Patch "drm/dp/mst: Restore primary hub guid on resume" has been added to the 4.4-stable tree

Patch "drm/dp/mst: Restore primary hub guid on resume" has been added to the 4.4-stable tree

[gregkh]

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

    drm/dp/mst: Restore primary hub guid on resume

to the 4.4-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-dp-mst-restore-primary-hub-guid-on-resume.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 9dc0487d96a0396367a1451b31873482080b527f Mon Sep 17 00:00:00 2001
From: Lyude <cpaul@redhat.com>
Date: Wed, 13 Apr 2016 16:50:18 -0400
Subject: drm/dp/mst: Restore primary hub guid on resume

From: Lyude <cpaul@redhat.com>

commit 9dc0487d96a0396367a1451b31873482080b527f upstream.

Some hubs are forgetful, and end up forgetting whatever GUID we set
previously after we do a suspend/resume cycle. This can lead to
hotplugging breaking (along with probably other things) since the hub
will start sending connection notifications with the wrong GUID. As
such, we need to check on resume whether or not the GUID the hub is
giving us is valid.

Signed-off-by: Lyude <cpaul@redhat.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1460580618-7421-1-git-send-email-cpaul@redhat.com
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/drm_dp_mst_topology.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2116,6 +2116,8 @@ int drm_dp_mst_topology_mgr_resume(struc
 
 	if (mgr->mst_primary) {
 		int sret;
+		u8 guid[16];
+
 		sret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, DP_RECEIVER_CAP_SIZE);
 		if (sret != DP_RECEIVER_CAP_SIZE) {
 			DRM_DEBUG_KMS("dpcd read failed - undocked during suspend?\n");
@@ -2130,6 +2132,16 @@ int drm_dp_mst_topology_mgr_resume(struc
 			ret = -1;
 			goto out_unlock;
 		}
+
+		/* Some hubs forget their guids after they resume */
+		sret = drm_dp_dpcd_read(mgr->aux, DP_GUID, guid, 16);
+		if (sret != 16) {
+			DRM_DEBUG_KMS("dpcd read failed - undocked during suspend?\n");
+			ret = -1;
+			goto out_unlock;
+		}
+		drm_dp_check_mstb_guid(mgr->mst_primary, guid);
+
 		ret = 0;
 	} else
 		ret = -1;


Patches currently in stable-queue which might be from cpaul@redhat.com are

queue-4.4/drm-dp-mst-restore-primary-hub-guid-on-resume.patch
queue-4.4/drm-dp-mst-validate-port-in-drm_dp_payload_send_msg.patch
queue-4.4/drm-i915-fix-race-condition-in-intel_dp_destroy_mst_connector.patch
queue-4.4/drm-dp-mst-get-validated-port-ref-in-drm_dp_update_payload_part1.patch