summaryrefslogtreecommitdiffstats
path: root/drivers/gpu/drm/drm_dp_helper.c
blob: 79968e39c8d09909395c5ad40165d0062c8227ac (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
/*
 * Copyright © 2009 Keith Packard
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting documentation, and
 * that the name of the copyright holders not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  The copyright holders make no representations
 * about the suitability of this software for any purpose.  It is provided "as
 * is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/i2c.h>
#include <drm/drm_dp_helper.h>
#include <drm/drmP.h>

/**
 * DOC: dp helpers
 *
 * These functions contain some common logic and helpers at various abstraction
 * levels to deal with Display Port sink devices and related things like DP aux
 * channel transfers, EDID reading over DP aux channels, decoding certain DPCD
 * blocks, ...
 */

/* Helpers for DP link training */
static u8 dp_link_status(const u8 link_status[DP_LINK_STATUS_SIZE], int r)
{
	return link_status[r - DP_LANE0_1_STATUS];
}

static u8 dp_get_lane_status(const u8 link_status[DP_LINK_STATUS_SIZE],
			     int lane)
{
	int i = DP_LANE0_1_STATUS + (lane >> 1);
	int s = (lane & 1) * 4;
	u8 l = dp_link_status(link_status, i);
	return (l >> s) & 0xf;
}

bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
			  int lane_count)
{
	u8 lane_align;
	u8 lane_status;
	int lane;

	lane_align = dp_link_status(link_status,
				    DP_LANE_ALIGN_STATUS_UPDATED);
	if ((lane_align & DP_INTERLANE_ALIGN_DONE) == 0)
		return false;
	for (lane = 0; lane < lane_count; lane++) {
		lane_status = dp_get_lane_status(link_status, lane);
		if ((lane_status & DP_CHANNEL_EQ_BITS) != DP_CHANNEL_EQ_BITS)
			return false;
	}
	return true;
}
EXPORT_SYMBOL(drm_dp_channel_eq_ok);

bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
			      int lane_count)
{
	int lane;
	u8 lane_status;

	for (lane = 0; lane < lane_count; lane++) {
		lane_status = dp_get_lane_status(link_status, lane);
		if ((lane_status & DP_LANE_CR_DONE) == 0)
			return false;
	}
	return true;
}
EXPORT_SYMBOL(drm_dp_clock_recovery_ok);

u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE],
				     int lane)
{
	int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
	int s = ((lane & 1) ?
		 DP_ADJUST_VOLTAGE_SWING_LANE1_SHIFT :
		 DP_ADJUST_VOLTAGE_SWING_LANE0_SHIFT);
	u8 l = dp_link_status(link_status, i);

	return ((l >> s) & 0x3) << DP_TRAIN_VOLTAGE_SWING_SHIFT;
}
EXPORT_SYMBOL(drm_dp_get_adjust_request_voltage);

u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE],
					  int lane)
{
	int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
	int s = ((lane & 1) ?
		 DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT :
		 DP_ADJUST_PRE_EMPHASIS_LANE0_SHIFT);
	u8 l = dp_link_status(link_status, i);

	return ((l >> s) & 0x3) << DP_TRAIN_PRE_EMPHASIS_SHIFT;
}
EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);

void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
	if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
		udelay(100);
	else
		mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
}
EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay);

void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
	if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
		udelay(400);
	else
		mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
}
EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);

u8 drm_dp_link_rate_to_bw_code(int link_rate)
{
	switch (link_rate) {
	case 162000:
	default:
		return DP_LINK_BW_1_62;
	case 270000:
		return DP_LINK_BW_2_7;
	case 540000:
		return DP_LINK_BW_5_4;
	}
}
EXPORT_SYMBOL(drm_dp_link_rate_to_bw_code);

int drm_dp_bw_code_to_link_rate(u8 link_bw)
{
	switch (link_bw) {
	case DP_LINK_BW_1_62:
	default:
		return 162000;
	case DP_LINK_BW_2_7:
		return 270000;
	case DP_LINK_BW_5_4:
		return 540000;
	}
}
EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);

