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         memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
  89         intel_dp_set_signal_levels(intel_dp);
  90         return intel_dp_set_link_train(intel_dp, dp_train_pat);
  91 }
  92
  93 static bool
  94 intel_dp_update_link_train(struct intel_dp *intel_dp)
  95 {
  96         int ret;
  97
  98         intel_dp_set_signal_levels(intel_dp);
  99
 100         ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_LANE0_SET,
 101                                 intel_dp->train_set, intel_dp->lane_count);
 102
 103         return ret == intel_dp->lane_count;
 104 }
 105
 106 /* Enable corresponding port and start training pattern 1 */
 107 static void
 108 intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
 109 {
 110         int i;
 111         uint8_t voltage;
 112         int voltage_tries, loop_tries;
 113         uint8_t link_config[2];
 114         uint8_t link_bw, rate_select;
 115
 116         if (intel_dp->prepare_link_retrain)
 117                 intel_dp->prepare_link_retrain(intel_dp);
 118
 119         intel_dp_compute_rate(intel_dp, intel_dp->link_rate,
 120                               &link_bw, &rate_select);
 121
 122         /* Write the link configuration data */
 123         link_config[0] = link_bw;
 124         link_config[1] = intel_dp->lane_count;
 125         if (drm_dp_enhanced_frame_cap(intel_dp->dpcd))
 126                 link_config[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
 127         drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, 2);
 128         if (intel_dp->num_sink_rates)
 129                 drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_RATE_SET,
 130                                   &rate_select, 1);
 131
 132         link_config[0] = 0;
 133         link_config[1] = DP_SET_ANSI_8B10B;
 134         drm_dp_dpcd_write(&intel_dp->aux, DP_DOWNSPREAD_CTRL, link_config, 2);
 135
 136         intel_dp->DP |= DP_PORT_EN;
 137
 138         /* clock recovery */
 139         if (!intel_dp_reset_link_train(intel_dp,
 140                                        DP_TRAINING_PATTERN_1 |
 141                                        DP_LINK_SCRAMBLING_DISABLE)) {
 142                 DRM_ERROR("failed to enable link training\n");
 143                 return;
 144         }
 145
 146         voltage = 0xff;
 147         voltage_tries = 0;
 148         loop_tries = 0;
 149         for (;;) {
 150                 uint8_t link_status[DP_LINK_STATUS_SIZE];
 151
 152                 drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
 153                 if (!intel_dp_get_link_status(intel_dp, link_status)) {
 154                         DRM_ERROR("failed to get link status\n");
 155                         break;
 156                 }
 157
 158                 if (drm_dp_clock_recovery_ok(link_status, intel_dp->lane_count)) {
 159                         DRM_DEBUG_KMS("clock recovery OK\n");
 160                         break;
 161                 }
 162
 163                 /* Check to see if we've tried the max voltage */
 164                 for (i = 0; i < intel_dp->lane_count; i++)
 165                         if ((intel_dp->train_set[i] & DP_TRAIN_MAX_SWING_REACHED) == 0)
 166                                 break;
 167                 if (i == intel_dp->lane_count) {
 168                         ++loop_tries;
 169                         if (loop_tries == 5) {
 170                                 DRM_ERROR("too many full retries, give up\n");
 171                                 break;
 172                         }
 173                         intel_dp_reset_link_train(intel_dp,
 174                                                   DP_TRAINING_PATTERN_1 |
 175                                                   DP_LINK_SCRAMBLING_DISABLE);
 176                         voltage_tries = 0;
 177                         continue;
 178                 }
 179
 180                 /* Check to see if we've tried the same voltage 5 times */
 181                 if ((intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK) == voltage) {
 182                         ++voltage_tries;
 183                         if (voltage_tries == 5) {
 184                                 DRM_ERROR("too many voltage retries, give up\n");
 185                                 break;
 186                         }
 187                 } else
 188                         voltage_tries = 0;
 189                 voltage = intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK;
 190
 191                 /* Update training set as requested by target */
 192                 intel_get_adjust_train(intel_dp, link_status);
 193                 if (!intel_dp_update_link_train(intel_dp)) {
 194                         DRM_ERROR("failed to update link training\n");
 195                         break;
 196                 }
 197         }
 198 }
 199
 200 /*
 201  * Pick training pattern for channel equalization. Training Pattern 3 for HBR2
 202  * or 1.2 devices that support it, Training Pattern 2 otherwise.
