Patch "drm/i915: Check DP link status on long hpd too" has been added to the 4.2-stable tree

This is a note to let you know that I've just added the patch titled

drm/i915: Check DP link status on long hpd too

to the 4.2-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-check-dp-link-status-on-long-hpd-too.patch

and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <[email protected]>
Date: Thu, 20 Aug 2015 19:37:29 +0300
Subject: drm/i915: Check DP link status on long hpd too
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From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <[email protected]>

commit d14e7b6d1d8747826cb900db852351c550e00fdd upstream.

We are no longer checkling the DP link status on long hpd. We used to do that from the .hot_plug() handler, but it was removed when MST got introduced.

If there's no userspace we now fail to retrain the link if the sink power is toggled (or cable yanked and replugged), meaning the user is left staring at a blank screen. With the retraining put back that should be fixed.

Also remove the leftover comment that referred to the old retraining from .hot_plug().

Fixes a regression introduced in:
commit 0e32b39ceed665bfa4a77a4bc307b6652b991632

Author: Dave Airlie <[email protected]>
Date:   Fri May 2 14:02:48 2014 +1000

    drm/i915: add DP 1.2 MST support (v0.7)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89453

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91407
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89461
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89594
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=85641

---
 drivers/gpu/drm/i915/intel_dp.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

@@ -4987,9 +4987,12 @@ intel_dp_hpd_pulse(struct intel_digital_
 
 		intel_dp_probe_oui(intel_dp);
 
-		if (!intel_dp_probe_mst(intel_dp))
+		if (!intel_dp_probe_mst(intel_dp)) {
+			drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+			intel_dp_check_link_status(intel_dp);
+			drm_modeset_unlock(&dev->mode_config.connection_mutex);
 			goto mst_fail;
-
+		}
 	} else {
 		if (intel_dp->is_mst) {
 			if (intel_dp_check_mst_status(intel_dp) == -EINVAL)

@@ -4997,10 +5000,6 @@ intel_dp_hpd_pulse(struct intel_digital_
 		}
 
 		if (!intel_dp->is_mst) {
-			/*
-			 * we'll check the link status via the normal hot plug path later -
-			 * but for short hpds we should check it now
-			 */
 			drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
 			intel_dp_check_link_status(intel_dp);
 			drm_modeset_unlock(&dev->mode_config.connection_mutex);

Patches currently in stable-queue which might be from [email protected] are

queue-4.2/drm-i915-check-dp-link-status-on-long-hpd-too.patch