[CI 1/6] drm/i915/dp: Fix link retraining comment in intel_dp_long_pulse()

From: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
To: intel-gfx@lists.freedesktop.org
Subject: [CI 1/6] drm/i915/dp: Fix link retraining comment in intel_dp_long_pulse()
Date: Thu, 27 Sep 2018 13:57:30 -0700	[thread overview]
Message-ID: <20180927205735.16651-1-dhinakaran.pandiyan@intel.com> (raw)

Comment claims link needs to be retrained because the connected sink raised
a long pulse to indicate link loss. If the sink did so,
intel_dp_hotplug() would have handled link retraining. Looking at the
logs in Bugzilla referenced in commit '3cf71bc9904d ("drm/i915: Re-apply
Perform link quality check, unconditionally during long pulse"")', the
issue is that the sink does not trigger an interrupt. What we want is
->detect() from user space to check link status and retrain. Ville's
review for the original patch also indicates the same root cause. So,
rewrite the comment.

v2: Patch split and rewrote comment.

Cc: Lyude Paul <lyude@redhat.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jan-Marek Glogowski <glogow@fbihome.de>
References: 3cf71bc9904d ("drm/i915: Re-apply "Perform link quality check, unconditionally during long pulse"")
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 256a71c8c093..207b3ea2ed1a 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -5074,16 +5074,9 @@ intel_dp_long_pulse(struct intel_connector *connector,
 		goto out;
 	} else {
 		/*
-		 * If display is now connected check links status,
-		 * there has been known issues of link loss triggering
-		 * long pulse.
-		 *
-		 * Some sinks (eg. ASUS PB287Q) seem to perform some
-		 * weird HPD ping pong during modesets. So we can apparently
-		 * end up with HPD going low during a modeset, and then
-		 * going back up soon after. And once that happens we must
-		 * retrain the link to get a picture. That's in case no
-		 * userspace component reacted to intermittent HPD dip.
+		 * Some external monitors do not signal loss of link
+		 * synchronization with an IRQ_HPD, so force a link status
+		 * check.
 		 */
 		struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
 
-- 
2.17.1

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