This is a note to let you know that I've just added the patch titled drm/i915/dp: Fix link retraining comment in intel_dp_long_pulse() to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-i915-dp-fix-link-retraining-comment-in-intel_dp_long_pulse.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 49af5d95b9b3c21a84ad115a9db9acbc036d849a Mon Sep 17 00:00:00 2001 From: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx> Date: Thu, 27 Sep 2018 13:57:30 -0700 Subject: drm/i915/dp: Fix link retraining comment in intel_dp_long_pulse() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx> commit 49af5d95b9b3c21a84ad115a9db9acbc036d849a upstream. 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@xxxxxxxxxx> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> Cc: Jan-Marek Glogowski <glogow@xxxxxxxxxx> References: 3cf71bc9904d ("drm/i915: Re-apply "Perform link quality check, unconditionally during long pulse"") Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx> Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20180927205735.16651-1-dhinakaran.pandiyan@xxxxxxxxx (cherry picked from commit 9ebd8202393dde9d3678c9ec162c1aa63ba17eac) Fixes: 399334708b4f ("drm/i915: Re-apply "Perform link quality check, unconditionally during long pulse"") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/i915/intel_dp.c | 13 +++---------- 1 file changed, 3 insertions(+), 10 deletions(-) --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -4741,16 +4741,9 @@ intel_dp_long_pulse(struct intel_connect 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; Patches currently in stable-queue which might be from dhinakaran.pandiyan@xxxxxxxxx are queue-4.19/drm-i915-dp-restrict-link-retrain-workaround-to-external-monitors.patch queue-4.19/drm-i915-dp-fix-link-retraining-comment-in-intel_dp_long_pulse.patch