drivers/gpu/drm/i915/intel_dp_link_training.c

   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_drv.h"
  25
  26 static void
  27 intel_get_adjust_train(struct intel_dp *intel_dp,
  28                        const uint8_t link_status[DP_LINK_STATUS_SIZE])
  29 {
  30         uint8_t v = 0;
  31         uint8_t p = 0;
  32         int lane;
  33         uint8_t voltage_max;
  34         uint8_t preemph_max;
  35
  36         for (lane = 0; lane < intel_dp->lane_count; lane++) {
  37                 uint8_t this_v = drm_dp_get_adjust_request_voltage(link_status, lane);
  38                 uint8_t this_p = drm_dp_get_adjust_request_pre_emphasis(link_status, lane);
  39
  40                 if (this_v > v)
  41                         v = this_v;
  42                 if (this_p > p)
  43                         p = this_p;
  44         }
  45
  46         voltage_max = intel_dp_voltage_max(intel_dp);
  47         if (v >= voltage_max)
  48                 v = voltage_max | DP_TRAIN_MAX_SWING_REACHED;
  49
  50         preemph_max = intel_dp_pre_emphasis_max(intel_dp, v);
  51         if (p >= preemph_max)
  52                 p = preemph_max | DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
  53
  54         for (lane = 0; lane < 4; lane++)
  55                 intel_dp->train_set[lane] = v | p;
  56 }
  57
  58 static bool
  59 intel_dp_set_link_train(struct intel_dp *intel_dp,
  60                         uint8_t dp_train_pat)
  61 {
  62         uint8_t buf[sizeof(intel_dp->train_set) + 1];
  63         int ret, len;
  64
  65         intel_dp_program_link_training_pattern(intel_dp, dp_train_pat);
  66
  67         buf[0] = dp_train_pat;
  68         if ((dp_train_pat & DP_TRAINING_PATTERN_MASK) ==
  69             DP_TRAINING_PATTERN_DISABLE) {
  70                 /* don't write DP_TRAINING_LANEx_SET on disable */
  71                 len = 1;
  72         } else {
  73                 /* DP_TRAINING_LANEx_SET follow DP_TRAINING_PATTERN_SET */
  74                 memcpy(buf + 1, intel_dp->train_set, intel_dp->lane_count);
  75                 len = intel_dp->lane_count + 1;
  76         }
  77
  78         ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET,
  79                                 buf, len);
  80
  81         return ret == len;
  82 }
  83
  84 static bool
  85 intel_dp_reset_link_train(struct intel_dp *intel_dp,
  86                         uint8_t dp_train_pat)
  87 {
  88         if (!intel_dp->train_set_valid)
  89                 memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
  90         intel_dp_set_signal_levels(intel_dp);
  91         return intel_dp_set_link_train(intel_dp, dp_train_pat);
  92 }
  93
  94 static bool
  95 intel_dp_update_link_train(struct intel_dp *intel_dp)
  96 {
  97         int ret;
  98
  99         intel_dp_set_signal_levels(intel_dp);
 100
 101         ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_LANE0_SET,
 102                                 intel_dp->train_set, intel_dp->lane_count);
 103
 104         return ret == intel_dp->lane_count;
 105 }
 106
 107 /* Enable corresponding port and start training pattern 1 */
 108 static void
 109 intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
 110 {
 111         int i;
 112         uint8_t voltage;
 113         int voltage_tries, loop_tries;
 114         uint8_t link_config[2];
 115         uint8_t link_bw, rate_select;
 116
 117         if (intel_dp->prepare_link_retrain)
 118                 intel_dp->prepare_link_retrain(intel_dp);
 119
 120         intel_dp_compute_rate(intel_dp, intel_dp->link_rate,
 121                               &link_bw, &rate_select);
 122
 123         /* Write the link configuration data */
 124         link_config[0] = link_bw;
 125         link_config[1] = intel_dp->lane_count;
 126         if (drm_dp_enhanced_frame_cap(intel_dp->dpcd))
 127                 link_config[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
 128         drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, 2);
 129         if (intel_dp->num_sink_rates)
 130                 drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_RATE_SET,
 131                                   &rate_select, 1);
 132
 133         link_config[0] = 0;
 134         link_config[1] = DP_SET_ANSI_8B10B;
 135         drm_dp_dpcd_write(&intel_dp->aux, DP_DOWNSPREAD_CTRL, link_config, 2);
 136
 137         intel_dp->DP |= DP_PORT_EN;
 138
 139         /* clock recovery */
 140         if (!intel_dp_reset_link_train(intel_dp,
