[PATCH v2] drm/amd/display: Add NULL check for clk_mgr and clk_mgr->funcs in dcn401_init_hw

[Srinivasan Shanmugam <srinivasan.shanmugam@xxxxxxx>]

This commit addresses a potential null pointer dereference issue in the
`dcn401_init_hw` function. The issue could occur when `dc->clk_mgr` or
`dc->clk_mgr->funcs` is null.

The fix adds a check to ensure `dc->clk_mgr` and `dc->clk_mgr->funcs` is
not null before accessing its functions. This prevents a potential null
pointer dereference.

Reported by smatch:
drivers/gpu/drm/amd/amdgpu/../display/dc/hwss/dcn401/dcn401_hwseq.c:416 dcn401_init_hw() error: we previously assumed 'dc->clk_mgr' could be null (see line 225)

Cc: Tom Chung <chiahsuan.chung@xxxxxxx>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@xxxxxxx>
Cc: Roman Li <roman.li@xxxxxxx>
Cc: Alex Hung <alex.hung@xxxxxxx>
Cc: Aurabindo Pillai <aurabindo.pillai@xxxxxxx>
Cc: Harry Wentland <harry.wentland@xxxxxxx>
Cc: Hamza Mahfooz <hamza.mahfooz@xxxxxxx>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@xxxxxxx>
---
v2: Along with "dc->clk_mgr" add check for even dc->clk_mgr->funcs" (Tom)

 drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c
index 87c5ef579ecb..0fa610590245 100644
--- a/drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c
@@ -222,7 +222,7 @@ void dcn401_init_hw(struct dc *dc)
 	uint32_t backlight = MAX_BACKLIGHT_LEVEL;
 	uint32_t user_level = MAX_BACKLIGHT_LEVEL;
 
-	if (dc->clk_mgr && dc->clk_mgr->funcs->init_clocks) {
+	if (dc->clk_mgr && dc->clk_mgr->funcs && dc->clk_mgr->funcs->init_clocks) {
 		dc->clk_mgr->funcs->init_clocks(dc->clk_mgr);
 
 		// mark dcmode limits present if any clock has distinct AC and DC values from SMU
@@ -413,7 +413,7 @@ void dcn401_init_hw(struct dc *dc)
 	if (!dcb->funcs->is_accelerated_mode(dcb) && dc->res_pool->hubbub->funcs->init_watermarks)
 		dc->res_pool->hubbub->funcs->init_watermarks(dc->res_pool->hubbub);
 
-	if (dc->clk_mgr->funcs->notify_wm_ranges)
+	if (dc->clk_mgr && dc->clk_mgr->funcs && dc->clk_mgr->funcs->notify_wm_ranges)
 		dc->clk_mgr->funcs->notify_wm_ranges(dc->clk_mgr);
 
 	if (dc->res_pool->hubbub->funcs->force_pstate_change_control)
@@ -435,7 +435,9 @@ void dcn401_init_hw(struct dc *dc)
 		dc->debug.fams2_config.bits.enable &= dc->ctx->dmub_srv->dmub->feature_caps.fw_assisted_mclk_switch_ver == 2;
 		if (!dc->debug.fams2_config.bits.enable && dc->res_pool->funcs->update_bw_bounding_box) {
 			/* update bounding box if FAMS2 disabled */
-			dc->res_pool->funcs->update_bw_bounding_box(dc, dc->clk_mgr->bw_params);
+			if (dc->clk_mgr)
+				dc->res_pool->funcs->update_bw_bounding_box(dc,
+									    dc->clk_mgr->bw_params);
 		}
 	}
 }
-- 
2.34.1