drm/amd/display: Expand dc to use 16.16 bit backlight

[Why] We want to increase precision for backlight setting.
But DC interface takes 8 bit backlight level value only.

[How] DMCU already takes 16 bit backlight level.
Expand the DC interface to take 16.16 bit value.
Max 32 bit backlight value (0xFFFF) will represent
max backlight (100%)
Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -1580,8 +1580,14 @@ static int amdgpu_dm_backlight_update_status(struct backlight_device *bd)
 	 */
 	if (bd->props.brightness < 1)
 		return 1;
+
+	/* backlight_pwm_u16_16 parameter is in unsigned 32 bit, 16 bit integer
+	 * and 16 bit fractional, where 1.0 is max backlight value.
+	 * bd->props.brightness is 8 bit format and needs to be converted by
+	 * scaling via copy lower byte to upper byte of 16 bit value.
+	 */
 	if (dc_link_set_backlight_level(dm->backlight_link,
-			bd->props.brightness, 0, 0))
+			(bd->props.brightness * 0x101), 0, 0))
 		return 0;
 	else
 		return 1;

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

@@ -2141,14 +2141,16 @@ int dc_link_get_backlight_level(const struct dc_link *link)
 {
 	struct abm *abm = link->ctx->dc->res_pool->abm;
 
-	if (abm == NULL || abm->funcs->get_current_backlight_8_bit == NULL)
+	if (abm == NULL || abm->funcs->get_current_backlight == NULL)
 		return DC_ERROR_UNEXPECTED;
 
-	return (int) abm->funcs->get_current_backlight_8_bit(abm);
+	return (int) abm->funcs->get_current_backlight(abm);
 }
 
-bool dc_link_set_backlight_level(const struct dc_link *link, uint32_t level,
-		uint32_t frame_ramp, const struct dc_stream_state *stream)
+bool dc_link_set_backlight_level(const struct dc_link *link,
+		uint32_t backlight_pwm_u16_16,
+		uint32_t frame_ramp,
+		const struct dc_stream_state *stream)
 {
 	struct dc  *core_dc = link->ctx->dc;
 	struct abm *abm = core_dc->res_pool->abm;
@@ -2160,19 +2162,17 @@ bool dc_link_set_backlight_level(const struct dc_link *link, uint32_t level,
 
 	if ((dmcu == NULL) ||
 		(abm == NULL) ||
-		(abm->funcs->set_backlight_level == NULL))
+		(abm->funcs->set_backlight_level_pwm == NULL))
 		return false;
 
-	if (stream) {
-		if (stream->bl_pwm_level == EDP_BACKLIGHT_RAMP_DISABLE_LEVEL)
-			frame_ramp = 0;
-
-		((struct dc_stream_state *)stream)->bl_pwm_level = level;
-	}
+	if (stream)
+		((struct dc_stream_state *)stream)->bl_pwm_level =
+				backlight_pwm_u16_16;
 
 	use_smooth_brightness = dmcu->funcs->is_dmcu_initialized(dmcu);
 
-	DC_LOG_BACKLIGHT("New Backlight level: %d (0x%X)\n", level, level);
+	DC_LOG_BACKLIGHT("New Backlight level: %d (0x%X)\n",
+			backlight_pwm_u16_16, backlight_pwm_u16_16);
 
 	if (dc_is_embedded_signal(link->connector_signal)) {
 		if (stream != NULL) {
@@ -2189,9 +2189,9 @@ bool dc_link_set_backlight_level(const struct dc_link *link, uint32_t level,
 						1;
 			}
 		}
-		abm->funcs->set_backlight_level(
+		abm->funcs->set_backlight_level_pwm(
 				abm,
-				level,
+				backlight_pwm_u16_16,
 				frame_ramp,
 				controller_id,
 				use_smooth_brightness);
@@ -2205,7 +2205,7 @@ bool dc_link_set_abm_disable(const struct dc_link *link)
 	struct dc  *core_dc = link->ctx->dc;
 	struct abm *abm = core_dc->res_pool->abm;
 
-	if ((abm == NULL) || (abm->funcs->set_backlight_level == NULL))
+	if ((abm == NULL) || (abm->funcs->set_backlight_level_pwm == NULL))
 		return false;
 
 	abm->funcs->set_abm_immediate_disable(abm);
@@ -2594,6 +2594,10 @@ void core_link_enable_stream(
 		core_dc->hwss.unblank_stream(pipe_ctx,
 			&pipe_ctx->stream->sink->link->cur_link_settings);
 
+		dc_link_set_backlight_level(pipe_ctx->stream->sink->link,
+				pipe_ctx->stream->bl_pwm_level,
+				0,
+				pipe_ctx->stream);
 	}
 
