[PATCH v5.15] drm/amd/display: Check dce_hwseq before dereferencing it

[Rahul Sharma <black.hawk@163.com>]

From: Alex Hung <alex.hung@amd.com>

[ Upstream b669507b637eb6b1aaecf347f193efccc65d756e commit ]

[WHAT]

hws was checked for null earlier in dce110_blank_stream, indicating hws
can be null, and should be checked whenever it is used.

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 79db43611ff61280b6de58ce1305e0b2ecf675ad)
Cc: stable@vger.kernel.org
[ The context change is due to the commit 8e7b3f5435b3
("drm/amd/display: Add control flag to dc_stream_state to skip eDP BL off/link off")
and the commit a8728dbb4ba2 ("drm/amd/display: Refactor edp power control")
and the proper adoption is done. ]
Signed-off-by: Rahul Sharma <black.hawk@163.com>
---
 drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c b/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c
index 87825818d43e..2da3fd6522bb 100644
--- a/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c
+++ b/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c
@@ -1208,7 +1208,8 @@ void dce110_blank_stream(struct pipe_ctx *pipe_ctx)
 	struct dce_hwseq *hws = link->dc->hwseq;
 
 	if (link->local_sink && link->local_sink->sink_signal == SIGNAL_TYPE_EDP) {
-		hws->funcs.edp_backlight_control(link, false);
+		if (hws)
+			hws->funcs.edp_backlight_control(link, false);
 		link->dc->hwss.set_abm_immediate_disable(pipe_ctx);
 	}
 
-- 
2.34.1