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Commit bfd02b3c authored by Ville Syrjälä's avatar Ville Syrjälä
Browse files

drm/i915: Suppress underruns during DP link retraining 

DP link retraining causes (spurious?) underruns. We can't really avoid
them, except perhaps by doing a full modeset (which has its own underrun
suppression anyway). So let's just hide them.

MST still has its own logic for retrainin, but a bigger hpd handling
cleanup/unification is needed there anyway, so let's leave that be for now.

References: https://bugs.freedesktop.org/show_bug.cgi?id=98251


Signed-off-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1476464574-32230-3-git-send-email-ville.syrjala@linux.intel.com


Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
parent 65f2130c

drivers/gpu/drm/i915/intel_dp.c

+27 −2
Original line number Diff line number Diff line
@@ -3987,6 +3987,31 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp) 
	return -EINVAL;

}



static void

intel_dp_retrain_link(struct intel_dp *intel_dp)

{

	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;

	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);

	struct intel_crtc *crtc = to_intel_crtc(encoder->base.crtc);



	/* Suppress underruns caused by re-training */

	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe, false);

	if (crtc->config->has_pch_encoder)

		intel_set_pch_fifo_underrun_reporting(dev_priv,

						      intel_crtc_pch_transcoder(crtc), false);



	intel_dp_start_link_train(intel_dp);

	intel_dp_stop_link_train(intel_dp);



	/* Keep underrun reporting disabled until things are stable */

	intel_wait_for_vblank(&dev_priv->drm, crtc->pipe);



	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe, true);

	if (crtc->config->has_pch_encoder)

		intel_set_pch_fifo_underrun_reporting(dev_priv,

						      intel_crtc_pch_transcoder(crtc), true);

}



static void

intel_dp_check_link_status(struct intel_dp *intel_dp)

{
@@ -4012,8 +4037,8 @@ intel_dp_check_link_status(struct intel_dp *intel_dp) 
	    (!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count))) {

		DRM_DEBUG_KMS("%s: channel EQ not ok, retraining\n",

			      intel_encoder->base.name);

		intel_dp_start_link_train(intel_dp);

		intel_dp_stop_link_train(intel_dp);



		intel_dp_retrain_link(intel_dp);

	}

}