root/drivers/gpu/drm/i915/display/intel_dp_link_training.c

DEFINITIONS

1. intel_dp_dump_link_status
2. intel_get_adjust_train
3. intel_dp_set_link_train
4. intel_dp_reset_link_train
5. intel_dp_update_link_train
6. intel_dp_link_max_vswing_reached
7. intel_dp_link_training_clock_recovery
8. intel_dp_training_pattern
9. intel_dp_link_training_channel_equalization
10. intel_dp_stop_link_train
11. intel_dp_start_link_train

   1 /*
   2  * Copyright © 2008-2015 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23 
  24 #include "intel_display_types.h"
  25 #include "intel_dp.h"
  26 #include "intel_dp_link_training.h"
  27 
  28 static void
  29 intel_dp_dump_link_status(const u8 link_status[DP_LINK_STATUS_SIZE])
  30 {
  31 
  32         DRM_DEBUG_KMS("ln0_1:0x%x ln2_3:0x%x align:0x%x sink:0x%x adj_req0_1:0x%x adj_req2_3:0x%x",
  33                       link_status[0], link_status[1], link_status[2],
  34                       link_status[3], link_status[4], link_status[5]);
  35 }
  36 
  37 static void
  38 intel_get_adjust_train(struct intel_dp *intel_dp,
  39                        const u8 link_status[DP_LINK_STATUS_SIZE])
  40 {
  41         u8 v = 0;
  42         u8 p = 0;
  43         int lane;
  44         u8 voltage_max;
  45         u8 preemph_max;
  46 
  47         for (lane = 0; lane < intel_dp->lane_count; lane++) {
  48                 u8 this_v = drm_dp_get_adjust_request_voltage(link_status, lane);
  49                 u8 this_p = drm_dp_get_adjust_request_pre_emphasis(link_status, lane);
  50 
  51                 if (this_v > v)
  52                         v = this_v;
  53                 if (this_p > p)
  54                         p = this_p;
  55         }
  56 
  57         voltage_max = intel_dp_voltage_max(intel_dp);
  58         if (v >= voltage_max)
  59                 v = voltage_max | DP_TRAIN_MAX_SWING_REACHED;
  60 
  61         preemph_max = intel_dp_pre_emphasis_max(intel_dp, v);
  62         if (p >= preemph_max)
  63                 p = preemph_max | DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
  64 
  65         for (lane = 0; lane < 4; lane++)
  66                 intel_dp->train_set[lane] = v | p;
  67 }
  68 
  69 static bool
  70 intel_dp_set_link_train(struct intel_dp *intel_dp,
  71                         u8 dp_train_pat)
  72 {
  73         u8 buf[sizeof(intel_dp->train_set) + 1];
  74         int ret, len;
  75 
  76         intel_dp_program_link_training_pattern(intel_dp, dp_train_pat);
  77 
  78         buf[0] = dp_train_pat;
  79         if ((dp_train_pat & DP_TRAINING_PATTERN_MASK) ==
  80             DP_TRAINING_PATTERN_DISABLE) {
  81                 /* don't write DP_TRAINING_LANEx_SET on disable */
  82                 len = 1;
  83         } else {
  84                 /* DP_TRAINING_LANEx_SET follow DP_TRAINING_PATTERN_SET */
  85                 memcpy(buf + 1, intel_dp->train_set, intel_dp->lane_count);
  86                 len = intel_dp->lane_count + 1;
  87         }
  88 
  89         ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET,
  90                                 buf, len);
  91 
  92         return ret == len;
  93 }
  94 
  95 static bool
  96 intel_dp_reset_link_train(struct intel_dp *intel_dp,
  97                         u8 dp_train_pat)
  98 {
  99         memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
 100         intel_dp_set_signal_levels(intel_dp);
 101         return intel_dp_set_link_train(intel_dp, dp_train_pat);
 102 }
 103 
 104 static bool
 105 intel_dp_update_link_train(struct intel_dp *intel_dp)
 106 {
 107         int ret;
 108 
 109         intel_dp_set_signal_levels(intel_dp);
 110 
 111         ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_LANE0_SET,
 112                                 intel_dp->train_set, intel_dp->lane_count);
 113 
 114         return ret == intel_dp->lane_count;
 115 }
 116 
 117 static bool intel_dp_link_max_vswing_reached(struct intel_dp *intel_dp)
 118 {
 119         int lane;
 120 
 121         for (lane = 0; lane < intel_dp->lane_count; lane++)
 122                 if ((intel_dp->train_set[lane] &
 123                      DP_TRAIN_MAX_SWING_REACHED) == 0)
 124                         return false;
 125 
 126         return true;
 127 }
 128 
 129 /* Enable corresponding port and start training pattern 1 */
 130 static bool
 131 intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
 132 {
 133         u8 voltage;
 134         int voltage_tries, cr_tries, max_cr_tries;
 135         bool max_vswing_reached = false;
 136         u8 link_config[2];
 137         u8 link_bw, rate_select;
 138 
 139         if (intel_dp->prepare_link_retrain)
 140                 intel_dp->prepare_link_retrain(intel_dp);
 141 
 142         intel_dp_compute_rate(intel_dp, intel_dp->link_rate,
 143                               &link_bw, &rate_select);
 144 
 145         if (link_bw)
 146                 DRM_DEBUG_KMS("Using LINK_BW_SET value %02x\n", link_bw);
 147         else
 148                 DRM_DEBUG_KMS("Using LINK_RATE_SET value %02x\n", rate_select);
 149 
 150         /* Write the link configuration data */
 151         link_config[0] = link_bw;
 152         link_config[1] = intel_dp->lane_count;