/**
 * DOC: dp helpers
 *
 * The DisplayPort AUX channel is an abstraction to allow generic, driver-
 * independent access to AUX functionality. Drivers can take advantage of
 * this by filling in the fields of the drm_dp_aux structure.
 *
 * Transactions are described using a hardware-independent drm_dp_aux_msg
 * structure, which is passed into a driver's .transfer() implementation.
 * Both native and I2C-over-AUX transactions are supported.
 */

static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
			      unsigned int offset, void *buffer, size_t size)
{
	struct drm_dp_aux_msg msg;
	unsigned int retry;
	int err;

	memset(&msg, 0, sizeof(msg));
	msg.address = offset;
	msg.request = request;
	msg.buffer = buffer;
	msg.size = size;

	/*
	 * The specification doesn't give any recommendation on how often to
	 * retry native transactions. We used to retry 7 times like for
	 * aux i2c transactions but real world devices this wasn't
	 * sufficient, bump to 32 which makes Dell 4k monitors happier.
	 */
	for (retry = 0; retry < 32; retry++) {

		mutex_lock(&aux->hw_mutex);
		err = aux->transfer(aux, &msg);
		mutex_unlock(&aux->hw_mutex);
		if (err < 0) {
			if (err == -EBUSY)
				continue;

			return err;
		}


		switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) {
		case DP_AUX_NATIVE_REPLY_ACK:
			if (err < size)
				return -EPROTO;
			return err;

		case DP_AUX_NATIVE_REPLY_NACK:
			return -EIO;

		case DP_AUX_NATIVE_REPLY_DEFER:
			usleep_range(400, 500);
			break;
		}
	}

	DRM_DEBUG_KMS("too many retries, giving up\n");
	return -EIO;
}

/**
 * drm_dp_dpcd_read() - read a series of bytes from the DPCD
 * @aux: DisplayPort AUX channel
 * @offset: address of the (first) register to read
 * @buffer: buffer to store the register values
 * @size: number of bytes in @buffer
 *
 * Returns the number of bytes transferred on success, or a negative error
 * code on failure. -EIO is returned if the request was NAKed by the sink or
 * if the retry count was exceeded. If not all bytes were transferred, this
 * function returns -EPROTO. Errors from the underlying AUX channel transfer
 * function, with the exception of -EBUSY (which causes the transaction to
 * be retried), are propagated to the caller.
 */
ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
			 void *buffer, size_t size)
{
	return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
				  size);
}
EXPORT_SYMBOL(drm_dp_dpcd_read);

/**
 * drm_dp_dpcd_write() - write a series of bytes to the DPCD
 * @aux: DisplayPort AUX channel
 * @offset: address of the (first) register to write
 * @buffer: buffer containing the values to write
 * @size: number of bytes in @buffer
 *
 * Returns the number of bytes transferred on success, or a negative error
 * code on failure. -EIO is returned if the request was NAKed by the sink or
 * if the retry count was exceeded. If not all bytes were transferred, this
 * function returns -EPROTO. Errors from the underlying AUX channel transfer
 * function, with the exception of -EBUSY (which causes the transaction to
 * be retried), are propagated to the caller.
 */
ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
			  void *buffer, size_t size)
{
	return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,
				  size);
}
EXPORT_SYMBOL(drm_dp_dpcd_write);

/**
 * drm_dp_dpcd_read_link_status() - read DPCD link status (bytes 0x202-0x207)
 * @aux: DisplayPort AUX channel
 * @status: buffer to store the link status in (must be at least 6 bytes)
 *
 * Returns the number of bytes transferred on success or a negative error
 * code on failure.
 */
int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
				 u8 status[DP_LINK_STATUS_SIZE])
{
	return drm_dp_dpcd_read(aux, DP_LANE0_1_STATUS, status,
				DP_LINK_STATUS_SIZE);
}
EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);

