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* [Intel-gfx] [PATCH 1/2] drm/i915: Fix modesetting in case of unexpected AUX timeouts
@ 2021-04-12 23:24 Imre Deak
  2021-04-12 23:24 ` [Intel-gfx] [PATCH 2/2] drm/i915: Drop redundant address-of op before lttpr_common_caps array Imre Deak
                   ` (4 more replies)
  0 siblings, 5 replies; 7+ messages in thread
From: Imre Deak @ 2021-04-12 23:24 UTC (permalink / raw)
  To: intel-gfx; +Cc: stable

In case AUX failures happen unexpectedly during a modeset, the driver
should still complete the modeset. In particular the driver should
perform the link training sequence steps even in case of an AUX failure,
as this sequence also includes port initialization steps. Not doing that
can leave the port/pipe in a broken state and lead for instance to a
flip done timeout.

Fix this by continuing with link training (in a no-LTTPR mode) if the
DPRX DPCD readout failed for some reason at the beginning of link
training. After a successful connector detection we already have the
DPCD read out and cached, so the failed repeated read for it should not
cause a problem. Note that a partial AUX read could in theory partly
overwrite the cached DPCD (and return error) but this overwrite should
not happen if the returned values are corrupted (due to a timeout or
some other IO error).

Kudos to Ville to root cause the problem.

Fixes: 7dffbdedb96a ("drm/i915: Disable LTTPR support when the DPCD rev < 1.4")
References: https://gitlab.freedesktop.org/drm/intel/-/issues/3308
Cc: stable@vger.kernel.org # 5.11
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_link_training.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index 5e9c3c74310ca..cbcfb0c4c3708 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -882,7 +882,8 @@ void intel_dp_start_link_train(struct intel_dp *intel_dp,
 	int lttpr_count = intel_dp_init_lttpr_and_dprx_caps(intel_dp);
 
 	if (lttpr_count < 0)
-		return;
+		/* Still continue with enabling the port and link training. */
+		lttpr_count = 0;
 
 	if (!intel_dp_link_train_all_phys(intel_dp, crtc_state, lttpr_count))
 		intel_dp_schedule_fallback_link_training(intel_dp, crtc_state);
-- 
2.27.0

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^ permalink raw reply related	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-04-13 17:13 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2021-04-12 23:24 [Intel-gfx] [PATCH 1/2] drm/i915: Fix modesetting in case of unexpected AUX timeouts Imre Deak
2021-04-12 23:24 ` [Intel-gfx] [PATCH 2/2] drm/i915: Drop redundant address-of op before lttpr_common_caps array Imre Deak
2021-04-13 17:13   ` Ville Syrjälä
2021-04-12 23:48 ` [Intel-gfx] ✗ Fi.CI.DOCS: warning for series starting with [1/2] drm/i915: Fix modesetting in case of unexpected AUX timeouts Patchwork
2021-04-13  0:11 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2021-04-13  1:29 ` [Intel-gfx] ✗ Fi.CI.IGT: failure " Patchwork
2021-04-13 17:12 ` [Intel-gfx] [PATCH 1/2] " Ville Syrjälä

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