4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Lyude <cp...@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 <cp...@redhat.com> Reviewed-by: Harry Wentland <harry.wentl...@amd.com> Signed-off-by: Daniel Vetter <daniel.vet...@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1460580618-7421-1-git-send-email-cp...@redhat.com Signed-off-by: Dave Airlie <airl...@redhat.com> Signed-off-by: Greg Kroah-Hartman <gre...@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;