 203  */
 204 static u32 intel_dp_training_pattern(struct intel_dp *intel_dp)
 205 {
 206         u32 training_pattern = DP_TRAINING_PATTERN_2;
 207         bool source_tps3, sink_tps3;
 208
 209         /*
 210          * Intel platforms that support HBR2 also support TPS3. TPS3 support is
 211          * also mandatory for downstream devices that support HBR2. However, not
 212          * all sinks follow the spec.
 213          *
 214          * Due to WaDisableHBR2 SKL < B0 is the only exception where TPS3 is
 215          * supported in source but still not enabled.
 216          */
 217         source_tps3 = intel_dp_source_supports_hbr2(intel_dp);
 218         sink_tps3 = drm_dp_tps3_supported(intel_dp->dpcd);
 219
 220         if (source_tps3 && sink_tps3) {
 221                 training_pattern = DP_TRAINING_PATTERN_3;
 222         } else if (intel_dp->link_rate == 540000) {
 223                 if (!source_tps3)
 224                         DRM_DEBUG_KMS("5.4 Gbps link rate without source HBR2/TPS3 support\n");
 225                 if (!sink_tps3)
 226                         DRM_DEBUG_KMS("5.4 Gbps link rate without sink TPS3 support\n");
 227         }
 228
 229         return training_pattern;
 230 }
 231
 232 static void
 233 intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
 234 {
 235         bool channel_eq = false;
 236         int tries, cr_tries;
 237         u32 training_pattern;
 238
 239         training_pattern = intel_dp_training_pattern(intel_dp);
 240
 241         /* channel equalization */
 242         if (!intel_dp_set_link_train(intel_dp,
 243                                      training_pattern |
 244                                      DP_LINK_SCRAMBLING_DISABLE)) {
 245                 DRM_ERROR("failed to start channel equalization\n");
 246                 return;
 247         }
 248
 249         tries = 0;
 250         cr_tries = 0;
 251         channel_eq = false;
 252         for (;;) {
 253                 uint8_t link_status[DP_LINK_STATUS_SIZE];
 254
 255                 if (cr_tries > 5) {
 256                         DRM_ERROR("failed to train DP, aborting\n");
 257                         break;
 258                 }
 259
 260                 drm_dp_link_train_channel_eq_delay(intel_dp->dpcd);
 261                 if (!intel_dp_get_link_status(intel_dp, link_status)) {
 262                         DRM_ERROR("failed to get link status\n");
 263                         break;
 264                 }
 265
 266                 /* Make sure clock is still ok */
 267                 if (!drm_dp_clock_recovery_ok(link_status,
 268                                               intel_dp->lane_count)) {
 269                         intel_dp_link_training_clock_recovery(intel_dp);
 270                         intel_dp_set_link_train(intel_dp,
 271                                                 training_pattern |
 272                                                 DP_LINK_SCRAMBLING_DISABLE);
 273                         cr_tries++;
 274                         continue;
 275                 }
 276
 277                 if (drm_dp_channel_eq_ok(link_status,
 278                                          intel_dp->lane_count)) {
 279                         channel_eq = true;
 280                         break;
 281                 }
 282
 283                 /* Try 5 times, then try clock recovery if that fails */
 284                 if (tries > 5) {
 285                         intel_dp_link_training_clock_recovery(intel_dp);
 286                         intel_dp_set_link_train(intel_dp,
 287                                                 training_pattern |
 288                                                 DP_LINK_SCRAMBLING_DISABLE);
 289                         tries = 0;
 290                         cr_tries++;
 291                         continue;
 292                 }
 293
 294                 /* Update training set as requested by target */
 295                 intel_get_adjust_train(intel_dp, link_status);
 296                 if (!intel_dp_update_link_train(intel_dp)) {
 297                         DRM_ERROR("failed to update link training\n");
 298                         break;
 299                 }
 300                 ++tries;
 301         }
 302
 303         intel_dp_set_idle_link_train(intel_dp);
 304
 305         if (channel_eq)
 306                 DRM_DEBUG_KMS("Channel EQ done. DP Training successful\n");
 307 }
 308
 309 void intel_dp_stop_link_train(struct intel_dp *intel_dp)
 310 {
 311         intel_dp_set_link_train(intel_dp,
 312                                 DP_TRAINING_PATTERN_DISABLE);
 313 }
 314
 315 void
 316 intel_dp_start_link_train(struct intel_dp *intel_dp)
 317 {
 318         intel_dp_link_training_clock_recovery(intel_dp);
 319         intel_dp_link_training_channel_equalization(intel_dp);
 320 }