drm/dp/mst: Check peer device type before attempting EDID read

Only certain types of pdts have the DDC bus registered, so check for
that before we attempt the EDID read. Othwewise we risk playing around
with an i2c adapter that doesn't actually exist.

Cc: stable@vger.kernel.org
Cc: Carlos Santa <carlos.santa@intel.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Tested-by: Carlos Santa <carlos.santa@intel.com>
Tested-by: Kirill A. Shutemov <kirill@shutemov.name>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97666
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1477472755-15288-5-git-send-email-ville.syrjala@linux.intel.com

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index ba13f9d8720b950ee3fc2130133d50caff99ce82..aa644487749c9cbab104f2ea77c819baf7d6b250 100644 (file)
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1160,7 +1160,9 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
                        drm_dp_put_port(port);
                        goto out;
                }
-               if (port->port_num >= DP_MST_LOGICAL_PORT_0) {
+               if ((port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV ||
+                    port->pdt == DP_PEER_DEVICE_SST_SINK) &&
+                   port->port_num >= DP_MST_LOGICAL_PORT_0) {
                        port->cached_edid = drm_get_edid(port->connector, &port->aux.ddc);
                        drm_mode_connector_set_tile_property(port->connector);
                }