 141                                        DP_TRAINING_PATTERN_1 |
 142                                        DP_LINK_SCRAMBLING_DISABLE)) {
 143                 DRM_ERROR("failed to enable link training\n");
 144                 return;
 145         }
 146
 147         voltage = 0xff;
 148         voltage_tries = 0;
 149         loop_tries = 0;
 150         for (;;) {
 151                 uint8_t link_status[DP_LINK_STATUS_SIZE];
 152
 153                 drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
 154                 if (!intel_dp_get_link_status(intel_dp, link_status)) {
 155                         DRM_ERROR("failed to get link status\n");
 156                         break;
 157                 }
 158
 159                 if (drm_dp_clock_recovery_ok(link_status, intel_dp->lane_count)) {
 160                         DRM_DEBUG_KMS("clock recovery OK\n");
 161                         break;
 162                 }
 163
 164                 /*
 165                  * if we used previously trained voltage and pre-emphasis values
 166                  * and we don't get clock recovery, reset link training values
 167                  */
 168                 if (intel_dp->train_set_valid) {
 169                         DRM_DEBUG_KMS("clock recovery not ok, reset");
 170                         /* clear the flag as we are not reusing train set */
 171                         intel_dp->train_set_valid = false;
 172                         if (!intel_dp_reset_link_train(intel_dp,
 173                                                        DP_TRAINING_PATTERN_1 |
 174                                                        DP_LINK_SCRAMBLING_DISABLE)) {
 175                                 DRM_ERROR("failed to enable link training\n");
 176                                 return;
 177                         }
 178                         continue;
 179                 }
 180
 181                 /* Check to see if we've tried the max voltage */
 182                 for (i = 0; i < intel_dp->lane_count; i++)
 183                         if ((intel_dp->train_set[i] & DP_TRAIN_MAX_SWING_REACHED) == 0)
 184                                 break;
 185                 if (i == intel_dp->lane_count) {
 186                         ++loop_tries;
 187                         if (loop_tries == 5) {
 188                                 DRM_ERROR("too many full retries, give up\n");
 189                                 break;
 190                         }
 191                         intel_dp_reset_link_train(intel_dp,
 192                                                   DP_TRAINING_PATTERN_1 |
 193                                                   DP_LINK_SCRAMBLING_DISABLE);
 194                         voltage_tries = 0;
 195                         continue;
 196                 }
 197
 198                 /* Check to see if we've tried the same voltage 5 times */
 199                 if ((intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK) == voltage) {
 200                         ++voltage_tries;
 201                         if (voltage_tries == 5) {
 202                                 DRM_ERROR("too many voltage retries, give up\n");
 203                                 break;
 204                         }
 205                 } else
 206                         voltage_tries = 0;
 207                 voltage = intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK;
 208
 209                 /* Update training set as requested by target */
 210                 intel_get_adjust_train(intel_dp, link_status);
 211                 if (!intel_dp_update_link_train(intel_dp)) {
 212                         DRM_ERROR("failed to update link training\n");
 213                         break;
 214                 }
 215         }
 216 }
 217
 218 /*
 219  * Pick training pattern for channel equalization. Training Pattern 3 for HBR2
 220  * or 1.2 devices that support it, Training Pattern 2 otherwise.
 221  */
 222 static u32 intel_dp_training_pattern(struct intel_dp *intel_dp)
 223 {
 224         u32 training_pattern = DP_TRAINING_PATTERN_2;
 225         bool source_tps3, sink_tps3;
 226
 227         /*
 228          * Intel platforms that support HBR2 also support TPS3. TPS3 support is
 229          * also mandatory for downstream devices that support HBR2. However, not
 230          * all sinks follow the spec.
 231          *
 232          * Due to WaDisableHBR2 SKL < B0 is the only exception where TPS3 is
 233          * supported in source but still not enabled.