 }

drivers/gpu/drm/amd/display/dc/dc_link.h

@@ -138,9 +138,14 @@ static inline struct dc_link *dc_get_link_at_index(struct dc *dc, uint32_t link_
 	return dc->links[link_index];
 }
 
-/* Set backlight level of an embedded panel (eDP, LVDS). */
-bool dc_link_set_backlight_level(const struct dc_link *dc_link, uint32_t level,
-		uint32_t frame_ramp, const struct dc_stream_state *stream);
+/* Set backlight level of an embedded panel (eDP, LVDS).
+ * backlight_pwm_u16_16 is unsigned 32 bit with 16 bit integer
+ * and 16 bit fractional, where 1.0 is max backlight value.
+ */
+bool dc_link_set_backlight_level(const struct dc_link *dc_link,
+		uint32_t backlight_pwm_u16_16,
+		uint32_t frame_ramp,
+		const struct dc_stream_state *stream);
 
 int dc_link_get_backlight_level(const struct dc_link *dc_link);
 

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

@@ -54,7 +54,7 @@
 #define MCP_DISABLE_ABM_IMMEDIATELY 255
 
 
-static unsigned int get_current_backlight_16_bit(struct dce_abm *abm_dce)
+static unsigned int calculate_16_bit_backlight_from_pwm(struct dce_abm *abm_dce)
 {
 	uint64_t current_backlight;
 	uint32_t round_result;
@@ -103,45 +103,21 @@ static unsigned int get_current_backlight_16_bit(struct dce_abm *abm_dce)
 	return (uint32_t)(current_backlight);
 }
 
-static void driver_set_backlight_level(struct dce_abm *abm_dce, uint32_t level)
+static void driver_set_backlight_level(struct dce_abm *abm_dce,
+		uint32_t backlight_pwm_u16_16)
 {
-	uint32_t backlight_24bit;
-	uint32_t backlight_17bit;
 	uint32_t backlight_16bit;
 	uint32_t masked_pwm_period;
-	uint8_t rounding_bit;
 	uint8_t bit_count;
 	uint64_t active_duty_cycle;
 	uint32_t pwm_period_bitcnt;
 
 	/*
-	 * 1. Convert 8-bit value to 17 bit U1.16 format
-	 * (1 integer, 16 fractional bits)
-	 */
-
-	/* 1.1 multiply 8 bit value by 0x10101 to get a 24 bit value,
-	 * effectively multiplying value by 256/255
-	 * eg. for a level of 0xEF, backlight_24bit = 0xEF * 0x10101 = 0xEFEFEF
-	 */
-	backlight_24bit = level * 0x10101;
-
-	/* 1.2 The upper 16 bits of the 24 bit value is the fraction, lower 8
-	 * used for rounding, take most significant bit of fraction for
-	 * rounding, e.g. for 0xEFEFEF, rounding bit is 1
-	 */
-	rounding_bit = (backlight_24bit >> 7) & 1;
-
-	/* 1.3 Add the upper 16 bits of the 24 bit value with the rounding bit
-	 * resulting in a 17 bit value e.g. 0xEFF0 = (0xEFEFEF >> 8) + 1
-	 */
-	backlight_17bit = (backlight_24bit >> 8) + rounding_bit;
-
-	/*
-	 * 2. Find  16 bit backlight active duty cycle, where 0 <= backlight
+	 * 1. Find  16 bit backlight active duty cycle, where 0 <= backlight
 	 * active duty cycle <= backlight period
 	 */
 
-	/* 2.1 Apply bitmask for backlight period value based on value of BITCNT
+	/* 1.1 Apply bitmask for backlight period value based on value of BITCNT
 	 */
 	REG_GET_2(BL_PWM_PERIOD_CNTL,
 			BL_PWM_PERIOD_BITCNT, &pwm_period_bitcnt,
@@ -155,13 +131,13 @@ static void driver_set_backlight_level(struct dce_abm *abm_dce, uint32_t level)
 	/* e.g. maskedPwmPeriod = 0x24 when bitCount is 6 */
 	masked_pwm_period = masked_pwm_period & ((1 << bit_count) - 1);
 
-	/* 2.2 Calculate integer active duty cycle required upper 16 bits
+	/* 1.2 Calculate integer active duty cycle required upper 16 bits
 	 * contain integer component, lower 16 bits contain fractional component
 	 * of active duty cycle e.g. 0x21BDC0 = 0xEFF0 * 0x24
 	 */
-	active_duty_cycle = backlight_17bit * masked_pwm_period;
+	active_duty_cycle = backlight_pwm_u16_16 * masked_pwm_period;
 