 153         if (drm_dp_enhanced_frame_cap(intel_dp->dpcd))
 154                 link_config[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
 155         drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, 2);
 156 
 157         /* eDP 1.4 rate select method. */
 158         if (!link_bw)
 159                 drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_RATE_SET,
 160                                   &rate_select, 1);
 161 
 162         link_config[0] = 0;
 163         link_config[1] = DP_SET_ANSI_8B10B;
 164         drm_dp_dpcd_write(&intel_dp->aux, DP_DOWNSPREAD_CTRL, link_config, 2);
 165 
 166         intel_dp->DP |= DP_PORT_EN;
 167 
 168         /* clock recovery */
 169         if (!intel_dp_reset_link_train(intel_dp,
 170                                        DP_TRAINING_PATTERN_1 |
 171                                        DP_LINK_SCRAMBLING_DISABLE)) {
 172                 DRM_ERROR("failed to enable link training\n");
 173                 return false;
 174         }
 175 
 176         /*
 177          * The DP 1.4 spec defines the max clock recovery retries value
 178          * as 10 but for pre-DP 1.4 devices we set a very tolerant
 179          * retry limit of 80 (4 voltage levels x 4 preemphasis levels x
 180          * x 5 identical voltage retries). Since the previous specs didn't
 181          * define a limit and created the possibility of an infinite loop
 182          * we want to prevent any sync from triggering that corner case.
 183          */
 184         if (intel_dp->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14)
 185                 max_cr_tries = 10;
 186         else
 187                 max_cr_tries = 80;
 188 
 189         voltage_tries = 1;
 190         for (cr_tries = 0; cr_tries < max_cr_tries; ++cr_tries) {
 191                 u8 link_status[DP_LINK_STATUS_SIZE];
 192 
 193                 drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
 194 
 195                 if (!intel_dp_get_link_status(intel_dp, link_status)) {
 196                         DRM_ERROR("failed to get link status\n");
 197                         return false;
 198                 }
 199 
 200                 if (drm_dp_clock_recovery_ok(link_status, intel_dp->lane_count)) {
 201                         DRM_DEBUG_KMS("clock recovery OK\n");
 202                         return true;
 203                 }
 204 
 205                 if (voltage_tries == 5) {
 206                         DRM_DEBUG_KMS("Same voltage tried 5 times\n");
 207                         return false;
 208                 }
 209 
 210                 if (max_vswing_reached) {
 211                         DRM_DEBUG_KMS("Max Voltage Swing reached\n");
 212                         return false;
 213                 }
 214 
 215                 voltage = intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK;
 216 
 217                 /* Update training set as requested by target */
 218                 intel_get_adjust_train(intel_dp, link_status);
 219                 if (!intel_dp_update_link_train(intel_dp)) {
 220                         DRM_ERROR("failed to update link training\n");
 221                         return false;
 222                 }
 223 
 224                 if ((intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK) ==
 225                     voltage)
 226                         ++voltage_tries;
 227                 else
 228                         voltage_tries = 1;
 229 
 230                 if (intel_dp_link_max_vswing_reached(intel_dp))
 231                         max_vswing_reached = true;
 232 
 233         }
 234         DRM_ERROR("Failed clock recovery %d times, giving up!\n", max_cr_tries);
 235         return false;
 236 }
 237 
 238 /*
 239  * Pick training pattern for channel equalization. Training pattern 4 for HBR3
 240  * or for 1.4 devices that support it, training Pattern 3 for HBR2
 241  * or 1.2 devices that support it, Training Pattern 2 otherwise.
 242  */
 243 static u32 intel_dp_training_pattern(struct intel_dp *intel_dp)
 244 {
 245         bool source_tps3, sink_tps3, source_tps4, sink_tps4;
 246 
 247         /*
 248          * Intel platforms that support HBR3 also support TPS4. It is mandatory
 249          * for all downstream devices that support HBR3. There are no known eDP
 250          * panels that support TPS4 as of Feb 2018 as per VESA eDP_v1.4b_E1
 251          * specification.
 252          */
 253         source_tps4 = intel_dp_source_supports_hbr3(intel_dp);
 254         sink_tps4 = drm_dp_tps4_supported(intel_dp->dpcd);
 255         if (source_tps4 && sink_tps4) {
 256                 return DP_TRAINING_PATTERN_4;
 257         } else if (intel_dp->link_rate == 810000) {
 258                 if (!source_tps4)
 259                         DRM_DEBUG_KMS("8.1 Gbps link rate without source HBR3/TPS4 support\n");
 260                 if (!sink_tps4)
 261                         DRM_DEBUG_KMS("8.1 Gbps link rate without sink TPS4 support\n");
 262         }
 263         /*
 264          * Intel platforms that support HBR2 also support TPS3. TPS3 support is
 265          * also mandatory for downstream devices that support HBR2. However, not
 266          * all sinks follow the spec.
