1 // SPDX-License-Identifier: MIT 2 /* 3 * Copyright (C) 2013-2019 NVIDIA Corporation 4 * Copyright (C) 2015 Rob Clark 5 */ 6 7 #include <drm/drm_crtc.h> 8 #include <drm/drm_dp_helper.h> 9 #include <drm/drm_print.h> 10 11 #include "dp.h" 12 13 static const u8 drm_dp_edp_revisions[] = { 0x11, 0x12, 0x13, 0x14 }; 14 15 static void drm_dp_link_caps_reset(struct drm_dp_link_caps *caps) 16 { 17 caps->enhanced_framing = false; 18 caps->tps3_supported = false; 19 caps->fast_training = false; 20 caps->channel_coding = false; 21 caps->alternate_scrambler_reset = false; 22 } 23 24 void drm_dp_link_caps_copy(struct drm_dp_link_caps *dest, 25 const struct drm_dp_link_caps *src) 26 { 27 dest->enhanced_framing = src->enhanced_framing; 28 dest->tps3_supported = src->tps3_supported; 29 dest->fast_training = src->fast_training; 30 dest->channel_coding = src->channel_coding; 31 dest->alternate_scrambler_reset = src->alternate_scrambler_reset; 32 } 33 34 static void drm_dp_link_reset(struct drm_dp_link *link) 35 { 36 unsigned int i; 37 38 if (!link) 39 return; 40 41 link->revision = 0; 42 link->max_rate = 0; 43 link->max_lanes = 0; 44 45 drm_dp_link_caps_reset(&link->caps); 46 link->aux_rd_interval.cr = 0; 47 link->aux_rd_interval.ce = 0; 48 link->edp = 0; 49 50 link->rate = 0; 51 link->lanes = 0; 52 53 for (i = 0; i < DP_MAX_SUPPORTED_RATES; i++) 54 link->rates[i] = 0; 55 56 link->num_rates = 0; 57 } 58 59 /** 60 * drm_dp_link_add_rate() - add a rate to the list of supported rates 61 * @link: the link to add the rate to 62 * @rate: the rate to add 63 * 64 * Add a link rate to the list of supported link rates. 65 * 66 * Returns: 67 * 0 on success or one of the following negative error codes on failure: 68 * - ENOSPC if the maximum number of supported rates has been reached 69 * - EEXISTS if the link already supports this rate 70 * 71 * See also: 72 * drm_dp_link_remove_rate() 73 */ 74 int drm_dp_link_add_rate(struct drm_dp_link *link, unsigned long rate) 75 { 76 unsigned int i, pivot; 77 78 if (link->num_rates == DP_MAX_SUPPORTED_RATES) 79 return -ENOSPC; 80 81 for (pivot = 0; pivot < link->num_rates; pivot++) 82 if (rate <= link->rates[pivot]) 83 break; 84 85 if (pivot != link->num_rates && rate == link->rates[pivot]) 86 return -EEXIST; 87 88 for (i = link->num_rates; i > pivot; i--) 89 link->rates[i] = link->rates[i - 1]; 90 91 link->rates[pivot] = rate; 92 link->num_rates++; 93 94 return 0; 95 } 96 97 /** 98 * drm_dp_link_remove_rate() - remove a rate from the list of supported rates 99 * @link: the link from which to remove the rate 100 * @rate: the rate to remove 101 * 102 * Removes a link rate from the list of supported link rates. 103 * 104 * Returns: 105 * 0 on success or one of the following negative error codes on failure: 106 * - EINVAL if the specified rate is not among the supported rates 107 * 108 * See also: 109 * drm_dp_link_add_rate() 110 */ 111 int drm_dp_link_remove_rate(struct drm_dp_link *link, unsigned long rate) 112 { 113 unsigned int i; 114 115 for (i = 0; i < link->num_rates; i++) 116 if (rate == link->rates[i]) 117 break; 118 119 if (i == link->num_rates) 120 return -EINVAL; 121 122 link->num_rates--; 123 124 while (i < link->num_rates) { 125 link->rates[i] = link->rates[i + 1]; 126 i++; 127 } 128 129 return 0; 130 } 131 132 /** 133 * drm_dp_link_update_rates() - normalize the supported link rates array 134 * @link: the link for which to normalize the supported link rates 135 * 136 * Users should call this function after they've manually modified the array 137 * of supported link rates. This function removes any stale entries, compacts 138 * the array and updates the supported link rate count. Note that calling the 139 * drm_dp_link_remove_rate() function already does this janitorial work. 140 * 141 * See also: 142 * drm_dp_link_add_rate(), drm_dp_link_remove_rate() 143 */ 144 void drm_dp_link_update_rates(struct drm_dp_link *link) 145 { 146 unsigned int i, count = 0; 147 148 for (i = 0; i < link->num_rates; i++) { 149 if (link->rates[i] != 0) 150 link->rates[count++] = link->rates[i]; 151 } 152 153 for (i = count; i < link->num_rates; i++) 154 link->rates[i] = 0; 155 156 link->num_rates = count; 157 } 158 159 /** 160 * drm_dp_link_probe() - probe a DisplayPort link for capabilities 161 * @aux: DisplayPort AUX channel 162 * @link: pointer to structure in which to return link capabilities 163 * 164 * The structure filled in by this function can usually be passed directly 165 * into drm_dp_link_power_up() and drm_dp_link_configure() to power up and 166 * configure the link based on the link's capabilities. 167 * 168 * Returns 0 on success or a negative error code on failure. 169 */ 170 int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link) 171 { 172 u8 dpcd[DP_RECEIVER_CAP_SIZE], value; 173 unsigned int rd_interval; 174 int err; 175 176 drm_dp_link_reset(link); 177 178 err = drm_dp_dpcd_read(aux, DP_DPCD_REV, dpcd, sizeof(dpcd)); 179 if (err < 0) 180 return err; 181 182 link->revision = dpcd[DP_DPCD_REV]; 183 link->max_rate = drm_dp_max_link_rate(dpcd); 184 link->max_lanes = drm_dp_max_lane_count(dpcd); 185 186 link->caps.enhanced_framing = drm_dp_enhanced_frame_cap(dpcd); 187 link->caps.tps3_supported = drm_dp_tps3_supported(dpcd); 188 link->caps.fast_training = drm_dp_fast_training_cap(dpcd); 189 link->caps.channel_coding = drm_dp_channel_coding_supported(dpcd); 190 191 if (drm_dp_alternate_scrambler_reset_cap(dpcd)) { 192 link->caps.alternate_scrambler_reset = true; 193 194 err = drm_dp_dpcd_readb(aux, DP_EDP_DPCD_REV, &value); 195 if (err < 0) 196 return err; 197 198 if (value >= ARRAY_SIZE(drm_dp_edp_revisions)) 199 DRM_ERROR("unsupported eDP version: %02x\n", value); 200 else 201 link->edp = drm_dp_edp_revisions[value]; 202 } 203 204 /* 205 * The DPCD stores the AUX read interval in units of 4 ms. There are 206 * two special cases: 207 * 208 * 1) if the TRAINING_AUX_RD_INTERVAL field is 0, the clock recovery 209 * and channel equalization should use 100 us or 400 us AUX read 210 * intervals, respectively 211 * 212 * 2) for DP v1.4 and above, clock recovery should always use 100 us 213 * AUX read intervals 214 */ 215 rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] & 216 DP_TRAINING_AUX_RD_MASK; 217 218 if (rd_interval > 4) { 219 DRM_DEBUG_KMS("AUX interval %u out of range (max. 4)\n", 220 rd_interval); 221 rd_interval = 4; 222 } 223 224 rd_interval *= 4 * USEC_PER_MSEC; 225 226 if (rd_interval == 0 || link->revision >= DP_DPCD_REV_14) 227 link->aux_rd_interval.cr = 100; 228 229 if (rd_interval == 0) 230 link->aux_rd_interval.ce = 400; 231 232 link->rate = link->max_rate; 233 link->lanes = link->max_lanes; 234 235 /* Parse SUPPORTED_LINK_RATES from eDP 1.4 */ 236 if (link->edp >= 0x14) { 237 u8 supported_rates[DP_MAX_SUPPORTED_RATES * 2]; 238 unsigned int i; 239 u16 rate; 240 241 err = drm_dp_dpcd_read(aux, DP_SUPPORTED_LINK_RATES, 242 supported_rates, 243 sizeof(supported_rates)); 244 if (err < 0) 245 return err; 246 247 for (i = 0; i < DP_MAX_SUPPORTED_RATES; i++) { 248 rate = supported_rates[i * 2 + 1] << 8 | 249 supported_rates[i * 2 + 0]; 250 251 drm_dp_link_add_rate(link, rate * 200); 252 } 253 } 254 255 return 0; 256 } 257 258 /** 259 * drm_dp_link_power_up() - power up a DisplayPort link 260 * @aux: DisplayPort AUX channel 261 * @link: pointer to a structure containing the link configuration 262 * 263 * Returns 0 on success or a negative error code on failure. 264 */ 265 int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link) 266 { 267 u8 value; 268 int err; 269 270 /* DP_SET_POWER register is only available on DPCD v1.1 and later */ 271 if (link->revision < 0x11) 272 return 0; 273 274 err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value); 275 if (err < 0) 276 return err; 277 278 value &= ~DP_SET_POWER_MASK; 279 value |= DP_SET_POWER_D0; 280 281 err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value); 282 if (err < 0) 283 return err; 284 285 /* 286 * According to the DP 1.1 specification, a "Sink Device must exit the 287 * power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink 288 * Control Field" (register 0x600). 289 */ 290 usleep_range(1000, 2000); 291 292 return 0; 293 } 294 295 /** 296 * drm_dp_link_power_down() - power down a DisplayPort link 297 * @aux: DisplayPort AUX channel 298 * @link: pointer to a structure containing the link configuration 299 * 300 * Returns 0 on success or a negative error code on failure. 301 */ 302 int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link) 303 { 304 u8 value; 305 int err; 306 307 /* DP_SET_POWER register is only available on DPCD v1.1 and later */ 308 if (link->revision < 0x11) 309 return 0; 310 311 err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value); 312 if (err < 0) 313 return err; 314 315 value &= ~DP_SET_POWER_MASK; 316 value |= DP_SET_POWER_D3; 317 318 err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value); 319 if (err < 0) 320 return err; 321 322 return 0; 323 } 324 325 /** 326 * drm_dp_link_configure() - configure a DisplayPort link 327 * @aux: DisplayPort AUX channel 328 * @link: pointer to a structure containing the link configuration 329 * 330 * Returns 0 on success or a negative error code on failure. 331 */ 332 int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link) 333 { 334 u8 values[2], value; 335 int err; 336 337 if (link->ops && link->ops->configure) { 338 err = link->ops->configure(link); 339 if (err < 0) { 340 DRM_ERROR("failed to configure DP link: %d\n", err); 341 return err; 342 } 343 } 344 345 values[0] = drm_dp_link_rate_to_bw_code(link->rate); 346 values[1] = link->lanes; 347 348 if (link->caps.enhanced_framing) 349 values[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN; 350 351 err = drm_dp_dpcd_write(aux, DP_LINK_BW_SET, values, sizeof(values)); 352 if (err < 0) 353 return err; 354 355 if (link->caps.channel_coding) 356 value = DP_SET_ANSI_8B10B; 357 else 358 value = 0; 359 360 err = drm_dp_dpcd_writeb(aux, DP_MAIN_LINK_CHANNEL_CODING_SET, value); 361 if (err < 0) 362 return err; 363 364 if (link->caps.alternate_scrambler_reset) { 365 err = drm_dp_dpcd_writeb(aux, DP_EDP_CONFIGURATION_SET, 