[PATCH AUTOSEL 5.6 130/606] drm/amd/display: Prevent dpcd reads with passive dongles

Sasha Levin
2020-06-09T00:34:02Z

From: Aurabindo Pillai <aurabindo.pillai@amd.com>

[ Upstream commit e6142dd511425cb827b5db869f489eb81f5f994d ]

[why]
During hotplug, a DP port may be connected to the sink through
passive adapter which does not support DPCD reads. Issuing reads
without checking for this condition will result in errors

[how]
Ensure the link is in aux_mode before initiating operation that result
in a DPCD read.

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 5e27a67fbc58..0cd11d3d4cf4 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -1941,17 +1941,22 @@ amdgpu_dm_update_connector_after_detect(struct amdgpu_dm_connector *aconnector)
dc_sink_retain(aconnector->dc_sink);
if (sink->dc_edid.length == 0) {
aconnector->edid = NULL;
- drm_dp_cec_unset_edid(&aconnector->dm_dp_aux.aux);
+ if (aconnector->dc_link->aux_mode) {
+ drm_dp_cec_unset_edid(
+ &aconnector->dm_dp_aux.aux);
+ }
} else {
aconnector->edid =
- (struct edid *) sink->dc_edid.raw_edid;
-
+ (struct edid *)sink->dc_edid.raw_edid;

drm_connector_update_edid_property(connector,
- aconnector->edid);
- drm_dp_cec_set_edid(&aconnector->dm_dp_aux.aux,
- aconnector->edid);
+ aconnector->edid);
+
+ if (aconnector->dc_link->aux_mode)
+ drm_dp_cec_set_edid(&aconnector->dm_dp_aux.aux,
+ aconnector->edid);
}
+
amdgpu_dm_update_freesync_caps(connector, aconnector->edid);

} else {
--
2.25.1