/**
 * drm_dp_link_probe() - probe a DisplayPort link for capabilities
 * @aux: DisplayPort AUX channel
 * @link: pointer to structure in which to return link capabilities
 *
 * The structure filled in by this function can usually be passed directly
 * into drm_dp_link_power_up() and drm_dp_link_configure() to power up and
 * configure the link based on the link's capabilities.
 *
 * Returns 0 on success or a negative error code on failure.
 */
int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
{
	u8 values[3];
	int err;

	memset(link, 0, sizeof(*link));

	err = drm_dp_dpcd_read(aux, DP_DPCD_REV, values, sizeof(values));
	if (err < 0)
		return err;

	link->revision = values[0];
	link->rate = drm_dp_bw_code_to_link_rate(values[1]);
	link->num_lanes = values[2] & DP_MAX_LANE_COUNT_MASK;

	if (values[2] & DP_ENHANCED_FRAME_CAP)
		link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING;

	return 0;
}
EXPORT_SYMBOL(drm_dp_link_probe);

/**
 * drm_dp_link_power_up() - power up a DisplayPort link
 * @aux: DisplayPort AUX channel
 * @link: pointer to a structure containing the link configuration
 *
 * Returns 0 on success or a negative error code on failure.
 */
int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link)
{
	u8 value;
	int err;

	/* DP_SET_POWER register is only available on DPCD v1.1 and later */
	if (link->revision < 0x11)
		return 0;

	err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
	if (err < 0)
		return err;

	value &= ~DP_SET_POWER_MASK;
	value |= DP_SET_POWER_D0;

	err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
	if (err < 0)
		return err;

	/*
	 * According to the DP 1.1 specification, a "Sink Device must exit the
	 * power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink
	 * Control Field" (register 0x600).
	 */
	usleep_range(1000, 2000);

	return 0;
}
EXPORT_SYMBOL(drm_dp_link_power_up);

/**
 * drm_dp_link_configure() - configure a DisplayPort link
 * @aux: DisplayPort AUX channel
 * @link: pointer to a structure containing the link configuration
 *
 * Returns 0 on success or a negative error code on failure.
 */
int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link)
{
	u8 values[2];
	int err;

	values[0] = drm_dp_link_rate_to_bw_code(link->rate);
	values[1] = link->num_lanes;

	if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING)
		values[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;

	err = drm_dp_dpcd_write(aux, DP_LINK_BW_SET, values, sizeof(values));
	if (err < 0)
		return err;

	return 0;
}
EXPORT_SYMBOL(drm_dp_link_configure);

/*
 * I2C-over-AUX implementation
 */

static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
	       I2C_FUNC_SMBUS_READ_BLOCK_DATA |
	       I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
	       I2C_FUNC_10BIT_ADDR;
}

/*
 * Transfer a single I2C-over-AUX message and handle various error conditions,
 * retrying the transaction as appropriate.  It is assumed that the
 * aux->transfer function does not modify anything in the msg other than the
 * reply field.
 */
static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
{
	unsigned int retry;
	int err;

	/*
	 * DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device
	 * is required to retry at least seven times upon receiving AUX_DEFER
	 * before giving up the AUX transaction.
	 */
	for (retry = 0; retry < 7; retry++) {
		mutex_lock(&aux->hw_mutex);
		err = aux->transfer(aux, msg);
		mutex_unlock(&aux->hw_mutex);
		if (err < 0) {
			if (err == -EBUSY)
				continue;

			DRM_DEBUG_KMS("transaction failed: %d\n", err);
			return err;
		}


		switch (msg->reply & DP_AUX_NATIVE_REPLY_MASK) {
		case DP_AUX_NATIVE_REPLY_ACK:
			/*
			 * For I2C-over-AUX transactions this isn't enough, we
			 * need to check for the I2C ACK reply.
			 */
			break;

		case DP_AUX_NATIVE_REPLY_NACK:
			DRM_DEBUG_KMS("native nack\n");
			return -EREMOTEIO;

		case DP_AUX_NATIVE_REPLY_DEFER:
			DRM_DEBUG_KMS("native defer");
			/*
			 * We could check for I2C bit rate capabilities and if
			 * available adjust this interval. We could also be
			 * more careful with DP-to-legacy adapters where a
			 * long legacy cable may force very low I2C bit rates.
			 *
			 * For now just defer for long enough to hopefully be
			 * safe for all use-cases.
			 */
			usleep_range(500, 600);
			continue;