366 DP_ALTERNATE_SCRAMBLER_RESET_ENABLE); 367 if (err < 0) 368 return err; 369 } 370 371 return 0; 372 } 373 374 /** 375 * drm_dp_link_choose() - choose the lowest possible configuration for a mode 376 * @link: DRM DP link object 377 * @mode: DRM display mode 378 * @info: DRM display information 379 * 380 * According to the eDP specification, a source should select a configuration 381 * with the lowest number of lanes and the lowest possible link rate that can 382 * match the bitrate requirements of a video mode. However it must ensure not 383 * to exceed the capabilities of the sink. 384 * 385 * Returns: 0 on success or a negative error code on failure. 386 */ 387 int drm_dp_link_choose(struct drm_dp_link *link, 388 const struct drm_display_mode *mode, 389 const struct drm_display_info *info) 390 { 391 /* available link symbol clock rates */ 392 static const unsigned int rates[3] = { 162000, 270000, 540000 }; 393 /* available number of lanes */ 394 static const unsigned int lanes[3] = { 1, 2, 4 }; 395 unsigned long requirement, capacity; 396 unsigned int rate = link->max_rate; 397 unsigned int i, j; 398 399 /* bandwidth requirement */ 400 requirement = mode->clock * info->bpc * 3; 401 402 for (i = 0; i < ARRAY_SIZE(lanes) && lanes[i] <= link->max_lanes; i++) { 403 for (j = 0; j < ARRAY_SIZE(rates) && rates[j] <= rate; j++) { 404 /* 405 * Capacity for this combination of lanes and rate, 406 * factoring in the ANSI 8B/10B encoding. 407 * 408 * Link rates in the DRM DP helpers are really link 409 * symbol frequencies, so a tenth of the actual rate 410 * of the link. 411 */ 412 capacity = lanes[i] * (rates[j] * 10) * 8 / 10; 413 414 if (capacity >= requirement) { 415 DRM_DEBUG_KMS("using %u lanes at %u kHz (%lu/%lu kbps)\n", 416 lanes[i], rates[j], requirement, 417 capacity); 418 link->lanes = lanes[i]; 419 link->rate = rates[j]; 420 return 0; 421 } 422 } 423 } 424 425 return -ERANGE; 426 } 427 428 /** 429 * DOC: Link training 430 * 431 * These functions contain common logic and helpers to implement DisplayPort 432 * link training. 433 */ 434 435 /** 436 * drm_dp_link_train_init() - initialize DisplayPort link training state 437 * @train: DisplayPort link training state 438 */ 439 void drm_dp_link_train_init(struct drm_dp_link_train *train) 440 { 441 struct drm_dp_link_train_set *request = &train->request; 442 struct drm_dp_link_train_set *adjust = &train->adjust; 443 unsigned int i; 444 445 for (i = 0; i < 4; i++) { 446 request->voltage_swing[i] = 0; 447 adjust->voltage_swing[i] = 0; 448 449 request->pre_emphasis[i] = 0; 450 adjust->pre_emphasis[i] = 0; 451 452 request->post_cursor[i] = 0; 453 adjust->post_cursor[i] = 0; 454 } 455 456 train->pattern = DP_TRAINING_PATTERN_DISABLE; 457 train->clock_recovered = false; 458 train->channel_equalized = false; 459 } 460 461 static bool drm_dp_link_train_valid(const struct drm_dp_link_train *train) 462 { 463 return train->clock_recovered && train->channel_equalized; 464 } 465 466 static int drm_dp_link_apply_training(struct drm_dp_link *link) 467 { 468 struct drm_dp_link_train_set *request = &link->train.request; 469 unsigned int lanes = link->lanes, *vs, *pe, *pc, i; 470 struct drm_dp_aux *aux = link->aux; 471 u8 values[4], pattern = 0; 472 int err; 473 474 err = link->ops->apply_training(link); 475 if (err < 0) { 476 DRM_ERROR("failed to apply link training: %d\n", err); 477 