drm/amd/display: Add SetBacklight call to abm on dmcub

[Why]
Set backlight calls to firmware are are being prevented by dmcu == null
check. Dmcu is expected to be null in this case.

[How]
Only prevent call if dmcu and abm are null.  Also rename variable
'use_smooth_brightness' to 'fw_set_brightness' as it's more appropriate.
Signed-off-by: Wyatt Wood <wyatt.wood@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link.c

@@ -2455,16 +2455,16 @@ bool dc_link_set_backlight_level(const struct dc_link *link,
 	struct abm *abm = dc->res_pool->abm;
 	struct dmcu *dmcu = dc->res_pool->dmcu;
 	unsigned int controller_id = 0;
-	bool use_smooth_brightness = true;
+	bool fw_set_brightness = true;
 	int i;
 	DC_LOGGER_INIT(link->ctx->logger);
 
-	if ((dmcu == NULL) ||
-		(abm == NULL) ||
+	if ((dmcu == NULL && abm == NULL) ||
 		(abm->funcs->set_backlight_level_pwm == NULL))
 		return false;
 
-	use_smooth_brightness = dmcu->funcs->is_dmcu_initialized(dmcu);
+	if (dmcu)
+		fw_set_brightness = dmcu->funcs->is_dmcu_initialized(dmcu);
 
 	DC_LOG_BACKLIGHT("New Backlight level: %d (0x%X)\n",
 			backlight_pwm_u16_16, backlight_pwm_u16_16);
@@ -2496,7 +2496,7 @@ bool dc_link_set_backlight_level(const struct dc_link *link,
 				backlight_pwm_u16_16,
 				frame_ramp,
 				controller_id,
-				use_smooth_brightness);
+				fw_set_brightness);
 	}
 
 	return true;

drivers/gpu/drm/amd/display/dc/dce/dce_abm.c

@@ -420,7 +420,7 @@ static bool dce_abm_set_backlight_level_pwm(
 		unsigned int backlight_pwm_u16_16,
 		unsigned int frame_ramp,
 		unsigned int controller_id,
-		bool use_smooth_brightness)
+		bool fw_set_brightness)
 {
 	struct dce_abm *abm_dce = TO_DCE_ABM(abm);
 
@@ -428,7 +428,7 @@ static bool dce_abm_set_backlight_level_pwm(
 			backlight_pwm_u16_16, backlight_pwm_u16_16);
 
 	/* If DMCU is in reset state, DMCU is uninitialized */
-	if (use_smooth_brightness)
+	if (fw_set_brightness)
 		dmcu_set_backlight_level(abm_dce,
 				backlight_pwm_u16_16,
 				frame_ramp,

drivers/gpu/drm/amd/display/dc/dce/dmub_abm.c

@@ -338,7 +338,7 @@ static bool dmub_abm_set_backlight_level_pwm(
 		unsigned int backlight_pwm_u16_16,
 		unsigned int frame_ramp,
 		unsigned int otg_inst,
-		bool use_smooth_brightness)
+		bool fw_set_brightness)
 {
 	struct dce_abm *dce_abm = TO_DMUB_ABM(abm);
 

drivers/gpu/drm/amd/display/dc/inc/hw/abm.h

@@ -56,7 +56,7 @@ struct abm_funcs {
 			unsigned int backlight_pwm_u16_16,
 			unsigned int frame_ramp,
 			unsigned int controller_id,
-			bool use_smooth_brightness);
+			bool fw_set_brightness);
 
 	unsigned int (*get_current_backlight)(struct abm *abm);
 	unsigned int (*get_target_backlight)(struct abm *abm);