 267          */
 268         source_tps3 = intel_dp_source_supports_hbr2(intel_dp);
 269         sink_tps3 = drm_dp_tps3_supported(intel_dp->dpcd);
 270         if (source_tps3 && sink_tps3) {
 271                 return  DP_TRAINING_PATTERN_3;
 272         } else if (intel_dp->link_rate >= 540000) {
 273                 if (!source_tps3)
 274                         DRM_DEBUG_KMS(">=5.4/6.48 Gbps link rate without source HBR2/TPS3 support\n");
 275                 if (!sink_tps3)
 276                         DRM_DEBUG_KMS(">=5.4/6.48 Gbps link rate without sink TPS3 support\n");
 277         }
 278 
 279         return DP_TRAINING_PATTERN_2;
 280 }
 281 
 282 static bool
 283 intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
 284 {
 285         int tries;
 286         u32 training_pattern;
 287         u8 link_status[DP_LINK_STATUS_SIZE];
 288         bool channel_eq = false;
 289 
 290         training_pattern = intel_dp_training_pattern(intel_dp);
 291         /* Scrambling is disabled for TPS2/3 and enabled for TPS4 */
 292         if (training_pattern != DP_TRAINING_PATTERN_4)
 293                 training_pattern |= DP_LINK_SCRAMBLING_DISABLE;
 294 
 295         /* channel equalization */
 296         if (!intel_dp_set_link_train(intel_dp,
 297                                      training_pattern)) {
 298                 DRM_ERROR("failed to start channel equalization\n");
 299                 return false;
 300         }
 301 
 302         for (tries = 0; tries < 5; tries++) {
 303 
 304                 drm_dp_link_train_channel_eq_delay(intel_dp->dpcd);
 305                 if (!intel_dp_get_link_status(intel_dp, link_status)) {
 306                         DRM_ERROR("failed to get link status\n");
 307                         break;
 308                 }
 309 
 310                 /* Make sure clock is still ok */
 311                 if (!drm_dp_clock_recovery_ok(link_status,
 312                                               intel_dp->lane_count)) {
 313                         intel_dp_dump_link_status(link_status);
 314                         DRM_DEBUG_KMS("Clock recovery check failed, cannot "
 315                                       "continue channel equalization\n");
 316                         break;
 317                 }
 318 
 319                 if (drm_dp_channel_eq_ok(link_status,
 320                                          intel_dp->lane_count)) {
 321                         channel_eq = true;
 322                         DRM_DEBUG_KMS("Channel EQ done. DP Training "
 323                                       "successful\n");
 324                         break;
 325                 }
 326 
 327                 /* Update training set as requested by target */
 328                 intel_get_adjust_train(intel_dp, link_status);
 329                 if (!intel_dp_update_link_train(intel_dp)) {
 330                         DRM_ERROR("failed to update link training\n");
 331                         break;
 332                 }
 333         }
 334 
 335         /* Try 5 times, else fail and try at lower BW */
 336         if (tries == 5) {
 337                 intel_dp_dump_link_status(link_status);
 338                 DRM_DEBUG_KMS("Channel equalization failed 5 times\n");
 339         }
 340 
 341         intel_dp_set_idle_link_train(intel_dp);
 342 
 343         return channel_eq;
 344 
 345 }
 346 
 347 void intel_dp_stop_link_train(struct intel_dp *intel_dp)
 348 {
 349         intel_dp->link_trained = true;
 350 
 351         intel_dp_set_link_train(intel_dp,
 352                                 DP_TRAINING_PATTERN_DISABLE);
 353 }
 354 
 355 void
 356 intel_dp_start_link_train(struct intel_dp *intel_dp)
 357 {
 358         struct intel_connector *intel_connector = intel_dp->attached_connector;
 359 
 360         if (!intel_dp_link_training_clock_recovery(intel_dp))
 361                 goto failure_handling;
 362         if (!intel_dp_link_training_channel_equalization(intel_dp))
 363                 goto failure_handling;
 364 
 365         DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training Passed at Link Rate = %d, Lane count = %d",
 366                       intel_connector->base.base.id,
 367                       intel_connector->base.name,
 368                       intel_dp->link_rate, intel_dp->lane_count);
 369         return;
 370 
 371  failure_handling:
 372         DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
 373                       intel_connector->base.base.id,
 374                       intel_connector->base.name,
 375                       intel_dp->link_rate, intel_dp->lane_count);
 376         if (!intel_dp_get_link_train_fallback_values(intel_dp,
 377                                                      intel_dp->link_rate,
 378                                                      intel_dp->lane_count))
 379                 /* Schedule a Hotplug Uevent to userspace to start modeset */
 380                 schedule_work(&intel_connector->modeset_retry_work);
 381         return;
 382 }