As per DP-1.3, First check DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT. If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 1,read the DP_DP13_DPCD_REV to get the faster capability. If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 0,read DP_DPCD_REV.
Signed-off-by: Koba Ko koba.ko@canonical.com Reviewed-by: Lyude Paul lyude@redhat.com [added aux name to drm_dbg_kms() call] Signed-off-by: Lyude Paul lyude@redhat.com Link: https://patchwork.freedesktop.org/patch/msgid/20200922065313.4794-1-koba.ko@... --- drivers/gpu/drm/drm_dp_mst_topology.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 0401b2f47500..6982ecbf30b5 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -3686,9 +3686,10 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms WARN_ON(mgr->mst_primary);
/* get dpcd info */ - ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, DP_RECEIVER_CAP_SIZE); - if (ret != DP_RECEIVER_CAP_SIZE) { - DRM_DEBUG_KMS("failed to read DPCD\n"); + ret = drm_dp_read_dpcd_caps(mgr->aux, mgr->dpcd); + if (ret < 0) { + drm_dbg_kms(mgr->dev, "%s: failed to read DPCD, ret %d\n", + mgr->aux->name, ret); goto out_unlock; }