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drm/i915: eDP link training optimization

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This is a first of series patches that optimize DP link
training. The first patch is for eDP only where we reuse
the previously trained link training values from cache
i.e. voltage swing and pre-emphasis levels.

In case we are not able to train the link by reusing
the known values, the link training parameters are set
to zero and training is restarted.

V2:
- flag that indicates if DP link is trained and valid
  renamed from 'link_trained' to 'train_set_valid'
- removed routine 'intel_dp_reuse_link_train'

V3:
- rebased against the latest drm-intel-nightly

V4:
- removed HPD long pulse handling for eDP case to clear the
  flag that indicates to reuse the current link training
  parameters. (based on Sivakumar's comment)

Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>
[danvet: s/DP/eDP/ in subject to make scope clear.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Mika Kahola 2015-04-29 09:17:39 +03:00 committed by Daniel Vetter
parent 3ef62342bd
commit 4e96c97742
2 changed files with 25 additions and 3 deletions
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27
drivers/gpu/drm/i915/intel_dp.c
View File

@ -3547,7 +3547,8 @@ static bool
intel_dp_reset_link_train(struct intel_dp *intel_dp, uint32_t *DP,
uint8_t dp_train_pat)
{
memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
if (!intel_dp->train_set_valid)
memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
intel_dp_set_signal_levels(intel_dp, DP);
return intel_dp_set_link_train(intel_dp, DP, dp_train_pat);
}
@ -3660,6 +3661,23 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
break;
}
/*
* if we used previously trained voltage and pre-emphasis values
* and we don't get clock recovery, reset link training values
*/
if (intel_dp->train_set_valid) {
DRM_DEBUG_KMS("clock recovery not ok, reset");
/* clear the flag as we are not reusing train set */
intel_dp->train_set_valid = false;
if (!intel_dp_reset_link_train(intel_dp, &DP,
DP_TRAINING_PATTERN_1 |
DP_LINK_SCRAMBLING_DISABLE)) {
DRM_ERROR("failed to enable link training\n");
return;
}
continue;
}
/* Check to see if we've tried the max voltage */
for (i = 0; i < intel_dp->lane_count; i++)
if ((intel_dp->train_set[i] & DP_TRAIN_MAX_SWING_REACHED) == 0)
@ -3737,6 +3755,7 @@ intel_dp_complete_link_train(struct intel_dp *intel_dp)
/* Make sure clock is still ok */
if (!drm_dp_clock_recovery_ok(link_status, intel_dp->lane_count)) {
intel_dp->train_set_valid = false;
intel_dp_start_link_train(intel_dp);
intel_dp_set_link_train(intel_dp, &DP,
training_pattern |
@ -3752,6 +3771,7 @@ intel_dp_complete_link_train(struct intel_dp *intel_dp)
/* Try 5 times, then try clock recovery if that fails */
if (tries > 5) {
intel_dp->train_set_valid = false;
intel_dp_start_link_train(intel_dp);
intel_dp_set_link_train(intel_dp, &DP,
training_pattern |
@ -3773,9 +3793,10 @@ intel_dp_complete_link_train(struct intel_dp *intel_dp)
intel_dp->DP = DP;
if (channel_eq)
if (channel_eq) {
intel_dp->train_set_valid = is_edp(intel_dp);
DRM_DEBUG_KMS("Channel EQ done. DP Training successful\n");
}
}
void intel_dp_stop_link_train(struct intel_dp *intel_dp)

1
drivers/gpu/drm/i915/intel_drv.h
View File

@ -736,6 +736,7 @@ struct intel_dp {
bool has_aux_irq,
int send_bytes,
uint32_t aux_clock_divider);
bool train_set_valid;
/* Displayport compliance testing */
unsigned long compliance_test_type;