return err; 478 } 479 480 vs = request->voltage_swing; 481 pe = request->pre_emphasis; 482 pc = request->post_cursor; 483 484 /* write currently selected voltage-swing and pre-emphasis levels */ 485 for (i = 0; i < lanes; i++) 486 values[i] = DP_TRAIN_VOLTAGE_SWING_LEVEL(vs[i]) | 487 DP_TRAIN_PRE_EMPHASIS_LEVEL(pe[i]); 488 489 err = drm_dp_dpcd_write(aux, DP_TRAINING_LANE0_SET, values, lanes); 490 if (err < 0) { 491 DRM_ERROR("failed to set training parameters: %d\n", err); 492 return err; 493 } 494 495 /* write currently selected post-cursor level (if supported) */ 496 if (link->revision >= 0x12 && link->rate == 540000) { 497 values[0] = values[1] = 0; 498 499 for (i = 0; i < lanes; i++) 500 values[i / 2] |= DP_LANE_POST_CURSOR(i, pc[i]); 501 502 err = drm_dp_dpcd_write(aux, DP_TRAINING_LANE0_1_SET2, values, 503 DIV_ROUND_UP(lanes, 2)); 504 if (err < 0) { 505 DRM_ERROR("failed to set post-cursor: %d\n", err); 506 return err; 507 } 508 } 509 510 /* write link pattern */ 511 if (link->train.pattern != DP_TRAINING_PATTERN_DISABLE) 512 pattern |= DP_LINK_SCRAMBLING_DISABLE; 513 514 pattern |= link->train.pattern; 515 516 err = drm_dp_dpcd_writeb(aux, DP_TRAINING_PATTERN_SET, pattern); 517 if (err < 0) { 518 DRM_ERROR("failed to set training pattern: %d\n", err); 519 return err; 520 } 521 522 return 0; 523 } 524 525 static void drm_dp_link_train_wait(struct drm_dp_link *link) 526 { 527 unsigned long min = 0; 528 529 switch (link->train.pattern) { 530 case DP_TRAINING_PATTERN_1: 531 min = link->aux_rd_interval.cr; 532 break; 533 534 case DP_TRAINING_PATTERN_2: 535 case DP_TRAINING_PATTERN_3: 536 min = link->aux_rd_interval.ce; 537 break; 538 539 default: 540 break; 541 } 542 543 if (min > 0) 544 usleep_range(min, 2 * min); 545 } 546 547 static void drm_dp_link_get_adjustments(struct drm_dp_link *link, 548 u8 status[DP_LINK_STATUS_SIZE]) 549 { 550 struct drm_dp_link_train_set *adjust = &link->train.adjust; 551 unsigned int i; 552 553 for (i = 0; i < link->lanes; i++) { 554 adjust->voltage_swing[i] = 555 drm_dp_get_adjust_request_voltage(status, i) >> 556 DP_TRAIN_VOLTAGE_SWING_SHIFT; 557 558 adjust->pre_emphasis[i] = 559 drm_dp_get_adjust_request_pre_emphasis(status, i) >> 560 DP_TRAIN_PRE_EMPHASIS_SHIFT; 561 562 adjust->post_cursor[i] = 563 drm_dp_get_adjust_request_post_cursor(status, i); 564 } 565 } 566 567 static void drm_dp_link_train_adjust(struct drm_dp_link_train *train) 568 { 569 struct drm_dp_link_train_set *request = &train->request; 570 struct drm_dp_link_train_set *adjust = &train->adjust; 571 unsigned int i; 572 573 for (i = 0; i < 4; i++) 574 if (request->voltage_swing[i] != adjust->voltage_swing[i]) 575 request->voltage_swing[i] = adjust->voltage_swing[i]; 576 577 for (i = 0; i < 4; i++) 578 if (request->pre_emphasis[i] != adjust->pre_emphasis[i]) 579 request->pre_emphasis[i] = adjust->pre_emphasis[i]; 580 581 for (i = 0; i < 4; i++) 582 if (request->post_cursor[i] != adjust->post_cursor[i]) 583 request->post_cursor[i] = adjust->post_cursor[i]; 584 } 585 586 static int drm_dp_link_recover_clock(struct drm_dp_link *link) 587 { 588 u8 status[DP_LINK_STATUS_SIZE]; 589 int err; 590 591 err = drm_dp_link_apply_training(link); 592 if (err < 0) 593 return err; 594 595 drm_dp_link_train_wait(link); 596 597 err = drm_dp_dpcd_read_link_status(link->aux, status); 598 if (err < 0) { 599 DRM_ERROR("failed to read link status: %d\n", err); 600 return err; 601 } 602 603 if (!drm_dp_clock_recovery_ok(status, link->lanes)) 604 drm_dp_link_get_adjustments(link, status); 605 else 606 link->train.clock_recovered = true; 607 608 return 0; 609 } 610 611 static int drm_dp_link_clock_recovery(struct drm_dp_link *link) 612 { 613 unsigned int repeat; 614 int err; 615 616 /* start clock recovery using training pattern 1 */ 617 link->train.pattern = DP_TRAINING_PATTERN_1; 618 619 for (repeat = 1; repeat < 5; repeat++) { 620 err = drm_dp_link_recover_clock(link); 621 if (err < 0) { 622 DRM_ERROR("failed to recover clock: %d\n", err); 623 return err; 624 } 625 626 if (link->train.clock_recovered) 627 break; 628 629 drm_dp_link_train_adjust(&link->train); 630 } 631 632 return 0; 633 } 634 635 static int drm_dp_link_equalize_channel(struct drm_dp_link *link) 636 { 637 struct drm_dp_aux *aux = link->aux; 638 u8 status[DP_LINK_STATUS_SIZE]; 639 int err; 640 641 err = drm_dp_link_apply_training(link); 642 if (err < 0) 643 return err; 644 645 drm_dp_link_train_wait(link); 646 647 err = drm_dp_dpcd_read_link_status(aux, status); 648 if (err < 0) { 649 DRM_ERROR("failed to read link status: %d\n", err); 650 return err; 651 } 652 653 if (!drm_dp_clock_recovery_ok(status, link->lanes)) { 654 DRM_ERROR("clock recovery lost while equalizing channel\n"); 655 link->train.clock_recovered = false; 656 return 0; 657 } 658 659 if (!drm_dp_channel_eq_ok(status, link->lanes)) 660 drm_dp_link_get_adjustments(link, status); 661 else 662 link->train.channel_equalized = true; 663 664 return 0; 665 } 666 667 static int drm_dp_link_channel_equalization(struct drm_dp_link *link) 668 { 669 unsigned int repeat; 670 int err; 671 672 /* start channel equalization using pattern 2 or 3 */ 673 if (link->caps.tps3_supported) 674 link->train.pattern = DP_TRAINING_PATTERN_3; 675 else 676 link->train.pattern = DP_TRAINING_PATTERN_2; 677 678 for (repeat = 1; repeat < 5; repeat++) { 679 err = drm_dp_link_equalize_channel(link); 680 if (err < 0) { 681 DRM_ERROR("failed to equalize channel: %d\n", err); 682 return err; 683 } 684 685 if (link->train.channel_equalized) 686 break; 687 688 drm_dp_link_train_adjust(&link->train); 689 } 690 691 return 0; 692 } 693 694 static int drm_dp_link_downgrade(struct drm_dp_link *link) 695 { 696 switch (link->rate) { 697 case 162000: 698 return -EINVAL; 699 700 case 270000: 701 link->rate = 162000; 702 break; 703 704 case 540000: 705 link->rate = 270000; 706 return 0; 707 } 708 709 return 0; 710 } 711 712 static void drm_dp_link_train_disable(struct drm_dp_link *link) 713 { 714 int err; 715 716 link->train.pattern = DP_TRAINING_PATTERN_DISABLE; 717 718 err = drm_dp_link_apply_training(link); 719 if (err < 0) 720 DRM_ERROR("failed to disable link training: %d\n", err); 721 } 722 723 static int drm_dp_link_train_full(struct drm_dp_link *link) 724 { 725 int err; 726 727 retry: 728 DRM_DEBUG_KMS("full-training link: %u lane%s at %u MHz\n", 729 link->lanes, (link->lanes > 1) ? "s" : "", 730 link->rate / 100); 731 732 err = drm_dp_link_configure(link->aux, link); 733 if (err < 0) { 734 DRM_ERROR("failed to configure DP link: %d\n", err); 735 return err; 736 } 737 738 err = drm_dp_link_clock_recovery(link); 739 if (err < 0) { 740 DRM_ERROR("clock recovery failed: %d\n", err); 741 goto out; 742 } 743 744 if (!link->train.clock_recovered) { 745 DRM_ERROR("clock recovery