From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Wed, 17 Jan 2018 21:21:49 +0200
Subject: drm/i915: Track whether the DP link is trained or not
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Git-commit: edb2e5301c4489d8c99b0f3d86a074df27f6f8ff
Patch-mainline: v4.17-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

LSPCON likes to throw short HPDs during the enable seqeunce prior to the
link being trained. These obviously result in the channel CR/EQ check
failing and thus we schedule a pointless hotplug work to retrain the
link. Avoid that by ignoring the bad CR/EQ status until we've actually
initially trained the link.

I've not actually investigated to see what LSPCON is trying to signal
with the short pulse. But as long as it signals anything I think we're
supposed to check the link status anyway, so I don't really see other
good ways to solve this. I've not seen these short pulses being
generated by normal DP sinks.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180117192149.17760-5-ville.syrjala@linux.intel.com

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/i915/intel_ddi.c              |    2 ++
 drivers/gpu/drm/i915/intel_dp.c               |   10 +++++++---
 drivers/gpu/drm/i915/intel_dp_link_training.c |    2 ++
 drivers/gpu/drm/i915/intel_drv.h              |    1 +
 4 files changed, 12 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -2505,6 +2505,8 @@ static void intel_disable_ddi_dp(struct
 {
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
 
+	intel_dp->link_trained = false;
+
 	if (old_crtc_state->has_audio)
 		intel_audio_codec_disable(encoder,
 					  old_crtc_state, old_conn_state);
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1913,6 +1913,7 @@ void intel_dp_set_link_params(struct int
 			      int link_rate, uint8_t lane_count,
 			      bool link_mst)
 {
+	intel_dp->link_trained = false;
 	intel_dp->link_rate = link_rate;
 	intel_dp->lane_count = lane_count;
 	intel_dp->link_mst = link_mst;
@@ -2761,6 +2762,8 @@ static void intel_disable_dp(struct inte
 {
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
 
+	intel_dp->link_trained = false;
+
 	if (old_crtc_state->has_audio)
 		intel_audio_codec_disable(encoder,
 					  old_crtc_state, old_conn_state);
@@ -4277,10 +4280,11 @@ intel_dp_needs_link_retrain(struct intel
 {
 	u8 link_status[DP_LINK_STATUS_SIZE];
 
-	if (!intel_dp_get_link_status(intel_dp, link_status)) {
-		DRM_ERROR("Failed to get link status\n");
+	if (!intel_dp->link_trained)
+		return false;
+
+	if (!intel_dp_get_link_status(intel_dp, link_status))
 		return false;
-	}
 
 	/*
 	 * Validate the cached values of intel_dp->link_rate and
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -307,6 +307,8 @@ intel_dp_link_training_channel_equalizat
 
 void intel_dp_stop_link_train(struct intel_dp *intel_dp)
 {
+	intel_dp->link_trained = true;
+
 	intel_dp_set_link_train(intel_dp,
 				DP_TRAINING_PATTERN_DISABLE);
 }
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1048,6 +1048,7 @@ struct intel_dp {
 	uint8_t lane_count;
 	uint8_t sink_count;
 	bool link_mst;
+	bool link_trained;
 	bool has_audio;
 	bool detect_done;
 	bool reset_link_params;