Re: [PATCH v3 5/5] drm/i915: Implement proper fallback training for MST

Ville Syrjälä
2018-03-12T21:12:26Z

On Fri, Mar 09, 2018 at 04:32:31PM -0500, Lyude Paul wrote:
> @@ -6266,25 +6368,98 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> return false;
> }
>
> +static void intel_dp_mst_retrain_link_work(struct work_struct *work)
> +{

Why do we need another work for this? Can't we just retrain from the
hotplug work always?

> + struct drm_modeset_acquire_ctx ctx;
> + struct intel_dp *intel_dp = container_of(work, typeof(*intel_dp),
> + mst_retrain_work);
> + struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
> + struct drm_device *dev = intel_encoder->base.dev;
> + int ret;
> + bool had_error = false;
> +
> + drm_modeset_acquire_init(&ctx, 0);
> +
> + for (;;) {
> + ret = intel_dp_retrain_link(intel_encoder, &ctx);
> + if (ret == -EDEADLK) {
> + drm_modeset_backoff(&ctx);
> + continue;
> + }
> +
> + break;
> + }
> + if (!ret) {
> + DRM_DEBUG_KMS("Retrain complete\n");
> + goto out;
> + } else if (ret == -EIO) {
> + DRM_ERROR("IO error with sink during retrain? Aborting\n");
> + had_error = true;
> + goto out;
> + }
> +
> + DRM_DEBUG_KMS("Retraining failed with %d, marking link status as bad\n",
> + ret);
> +
> + /* We ran out of retries, if the sink hasn't changed the link rate in
> + * it's dpcd yet force us to fallback to a lower link rate/count */
> + if (ret == -EINVAL) {
> + ret = intel_dp_get_dpcd(intel_dp);
> + if (!ret) {
> + DRM_ERROR("IO error while reading dpcd from sink\n");
> + had_error = true;
> + goto out;
> + }
> +
> + if (intel_dp->link_rate == intel_dp_max_link_rate(intel_dp) &&
> + intel_dp->lane_count == intel_dp_max_lane_count(intel_dp)) {
> + intel_dp_get_link_train_fallback_values(
> + intel_dp, intel_dp_max_link_rate(intel_dp),
> + intel_dp_max_lane_count(intel_dp));
> + }
> + }
> +
> + intel_dp->mst_link_is_bad = true;
> + intel_dp->mst_bw_locked = false;
> + schedule_work(&intel_dp->modeset_retry_work);
> +out:
> + drm_modeset_drop_locks(&ctx);
> + drm_modeset_acquire_fini(&ctx);
> + if (had_error)
> + drm_kms_helper_hotplug_event(dev);
> +}
> +

--
Ville Syrjälä
Intel OTC
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