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

BugLink: http://bugs.launchpad.net/bugs/1578798
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 73eb7ce0926dc21a71648175da8e71ee9e38b17a..468d6014157fd85b6ec85b161b9bad2d74896c33 100644 (file)
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2126,6 +2126,8 @@ 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");
@@ -2140,6 +2142,16 @@ 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;