drm/amd/display: Fix 'panel_cntl' could be null in 'dcn21_set_backlight_level()'

[ Upstream commit e96fddb32931d007db12b1fce9b5e8e4c080401b ]

'panel_cntl' structure used to control the display panel could be null,
dereferencing it could lead to a null pointer access.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../display/dc/hwss/dcn21/dcn21_hwseq.c:269 dcn21_set_backlight_level() error: we previously assumed 'panel_cntl' could be null (see line 250)

Fixes: 474ac4a875ca ("drm/amd/display: Implement some asic specific abm call backs.")
Cc: Yongqiang Sun <yongqiang.sun@amd.com>
Cc: Anthony Koo <Anthony.Koo@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_hwseq.c b/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_hwseq.c
index f99b1bc49694fb59c048776f55571863ac790cd6..7238930e6383f53f5164525b6c0eaa320bf89bd1 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_hwseq.c
@@ -237,34 +237,35 @@ bool dcn21_set_backlight_level(struct pipe_ctx *pipe_ctx,
 {
        struct dc_context *dc = pipe_ctx->stream->ctx;
        struct abm *abm = pipe_ctx->stream_res.abm;
+       struct timing_generator *tg = pipe_ctx->stream_res.tg;
        struct panel_cntl *panel_cntl = pipe_ctx->stream->link->panel_cntl;
+       uint32_t otg_inst;
+
+       if (!abm && !tg && !panel_cntl)
+               return false;
+
+       otg_inst = tg->inst;
 
        if (dc->dc->res_pool->dmcu) {
                dce110_set_backlight_level(pipe_ctx, backlight_pwm_u16_16, frame_ramp);
                return true;
        }
 
-       if (abm != NULL) {
-               uint32_t otg_inst = pipe_ctx->stream_res.tg->inst;
-
-               if (abm && panel_cntl) {
-                       if (abm->funcs && abm->funcs->set_pipe_ex) {
-                               abm->funcs->set_pipe_ex(abm,
-                                               otg_inst,
-                                               SET_ABM_PIPE_NORMAL,
-                                               panel_cntl->inst,
-                                               panel_cntl->pwrseq_inst);
-                       } else {
-                                       dmub_abm_set_pipe(abm,
-                                                       otg_inst,
-                                                       SET_ABM_PIPE_NORMAL,
-                                                       panel_cntl->inst,
-                                                       panel_cntl->pwrseq_inst);
-                       }
-               }
+       if (abm->funcs && abm->funcs->set_pipe_ex) {
+               abm->funcs->set_pipe_ex(abm,
+                                       otg_inst,
+                                       SET_ABM_PIPE_NORMAL,
+                                       panel_cntl->inst,
+                                       panel_cntl->pwrseq_inst);
+       } else {
+               dmub_abm_set_pipe(abm,
+                                 otg_inst,
+                                 SET_ABM_PIPE_NORMAL,
+                                 panel_cntl->inst,
+                                 panel_cntl->pwrseq_inst);
        }
 
-       if (abm && abm->funcs && abm->funcs->set_backlight_level_pwm)
+       if (abm->funcs && abm->funcs->set_backlight_level_pwm)
                abm->funcs->set_backlight_level_pwm(abm, backlight_pwm_u16_16,
                        frame_ramp, 0, panel_cntl->inst);
        else