linux-kernel - [PATCH AUTOSEL 6.10 19/34] drm/amd/display: Don't refer to dc_sink in is_dsc_need_re

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Message-ID: <20240728154230.2046786-19-sashal@kernel.org>
Date: Sun, 28 Jul 2024 11:40:43 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Wayne Lin <wayne.lin@....com>,
	Jerry Zuo <jerry.zuo@....com>,
	Zaeem Mohamed <zaeem.mohamed@....com>,
	Daniel Wheeler <daniel.wheeler@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Sasha Levin <sashal@...nel.org>,
	harry.wentland@....com,
	sunpeng.li@....com,
	Rodrigo.Siqueira@....com,
	christian.koenig@....com,
	Xinhui.Pan@....com,
	airlied@...il.com,
	daniel@...ll.ch,
	alex.hung@....com,
	roman.li@....com,
	hersenxs.wu@....com,
	mario.limonciello@....com,
	agustin.gutierrez@....com,
	hamza.mahfooz@....com,
	amd-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.10 19/34] drm/amd/display: Don't refer to dc_sink in is_dsc_need_re_compute

From: Wayne Lin <wayne.lin@....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@....com>
Acked-by: Zaeem Mohamed <zaeem.mohamed@....com>
Signed-off-by: Wayne Lin <wayne.lin@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.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