[PATCH] drm/amd/display: Fix NULL pointer dereference for program_lut_mode in dcn401_populate_mcm_luts

[Srinivasan Shanmugam]

This commit introduces a NULL pointer check for
mpc->funcs->program_lut_mode in the dcn401_populate_mcm_luts function.
The previous implementation directly called program_lut_mode without
validating its existence, which could lead to a NULL pointer
dereference.

With this change, the function is now only invoked if
mpc->funcs->program_lut_mode is not NULL

Fixes the below:

drivers/gpu/drm/amd/amdgpu/../display/dc/hwss/dcn401/dcn401_hwseq.c:720 dcn401_populate_mcm_luts()
error: we previously assumed 'mpc->funcs->program_lut_mode' could be null (see line 701)

drivers/gpu/drm/amd/amdgpu/../display/dc/hwss/dcn401/dcn401_hwseq.c
    642 void dcn401_populate_mcm_luts(struct dc *dc,
    643                 struct pipe_ctx *pipe_ctx,
    644                 struct dc_cm2_func_luts mcm_luts,
    645                 bool lut_bank_a)
    646 {
	...
    716                 }
    717                 if (m_lut_params.pwl) {
    718                         if (mpc->funcs->mcm.populate_lut)
    719                                 mpc->funcs->mcm.populate_lut(mpc, m_lut_params, lut_bank_a, mpcc_id);
--> 720                         mpc->funcs->program_lut_mode(mpc, MCM_LUT_SHAPER, MCM_LUT_ENABLE, lut_bank_a, mpcc_id);

Cc: Yihan Zhu <yihanzhu at amd.com>
Cc: Harry Wentland <harry.wentland at amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
Cc: Tom Chung <chiahsuan.chung at amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
Cc: Roman Li <roman.li at amd.com>
Cc: Alex Hung <alex.hung at amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai at amd.com>
Reported-by: Dan Carpenter <dan.carpenter at linaro.org>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
---
 drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

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 8611eb9607df..ae7194da5987 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
@@ -717,7 +717,8 @@ void dcn401_populate_mcm_luts(struct dc *dc,
 		if (m_lut_params.pwl) {
 			if (mpc->funcs->mcm.populate_lut)
 				mpc->funcs->mcm.populate_lut(mpc, m_lut_params, lut_bank_a, mpcc_id);
-			mpc->funcs->program_lut_mode(mpc, MCM_LUT_SHAPER, MCM_LUT_ENABLE, lut_bank_a, mpcc_id);
+			if (mpc->funcs->program_lut_mode)
+				mpc->funcs->program_lut_mode(mpc, MCM_LUT_SHAPER, MCM_LUT_ENABLE, lut_bank_a, mpcc_id);
 		}
 	}
 
-- 
2.34.1