drm/amd/display: fix issue with DC brightness low with VB

[Why]
The problem is that we accidentally stopped loading some of the IRAM bytes
used for the backlight ramping mechanism. This happened when we
started reserving some region of IRAM as DMCU FW write only.

[How]
This change will define a start+end region for the IRAM read only region.
So the parameters needed for the backlight operation will be loaded
since it will be defined outside of the read only region.

Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/modules/power/power_helpers.c

@@ -67,9 +67,14 @@ static const unsigned char abm_config[abm_defines_max_config][abm_defines_max_le
 #define NUM_AGGR_LEVEL    4
 #define NUM_POWER_FN_SEGS 8
 #define NUM_BL_CURVE_SEGS 16
-#define IRAM_RESERVE_AREA_START 0xF0  // reserve 0xF0~0xFF are write by DMCU only
 #define IRAM_SIZE 256
 
+#define IRAM_RESERVE_AREA_START_V2 0xF0  // reserve 0xF0~0xF6 are write by DMCU only
+#define IRAM_RESERVE_AREA_END_V2 0xF6  // reserve 0xF0~0xF6 are write by DMCU only
+
+#define IRAM_RESERVE_AREA_START_V2_2 0xF0  // reserve 0xF0~0xFF are write by DMCU only
+#define IRAM_RESERVE_AREA_END_V2_2 0xFF  // reserve 0xF0~0xFF are write by DMCU only
+
 #pragma pack(push, 1)
 /* NOTE: iRAM is 256B in size */
 struct iram_table_v_2 {
@@ -148,8 +153,10 @@ struct iram_table_v_2_2 {
 	uint16_t dmcu_version;										/* 0xf4       */
 	uint8_t dmcu_state;											/* 0xf6       */
 
-	uint16_t blRampReduction;									/* 0xf7       */
-	uint16_t blRampStart;										/* 0xf9       */
+	uint8_t dummy1;												/* 0xf7       */
+	uint8_t dummy2;												/* 0xf8       */
+	uint8_t dummy3;												/* 0xf9       */
+	uint8_t dummy4;												/* 0xfa       */
 	uint8_t dummy5;												/* 0xfb       */
 	uint8_t dummy6;												/* 0xfc       */
 	uint8_t dummy7;												/* 0xfd       */
@@ -420,11 +427,6 @@ void fill_iram_v_2_2(struct iram_table_v_2_2 *ram_table, struct dmcu_iram_parame
 	ram_table->deviation_gain[2] = 0xb3;
 	ram_table->deviation_gain[3] = 0xb3;
 
-	ram_table->blRampReduction =
-		cpu_to_be16(params.backlight_ramping_reduction);
-	ram_table->blRampStart =
-		cpu_to_be16(params.backlight_ramping_start);
-
 	ram_table->min_reduction[0][0] = min_reduction_table_v_2_2[abm_config[set][0]];
 	ram_table->min_reduction[1][0] = min_reduction_table_v_2_2[abm_config[set][0]];
 	ram_table->min_reduction[2][0] = min_reduction_table_v_2_2[abm_config[set][0]];
@@ -561,6 +563,7 @@ bool dmcu_load_iram(struct dmcu *dmcu,
 	struct dmcu_iram_parameters params)
 {
 	unsigned char ram_table[IRAM_SIZE];
+	bool result = false;
 
 	if (dmcu == NULL)
 		return false;
@@ -572,10 +575,21 @@ bool dmcu_load_iram(struct dmcu *dmcu,
 
 	if (dmcu->dmcu_version.abm_version == 0x22) {
 		fill_iram_v_2_2((struct iram_table_v_2_2 *)ram_table, params);
+
+		result = dmcu->funcs->load_iram(
+				dmcu, 0, (char *)(&ram_table), IRAM_RESERVE_AREA_START_V2_2);
 	} else {
 		fill_iram_v_2((struct iram_table_v_2 *)ram_table, params);
+
+		result = dmcu->funcs->load_iram(
+				dmcu, 0, (char *)(&ram_table), IRAM_RESERVE_AREA_START_V2);
+
+		if (result)
+			result = dmcu->funcs->load_iram(
+					dmcu, IRAM_RESERVE_AREA_END_V2 + 1,
+					(char *)(&ram_table) + IRAM_RESERVE_AREA_END_V2 + 1,
+					sizeof(ram_table) - IRAM_RESERVE_AREA_END_V2 - 1);
 	}
 
-	return dmcu->funcs->load_iram(
-			dmcu, 0, (char *)(&ram_table), IRAM_RESERVE_AREA_START);
+	return result;
 }