[PATCH AUTOSEL 6.10 19/34] drm/amd/display: Don't refer to dc_sink in is_dsc_need_re_compute

Sasha Levin
2024-07-28T15:44:27Z

From: Wayne Lin <wayne.lin@amd.com>

[ Upstream commit fcf6a49d79923a234844b8efe830a61f3f0584e4 ]

[Why]
When unplug one of monitors connected after mst hub, encounter null pointer dereference.

It's due to dc_sink get released immediately in early_unregister() or detect_ctx(). When
commit new state which directly referring to info stored in dc_sink will cause null pointer
dereference.

[how]
Remove redundant checking condition. Relevant condition should already be covered by checking
if dsc_aux is null or not. Also reset dsc_aux to NULL when the connector is disconnected.

Reviewed-by: Jerry Zuo <jerry.zuo@amd.com>
Acked-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index a5e1a93ddaea2..025938409145a 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -182,6 +182,8 @@ amdgpu_dm_mst_connector_early_unregister(struct drm_connector *connector)
dc_sink_release(dc_sink);
aconnector->dc_sink = NULL;
aconnector->edid = NULL;
+ aconnector->dsc_aux = NULL;
+ port->passthrough_aux = NULL;
}

aconnector->mst_status = MST_STATUS_DEFAULT;
@@ -494,6 +496,8 @@ dm_dp_mst_detect(struct drm_connector *connector,
dc_sink_release(aconnector->dc_sink);
aconnector->dc_sink = NULL;
aconnector->edid = NULL;
+ aconnector->dsc_aux = NULL;
+ port->passthrough_aux = NULL;

amdgpu_dm_set_mst_status(&aconnector->mst_status,
MST_REMOTE_EDID | MST_ALLOCATE_NEW_PAYLOAD | MST_CLEAR_ALLOCATED_PAYLOAD,
@@ -1233,14 +1237,6 @@ static bool is_dsc_need_re_compute(
if (!aconnector || !aconnector->dsc_aux)
continue;

- /*
- * check if cached virtual MST DSC caps are available and DSC is supported
- * as per specifications in their Virtual DPCD registers.
- */
- if (!(aconnector->dc_sink->dsc_caps.dsc_dec_caps.is_dsc_supported ||
- aconnector->dc_link->dpcd_caps.dsc_caps.dsc_basic_caps.fields.dsc_support.DSC_PASSTHROUGH_SUPPORT))
- continue;
-
stream_on_link[new_stream_on_link_num] = aconnector;
new_stream_on_link_num++;

--
2.43.0