diff options
| -rw-r--r-- | drivers/gpu/drm/drm_dp_helper.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index cb56d74e9d38..27c8c5bdf7d9 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -682,7 +682,14 @@ int drm_dp_read_downstream_info(struct drm_dp_aux *aux, !(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT)) return 0; + /* Some branches advertise having 0 downstream ports, despite also advertising they have a + * downstream port present. The DP spec isn't clear on if this is allowed or not, but since + * some branches do it we need to handle it regardless. + */ len = drm_dp_downstream_port_count(dpcd); + if (!len) + return 0; + if (dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DETAILED_CAP_INFO_AVAILABLE) len *= 4; |