-	/* 2.3 Calculate 16 bit active duty cycle from integer and fractional
+	/* 1.3 Calculate 16 bit active duty cycle from integer and fractional
 	 * components shift by bitCount then mask 16 bits and add rounding bit
 	 * from MSB of fraction e.g. 0x86F7 = ((0x21BDC0 >> 6) & 0xFFF) + 0
 	 */
@@ -170,23 +146,23 @@ static void driver_set_backlight_level(struct dce_abm *abm_dce, uint32_t level)
 	backlight_16bit += (active_duty_cycle >> (bit_count - 1)) & 0x1;
 
 	/*
-	 * 3. Program register with updated value
+	 * 2. Program register with updated value
 	 */
 
-	/* 3.1 Lock group 2 backlight registers */
+	/* 2.1 Lock group 2 backlight registers */
 
 	REG_UPDATE_2(BL_PWM_GRP1_REG_LOCK,
 			BL_PWM_GRP1_IGNORE_MASTER_LOCK_EN, 1,
 			BL_PWM_GRP1_REG_LOCK, 1);
 
-	// 3.2 Write new active duty cycle
+	// 2.2 Write new active duty cycle
 	REG_UPDATE(BL_PWM_CNTL, BL_ACTIVE_INT_FRAC_CNT, backlight_16bit);
 
-	/* 3.3 Unlock group 2 backlight registers */
+	/* 2.3 Unlock group 2 backlight registers */
 	REG_UPDATE(BL_PWM_GRP1_REG_LOCK,
 			BL_PWM_GRP1_REG_LOCK, 0);
 
-	/* 5.4.4 Wait for pending bit to be cleared */
+	/* 3 Wait for pending bit to be cleared */
 	REG_WAIT(BL_PWM_GRP1_REG_LOCK,
 			BL_PWM_GRP1_REG_UPDATE_PENDING, 0,
 			1, 10000);
@@ -194,16 +170,21 @@ static void driver_set_backlight_level(struct dce_abm *abm_dce, uint32_t level)
 
 static void dmcu_set_backlight_level(
 	struct dce_abm *abm_dce,
-	uint32_t level,
+	uint32_t backlight_pwm_u16_16,
 	uint32_t frame_ramp,
 	uint32_t controller_id)
 {
-	unsigned int backlight_16_bit = (level * 0x10101) >> 8;
-	unsigned int backlight_17_bit = backlight_16_bit +
-				(((backlight_16_bit & 0x80) >> 7) & 1);
+	unsigned int backlight_8_bit = 0;
 	uint32_t rampingBoundary = 0xFFFF;
 	uint32_t s2;
 
+	if (backlight_pwm_u16_16 & 0x10000)
+		// Check for max backlight condition
+		backlight_8_bit = 0xFF;
+	else
+		// Take MSB of fractional part since backlight is not max
+		backlight_8_bit = (backlight_pwm_u16_16 >> 8) & 0xFF;
+
 	/* set ramping boundary */
 	REG_WRITE(MASTER_COMM_DATA_REG1, rampingBoundary);
 
@@ -220,7 +201,7 @@ static void dmcu_set_backlight_level(
 			0, 1, 80000);
 
 	/* setDMCUParam_BL */
-	REG_UPDATE(BL1_PWM_USER_LEVEL, BL1_PWM_USER_LEVEL, backlight_17_bit);
+	REG_UPDATE(BL1_PWM_USER_LEVEL, BL1_PWM_USER_LEVEL, backlight_pwm_u16_16);
 
 	/* write ramp */
 	if (controller_id == 0)
@@ -237,9 +218,9 @@ static void dmcu_set_backlight_level(
 	s2 = REG_READ(BIOS_SCRATCH_2);
 
 	s2 &= ~ATOM_S2_CURRENT_BL_LEVEL_MASK;
-	level &= (ATOM_S2_CURRENT_BL_LEVEL_MASK >>
+	backlight_8_bit &= (ATOM_S2_CURRENT_BL_LEVEL_MASK >>
 				ATOM_S2_CURRENT_BL_LEVEL_SHIFT);
-	s2 |= (level << ATOM_S2_CURRENT_BL_LEVEL_SHIFT);
+	s2 |= (backlight_8_bit << ATOM_S2_CURRENT_BL_LEVEL_SHIFT);
 
 	REG_WRITE(BIOS_SCRATCH_2, s2);
 }
@@ -247,7 +228,7 @@ static void dmcu_set_backlight_level(
 static void dce_abm_init(struct abm *abm)
 {
 	struct dce_abm *abm_dce = TO_DCE_ABM(abm);
-	unsigned int backlight = get_current_backlight_16_bit(abm_dce);
+	unsigned int backlight = calculate_16_bit_backlight_from_pwm(abm_dce);
 
