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List:       git-commits-head
Subject:    drm/dp/mst: Restore primary hub guid on resume
From:       "Linux Kernel Mailing List" <linux-kernel () vger ! kernel ! org>
Date:       2016-04-30 0:48:59
Message-ID: 20160430004859.6216B660F6A () gitolite ! kernel ! org
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Web:        https://git.kernel.org/torvalds/c/9dc0487d96a0396367a1451b31873482080b527f
Commit:     9dc0487d96a0396367a1451b31873482080b527f
Parent:     263efde31f97c498e1ebad30e4d2906609d7ad6b
Refname:    refs/heads/master
Author:     Lyude <cpaul@redhat.com>
AuthorDate: Wed Apr 13 16:50:18 2016 -0400
Committer:  Dave Airlie <airlied@redhat.com>
CommitDate: Wed Apr 27 09:29:40 2016 +1000

    drm/dp/mst: Restore primary hub guid on resume
    
    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
    Cc: stable@vger.kernel.org
    Signed-off-by: Dave Airlie <airlied@redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 935d8cc..71ea052 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2136,6 +2136,8 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr)
 
 	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");
@@ -2150,6 +2152,16 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr)
 			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;
--
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