		default:
			DRM_ERROR("invalid native reply %#04x\n", msg->reply);
			return -EREMOTEIO;
		}

		switch (msg->reply & DP_AUX_I2C_REPLY_MASK) {
		case DP_AUX_I2C_REPLY_ACK:
			/*
			 * Both native ACK and I2C ACK replies received. We
			 * can assume the transfer was successful.
			 */
			if (err < msg->size)
				return -EPROTO;
			return 0;

		case DP_AUX_I2C_REPLY_NACK:
			DRM_DEBUG_KMS("I2C nack\n");
			aux->i2c_nack_count++;
			return -EREMOTEIO;

		case DP_AUX_I2C_REPLY_DEFER:
			DRM_DEBUG_KMS("I2C defer\n");
			aux->i2c_defer_count++;
			usleep_range(400, 500);
			continue;

		default:
			DRM_ERROR("invalid I2C reply %#04x\n", msg->reply);
			return -EREMOTEIO;
		}
	}

	DRM_DEBUG_KMS("too many retries, giving up\n");
	return -EREMOTEIO;
}

static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
			   int num)
{
	struct drm_dp_aux *aux = adapter->algo_data;
	unsigned int i, j;
	struct drm_dp_aux_msg msg;
	int err = 0;

	memset(&msg, 0, sizeof(msg));

	for (i = 0; i < num; i++) {
		msg.address = msgs[i].addr;
		msg.request = (msgs[i].flags & I2C_M_RD) ?
			DP_AUX_I2C_READ :
			DP_AUX_I2C_WRITE;
		msg.request |= DP_AUX_I2C_MOT;
		/* Send a bare address packet to start the transaction.
		 * Zero sized messages specify an address only (bare
		 * address) transaction.
		 */
		msg.buffer = NULL;
		msg.size = 0;
		err = drm_dp_i2c_do_msg(aux, &msg);
		if (err < 0)
			break;
		/*
		 * Many hardware implementations support FIFOs larger than a
		 * single byte, but it has been empirically determined that
		 * transferring data in larger chunks can actually lead to
		 * decreased performance. Therefore each message is simply
		 * transferred byte-by-byte.
		 */
		for (j = 0; j < msgs[i].len; j++) {
			msg.buffer = msgs[i].buf + j;
			msg.size = 1;

			err = drm_dp_i2c_do_msg(aux, &msg);
			if (err < 0)
				break;
		}
		if (err < 0)
			break;
	}
	if (err >= 0)
		err = num;
	/* Send a bare address packet to close out the transaction.
	 * Zero sized messages specify an address only (bare
	 * address) transaction.
	 */
	msg.request &= ~DP_AUX_I2C_MOT;
	msg.buffer = NULL;
	msg.size = 0;
	(void)drm_dp_i2c_do_msg(aux, &msg);

	return err;
}

static const struct i2c_algorithm drm_dp_i2c_algo = {
	.functionality = drm_dp_i2c_functionality,
	.master_xfer = drm_dp_i2c_xfer,
};

/**
 * drm_dp_aux_register() - initialise and register aux channel
 * @aux: DisplayPort AUX channel
 *
 * Returns 0 on success or a negative error code on failure.
 */
int drm_dp_aux_register(struct drm_dp_aux *aux)
{
	mutex_init(&aux->hw_mutex);

	aux->ddc.algo = &drm_dp_i2c_algo;
	aux->ddc.algo_data = aux;
	aux->ddc.retries = 3;

	aux->ddc.class = I2C_CLASS_DDC;
	aux->ddc.owner = THIS_MODULE;
	aux->ddc.dev.parent = aux->dev;
	aux->ddc.dev.of_node = aux->dev->of_node;

	strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev),
		sizeof(aux->ddc.name));

	return i2c_add_adapter(&aux->ddc);
}
EXPORT_SYMBOL(drm_dp_aux_register);

/**
 * drm_dp_aux_unregister() - unregister an AUX adapter
 * @aux: DisplayPort AUX channel
 */
void drm_dp_aux_unregister(struct drm_dp_aux *aux)
{
	i2c_del_adapter(&aux->ddc);
}
EXPORT_SYMBOL(drm_dp_aux_unregister);