 	REG_WRITE(DC_ABM1_HG_SAMPLE_RATE, 0x103);
 	REG_WRITE(DC_ABM1_HG_SAMPLE_RATE, 0x101);
@@ -284,12 +265,15 @@ static void dce_abm_init(struct abm *abm)
 			ABM1_BL_REG_READ_MISSED_FRAME_CLEAR, 1);
 }
 
-static unsigned int dce_abm_get_current_backlight_8_bit(struct abm *abm)
+static unsigned int dce_abm_get_current_backlight(struct abm *abm)
 {
 	struct dce_abm *abm_dce = TO_DCE_ABM(abm);
 	unsigned int backlight = REG_READ(BL1_PWM_CURRENT_ABM_LEVEL);
 
-	return (backlight >> 8);
+	/* return backlight in hardware format which is unsigned 17 bits, with
+	 * 1 bit integer and 16 bit fractional
+	 */
+	return backlight;
 }
 
 static bool dce_abm_set_level(struct abm *abm, uint32_t level)
@@ -396,9 +380,9 @@ static bool dce_abm_init_backlight(struct abm *abm)
 	return true;
 }
 
-static bool dce_abm_set_backlight_level(
+static bool dce_abm_set_backlight_level_pwm(
 		struct abm *abm,
-		unsigned int backlight_level,
+		unsigned int backlight_pwm_u16_16,
 		unsigned int frame_ramp,
 		unsigned int controller_id,
 		bool use_smooth_brightness)
@@ -406,16 +390,16 @@ static bool dce_abm_set_backlight_level(
 	struct dce_abm *abm_dce = TO_DCE_ABM(abm);
 
 	DC_LOG_BACKLIGHT("New Backlight level: %d (0x%X)\n",
-			backlight_level, backlight_level);
+			backlight_pwm_u16_16, backlight_pwm_u16_16);
 
 	/* If DMCU is in reset state, DMCU is uninitialized */
 	if (use_smooth_brightness)
 		dmcu_set_backlight_level(abm_dce,
-				backlight_level,
+				backlight_pwm_u16_16,
 				frame_ramp,
 				controller_id);
 	else
-		driver_set_backlight_level(abm_dce, backlight_level);
+		driver_set_backlight_level(abm_dce, backlight_pwm_u16_16);
 
 	return true;
 }
@@ -424,8 +408,8 @@ static const struct abm_funcs dce_funcs = {
 	.abm_init = dce_abm_init,
 	.set_abm_level = dce_abm_set_level,
 	.init_backlight = dce_abm_init_backlight,
-	.set_backlight_level = dce_abm_set_backlight_level,
-	.get_current_backlight_8_bit = dce_abm_get_current_backlight_8_bit,
+	.set_backlight_level_pwm = dce_abm_set_backlight_level_pwm,
+	.get_current_backlight = dce_abm_get_current_backlight,
 	.set_abm_immediate_disable = dce_abm_immediate_disable
 };
 

drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c

@@ -1085,7 +1085,6 @@ void dce110_unblank_stream(struct pipe_ctx *pipe_ctx,
 
 	if (link->local_sink && link->local_sink->sink_signal == SIGNAL_TYPE_EDP) {
 		link->dc->hwss.edp_backlight_control(link, true);
-		stream->bl_pwm_level = EDP_BACKLIGHT_RAMP_DISABLE_LEVEL;
 	}
 }
 void dce110_blank_stream(struct pipe_ctx *pipe_ctx)

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

@@ -47,12 +47,17 @@ struct abm_funcs {
 	bool (*set_abm_level)(struct abm *abm, unsigned int abm_level);
 	bool (*set_abm_immediate_disable)(struct abm *abm);
 	bool (*init_backlight)(struct abm *abm);
-	bool (*set_backlight_level)(struct abm *abm,
-			unsigned int backlight_level,
+
+	/* backlight_pwm_u16_16 is unsigned 32 bit,
+	 * 16 bit integer + 16 fractional, where 1.0 is max backlight value.
+	 */
+	bool (*set_backlight_level_pwm)(struct abm *abm,
+			unsigned int backlight_pwm_u16_16,
 			unsigned int frame_ramp,
 			unsigned int controller_id,
 			bool use_smooth_brightness);
-	unsigned int (*get_current_backlight_8_bit)(struct abm *abm);
+
+	unsigned int (*get_current_backlight)(struct abm *abm);
 };
 
 #endif

drivers/gpu/drm/amd/display/dc/inc/hw_sequencer.h

@@ -32,8 +32,6 @@
 #include "inc/hw/link_encoder.h"
 #include "core_status.h"
 
-#define EDP_BACKLIGHT_RAMP_DISABLE_LEVEL 0xFFFFFFFF
-
 enum pipe_gating_control {
 	PIPE_GATING_CONTROL_DISABLE = 0,
 	PIPE_GATING_CONTROL_ENABLE,