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

[ Upstream commit 9dc0487d96a0396367a1451b31873482080b527f ]

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>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index e174fceac379e208a1651dabb94a40495068e3b4..c4f8e8f172cd991999b2bb7012ad9eb0474989b8 100644 (file)
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2013,6 +2013,8 @@ 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");
@@ -2027,6 +2029,16 @@ 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;