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drm/i915/dp: Fix link retraining comment in intel_dp_long_pulse()

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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: 3cf71bc990 ("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>
Link: https://patchwork.freedesktop.org/patch/msgid/20180927205735.16651-1-dhinakaran.pandiyan@intel.com
This commit is contained in:
Dhinakaran Pandiyan 2018-09-27 13:57:30 -07:00
parent a2bf92e8cc
commit 9ebd820239
1 changed files with 3 additions and 10 deletions
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13
drivers/gpu/drm/i915/intel_dp.c
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@ -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;