[PATCH 5/7][SRU][OEM-B][B] drm/i915: Track whether the DP link is trained or not

[You-Sheng Yang]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

BugLink: http://bugs.launchpad.net/bugs/1835001

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 at linux.intel.com>
Reviewed-by: Lyude Paul <lyude at redhat.com>
Signed-off-by: Lyude Paul <lyude at redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180117192149.17760-5-ville.syrjala@linux.intel.com
(cherry picked from commit edb2e5301c4489d8c99b0f3d86a074df27f6f8ff)
Signed-off-by: You-Sheng Yang <vicamo.yang at canonical.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(-)

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 04b2ed81d805..123e400abf9b 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -2455,6 +2455,8 @@ static void intel_disable_ddi_dp(struct intel_encoder *encoder,
 {
 	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);
 
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 8fb9a1cbfb96..b9813e1d9229 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1826,6 +1826,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
 			      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;
@@ -2664,6 +2665,8 @@ static void intel_disable_dp(struct intel_encoder *encoder,
 {
 	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);
 
@@ -4247,10 +4250,11 @@ intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
 {
 	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
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index 1314f5d87d7d..78f1fe934da3 100644
--- 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_equalization(struct intel_dp *intel_dp)
 
 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);
 }
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index cede0f93de39..4e05a94ddf24 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -962,6 +962,7 @@ 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;
-- 
2.20.1