev->irq, rc);
879 		return rc;
880 	}
881 
882 	if (dev->dev->of_node) {
883 		rc = at91_twi_configure_dma(dev, phy_addr);
884 		if (rc == -EPROBE_DEFER)
885 			return rc;
886 	}
887 
888 	if (!of_property_read_u32(pdev->dev.of_node, "atmel,fifo-size",
889 				  &dev->fifo_size)) {
890 		dev_info(dev->dev, "Using FIFO (%u data)\n", dev->fifo_size);
891 	}
892 
893 	dev->enable_dig_filt = of_property_read_bool(pdev->dev.of_node,
894 						     "i2c-digital-filter");
895 
896 	dev->enable_ana_filt = of_property_read_bool(pdev->dev.of_node,
897 						     "i2c-analog-filter");
898 	at91_calc_twi_clock(dev);
899 
900 	rc = at91_init_twi_recovery_info(pdev, dev);
901 	if (rc == -EPROBE_DEFER)
902 		return rc;
903 
904 	dev->adapter.algo = &at91_twi_algorithm;
905 	dev->adapter.quirks = &at91_twi_quirks;
906 
907 	return 0;
908 }
909