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