 234          */
 235         source_tps3 = intel_dp_source_supports_hbr2(intel_dp);
 236         sink_tps3 = drm_dp_tps3_supported(intel_dp->dpcd);
 237
 238         if (source_tps3 && sink_tps3) {
 239                 training_pattern = DP_TRAINING_PATTERN_3;
 240         } else if (intel_dp->link_rate == 540000) {
 241                 if (!source_tps3)
 242                         DRM_DEBUG_KMS("5.4 Gbps link rate without source HBR2/TPS3 support\n");
 243                 if (!sink_tps3)
 244                         DRM_DEBUG_KMS("5.4 Gbps link rate without sink TPS3 support\n");
 245         }
 246
 247         return training_pattern;
 248 }
 249
 250 static void
 251 intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
 252 {
 253         bool channel_eq = false;
 254         int tries, cr_tries;
 255         u32 training_pattern;
 256
 257         training_pattern = intel_dp_training_pattern(intel_dp);
 258
 259         /* channel equalization */
 260         if (!intel_dp_set_link_train(intel_dp,
 261                                      training_pattern |
 262                                      DP_LINK_SCRAMBLING_DISABLE)) {
 263                 DRM_ERROR("failed to start channel equalization\n");
 264                 return;
 265         }
 266
 267         tries = 0;
 268         cr_tries = 0;
 269         channel_eq = false;
 270         for (;;) {
 271                 uint8_t link_status[DP_LINK_STATUS_SIZE];
 272
 273                 if (cr_tries > 5) {
 274                         DRM_ERROR("failed to train DP, aborting\n");
 275                         break;
 276                 }
 277
 278                 drm_dp_link_train_channel_eq_delay(intel_dp->dpcd);
 279                 if (!intel_dp_get_link_status(intel_dp, link_status)) {
 280                         DRM_ERROR("failed to get link status\n");
 281                         break;
 282                 }
 283
 284                 /* Make sure clock is still ok */
 285                 if (!drm_dp_clock_recovery_ok(link_status,
 286                                               intel_dp->lane_count)) {
 287                         intel_dp->train_set_valid = false;
 288                         intel_dp_link_training_clock_recovery(intel_dp);
 289                         intel_dp_set_link_train(intel_dp,
 290                                                 training_pattern |
 291                                                 DP_LINK_SCRAMBLING_DISABLE);
 292                         cr_tries++;
 293                         continue;
 294                 }
 295
 296                 if (drm_dp_channel_eq_ok(link_status,
 297                                          intel_dp->lane_count)) {
 298                         channel_eq = true;
 299                         break;
 300                 }
 301
 302                 /* Try 5 times, then try clock recovery if that fails */
 303                 if (tries > 5) {
 304                         intel_dp->train_set_valid = false;
 305                         intel_dp_link_training_clock_recovery(intel_dp);
 306                         intel_dp_set_link_train(intel_dp,
 307                                                 training_pattern |
 308                                                 DP_LINK_SCRAMBLING_DISABLE);
 309                         tries = 0;
 310                         cr_tries++;
 311                         continue;
 312                 }
 313
 314                 /* Update training set as requested by target */
 315                 intel_get_adjust_train(intel_dp, link_status);
 316                 if (!intel_dp_update_link_train(intel_dp)) {
 317                         DRM_ERROR("failed to update link training\n");
 318                         break;
 319                 }
 320                 ++tries;
 321         }
 322
 323         intel_dp_set_idle_link_train(intel_dp);
 324
 325         if (channel_eq) {
 326                 intel_dp->train_set_valid = true;
 327                 DRM_DEBUG_KMS("Channel EQ done. DP Training successful\n");
 328         }
 329 }
 330
 331 void intel_dp_stop_link_train(struct intel_dp *intel_dp)
 332 {
 333         intel_dp_set_link_train(intel_dp,
 334                                 DP_TRAINING_PATTERN_DISABLE);
 335 }
 336
 337 void
 338 intel_dp_start_link_train(struct intel_dp *intel_dp)
 339 {
 340         intel_dp_link_training_clock_recovery(intel_dp);
 341         intel_dp_link_training_channel_equalization(intel_dp);
 342 }