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

[ Upstream commit 4da5caa6a6f82cda3193bca855235b87debf78bd ]

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
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index e22a22baf511d79fa5b5097e3e5473c90a234fce..ef773bf58a25414bf402d6b42e6995c2619e66ed 100644 (file)
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1156,7 +1156,9 @@ 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);
                }
        }