failed, downgrading link\n"); 746 747 err = drm_dp_link_downgrade(link); 748 if (err < 0) 749 goto out; 750 751 goto retry; 752 } 753 754 DRM_DEBUG_KMS("clock recovery succeeded\n"); 755 756 err = drm_dp_link_channel_equalization(link); 757 if (err < 0) { 758 DRM_ERROR("channel equalization failed: %d\n", err); 759 goto out; 760 } 761 762 if (!link->train.channel_equalized) { 763 DRM_ERROR("channel equalization failed, downgrading link\n"); 764 765 err = drm_dp_link_downgrade(link); 766 if (err < 0) 767 goto out; 768 769 goto retry; 770 } 771 772 DRM_DEBUG_KMS("channel equalization succeeded\n"); 773 774 out: 775 drm_dp_link_train_disable(link); 776 return err; 777 } 778 779 static int drm_dp_link_train_fast(struct drm_dp_link *link) 780 { 781 u8 status[DP_LINK_STATUS_SIZE]; 782 int err; 783 784 DRM_DEBUG_KMS("fast-training link: %u lane%s at %u MHz\n", 785 link->lanes, (link->lanes > 1) ? "s" : "", 786 link->rate / 100); 787 788 err = drm_dp_link_configure(link->aux, link); 789 if (err < 0) { 790 DRM_ERROR("failed to configure DP link: %d\n", err); 791 return err; 792 } 793 794 /* transmit training pattern 1 for 500 microseconds */ 795 link->train.pattern = DP_TRAINING_PATTERN_1; 796 797 err = drm_dp_link_apply_training(link); 798 if (err < 0) 799 goto out; 800 801 usleep_range(500, 1000); 802 803 /* transmit training pattern 2 or 3 for 500 microseconds */ 804 if (link->caps.tps3_supported) 805 link->train.pattern = DP_TRAINING_PATTERN_3; 806 else 807 link->train.pattern = DP_TRAINING_PATTERN_2; 808 809 err = drm_dp_link_apply_training(link); 810 if (err < 0) 811 goto out; 812 813 usleep_range(500, 1000); 814 815 err = drm_dp_dpcd_read_link_status(link->aux, status); 816 if (err < 0) { 817 DRM_ERROR("failed to read link status: %d\n", err); 818 goto out; 819 } 820 821 if (!drm_dp_clock_recovery_ok(status, link->lanes)) { 822 DRM_ERROR("clock recovery failed\n"); 823 err = -EIO; 824 } 825 826 if (!drm_dp_channel_eq_ok(status, link->lanes)) { 827 DRM_ERROR("channel equalization failed\n"); 828 err = -EIO; 829 } 830 831 out: 832 drm_dp_link_train_disable(link); 833 return err; 834 } 835 836 /** 837 * drm_dp_link_train() - perform DisplayPort link training 838 * @link: a DP link object 839 * 840 * Uses the context stored in the DP link object to perform link training. It 841 * is expected that drivers will call drm_dp_link_probe() to obtain the link 842 * capabilities before performing link training. 843 * 844 * If the sink supports fast link training (no AUX CH handshake) and valid 845 * training settings are available, this function will try to perform fast 846 * link training and fall back to full link training on failure. 847 * 848 * Returns: 0 on success or a negative error code on failure. 849 */ 850 int drm_dp_link_train(struct drm_dp_link *link) 851 { 852 int err; 853 854 drm_dp_link_train_init(&link->train); 855 856 if (link->caps.fast_training) { 857 if (drm_dp_link_train_valid(&link->train)) { 858 err = drm_dp_link_train_fast(link); 859 if (err < 0) 860 DRM_ERROR("fast link training failed: %d\n", 861 err); 862 else 863 return 0; 864 } else { 865 DRM_DEBUG_KMS("training parameters not available\n"); 866 } 867 } else { 868 DRM_DEBUG_KMS("fast link training not supported\n"); 869 } 870 871 err = drm_dp_link_train_full(link); 872 if (err < 0) 873 DRM_ERROR("full link training failed: %d\n", err); 874 875 return err; 876 } 877