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>

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 935d8cc4684190fa5c39c1d8d49b79596b4aec69..71ea0521ea96a94673752d56371516c33be84e1b 100644 (file)
--- 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;