Commit 9ebd8202 authored Sep 27, 2018 by Dhinakaran Pandiyan

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



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 '3cf71bc9 ("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: 3cf71bc9 ("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

parent a2bf92e8

drivers/gpu/drm/i915/intel_dp.c

+3 −10

Original line number	Original line	Diff line number	Diff line
	@@ -5074,16 +5074,9 @@ intel_dp_long_pulse(struct intel_connector *connector,
	goto out;		goto out;
	} else {		} else {
	/*		/*
	* If display is now connected check links status,		* Some external monitors do not signal loss of link
	* there has been known issues of link loss triggering		* synchronization with an IRQ_HPD, so force a link status
	* long pulse.		* check.
	*
	* 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.
	*/		*/
	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;		struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;