On Thu, 2016-09-01 at 15:08 -0700, Manasi Navare wrote:
> Fix the number of tries in channel euqalization link training
> sequence
> according to DP 1.2 Spec. It returns a boolean depending on channel
> equalization pass or failure.
>
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
> Signed-off-by: Manasi Navare <manasi.d.navare@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_dp_link_training.c | 57 ++++++++++-------
> ----------
> drivers/gpu/drm/i915/intel_drv.h | 1 +
> 2 files changed, 22 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c
> b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index 13a0341..07f0159 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -240,12 +240,12 @@ static u32 intel_dp_training_pattern(struct
> intel_dp *intel_dp)
> return training_pattern;
> }
>
> -static void
> +static bool
> intel_dp_link_training_channel_equalization(struct intel_dp
> *intel_dp)
> {
> - bool channel_eq = false;
> - int tries, cr_tries;
> + int tries;
> u32 training_pattern;
> + uint8_t link_status[DP_LINK_STATUS_SIZE];
>
> training_pattern = intel_dp_training_pattern(intel_dp);
>
> @@ -254,20 +254,11 @@
> intel_dp_link_training_channel_equalization(struct intel_dp
> *intel_dp)
> training_pattern |
> DP_LINK_SCRAMBLING_DISABLE)) {
> DRM_ERROR("failed to start channel equalization\n");
> - return;
> + return false;
> }
>
> - tries = 0;
> - cr_tries = 0;
> - channel_eq = false;
> - for (;;) {
> - uint8_t link_status[DP_LINK_STATUS_SIZE];
> -
> - if (cr_tries > 5) {
> - DRM_ERROR("failed to train DP, aborting\n");
> - intel_dp_dump_link_status(link_status);
> - break;
> - }
> + intel_dp->channel_eq_status = false;
> + for (tries = 0; tries < 5; tries++) {
>
> drm_dp_link_train_channel_eq_delay(intel_dp->dpcd);
> if (!intel_dp_get_link_status(intel_dp,
> link_status)) {
> @@ -278,44 +269,38 @@
> intel_dp_link_training_channel_equalization(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_link_training_clock_recovery(intel_
> dp);
> - intel_dp_set_link_train(intel_dp,
> - training_pattern |
> - DP_LINK_SCRAMBLING_D
> ISABLE);
> - cr_tries++;
> - continue;
> + intel_dp_dump_link_status(link_status);
> + DRM_DEBUG_KMS("Clock recovery check failed,
> cannot "
> + "continue channel
> equalization\n");
> + break;
> }
This clock recovery check got me thinking. Do we really need to check
if clock recovery is still ok within a loop? Could we move this outside
the loop and return early if we have failed in clock recovery? One idea
that I have in mind is that we wouldn't need to enter in channel
equalization if we have failed with clock recovery earlier.
>
> if (drm_dp_channel_eq_ok(link_status,
> intel_dp->lane_count)) {
> - channel_eq = true;
> + intel_dp->channel_eq_status = true;
> + DRM_DEBUG_KMS("Channel EQ done. DP Training
> "
> + "successful\n");
> break;
> }
>
> - /* Try 5 times, then try clock recovery if that
> fails */
> - if (tries > 5) {
> - intel_dp_link_training_clock_recovery(intel_
> dp);
> - intel_dp_set_link_train(intel_dp,
> - training_pattern |
> - DP_LINK_SCRAMBLING_D
> ISABLE);
> - tries = 0;
> - cr_tries++;
> - continue;
> - }
> -
> /* Update training set as requested by target */
> intel_get_adjust_train(intel_dp, link_status);
> if (!intel_dp_update_link_train(intel_dp)) {
> DRM_ERROR("failed to update link
> training\n");
> break;
> }
> - ++tries;
> + }
> +
> + /* Try 5 times, else fail and try at lower BW */
> + if (tries == 5) {
> + intel_dp_dump_link_status(link_status);
> + DRM_DEBUG_KMS("Channel equalization failed 5
> times\n");
> }
>
> intel_dp_set_idle_link_train(intel_dp);
>
> - if (channel_eq)
> - DRM_DEBUG_KMS("Channel EQ done. DP Training
> successful\n");
> + return intel_dp->channel_eq_status;
> +
> }
>
> void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> diff --git a/drivers/gpu/drm/i915/intel_drv.h
> b/drivers/gpu/drm/i915/intel_drv.h
> index efcd80b..e5bc976 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -878,6 +878,7 @@ struct intel_dp {
> bool link_mst;
> bool has_audio;
> bool detect_done;
> + bool channel_eq_status;
> enum hdmi_force_audio force_audio;
> bool limited_color_range;
> bool color_range_auto;
--
Mika Kahola - Intel OTC
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