drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c - linux - Git at Google

 /*
  * Copyright 2012-15 Advanced Micro Devices, Inc.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
  * to deal in the Software without restriction, including without limitation
  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  * and/or sell copies of the Software, and to permit persons to whom the
  * Software is furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  * OTHER DEALINGS IN THE SOFTWARE.
  *
  * Authors: AMD
  *
  */

 #include "reg_helper.h"
 #include "core_types.h"
 #include "dc_dmub_srv.h"
 #include "panel_cntl.h"
 #include "dce_panel_cntl.h"
 #include "atom.h"

 #define TO_DCE_PANEL_CNTL(panel_cntl)\
 	container_of(panel_cntl, struct dce_panel_cntl, base)

 #define CTX \
 	dce_panel_cntl->base.ctx

 #define DC_LOGGER \
 	dce_panel_cntl->base.ctx->logger

 #define REG(reg)\
 	dce_panel_cntl->regs->reg

 #undef FN
 #define FN(reg_name, field_name) \
 	dce_panel_cntl->shift->field_name, dce_panel_cntl->mask->field_name

 static unsigned int dce_get_16_bit_backlight_from_pwm(struct panel_cntl *panel_cntl)
 {
 	uint64_t current_backlight;
 	uint32_t round_result;
 	uint32_t pwm_period_cntl, bl_period, bl_int_count;
 	uint32_t bl_pwm_cntl, bl_pwm, fractional_duty_cycle_en;
 	uint32_t bl_period_mask, bl_pwm_mask;
 	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);

 	pwm_period_cntl = REG_READ(BL_PWM_PERIOD_CNTL);
 	REG_GET(BL_PWM_PERIOD_CNTL, BL_PWM_PERIOD, &bl_period);
 	REG_GET(BL_PWM_PERIOD_CNTL, BL_PWM_PERIOD_BITCNT, &bl_int_count);

 	bl_pwm_cntl = REG_READ(BL_PWM_CNTL);
 	REG_GET(BL_PWM_CNTL, BL_ACTIVE_INT_FRAC_CNT, (uint32_t *)(&bl_pwm));
 	REG_GET(BL_PWM_CNTL, BL_PWM_FRACTIONAL_EN, &fractional_duty_cycle_en);

 	if (bl_int_count == 0)
 		bl_int_count = 16;

 	bl_period_mask = (1 << bl_int_count) - 1;
 	bl_period &= bl_period_mask;

 	bl_pwm_mask = bl_period_mask << (16 - bl_int_count);

 	if (fractional_duty_cycle_en == 0)
 		bl_pwm &= bl_pwm_mask;
 	else
 		bl_pwm &= 0xFFFF;

 	current_backlight = (uint64_t)bl_pwm << (1 + bl_int_count);

 	if (bl_period == 0)
 		bl_period = 0xFFFF;

 	current_backlight = div_u64(current_backlight, bl_period);
 	current_backlight = (current_backlight + 1) >> 1;

 	current_backlight = (uint64_t)(current_backlight) * bl_period;

 	round_result = (uint32_t)(current_backlight & 0xFFFFFFFF);

 	round_result = (round_result >> (bl_int_count-1)) & 1;

 	current_backlight >>= bl_int_count;
 	current_backlight += round_result;

 	return (uint32_t)(current_backlight);
 }

 static uint32_t dce_panel_cntl_hw_init(struct panel_cntl *panel_cntl)
 {
 	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);
 	uint32_t value;
 	uint32_t current_backlight;

 	/* It must not be 0, so we have to restore them
 	 * Bios bug w/a - period resets to zero,
 	 * restoring to cache values which is always correct
 	 */
 	REG_GET(BL_PWM_CNTL, BL_ACTIVE_INT_FRAC_CNT, &value);

 	if (value == 0 || value == 1) {
 		if (panel_cntl->stored_backlight_registers.BL_PWM_CNTL != 0) {
 			REG_WRITE(BL_PWM_CNTL,
 					panel_cntl->stored_backlight_registers.BL_PWM_CNTL);
 			REG_WRITE(BL_PWM_CNTL2,
 					panel_cntl->stored_backlight_registers.BL_PWM_CNTL2);
 			REG_WRITE(BL_PWM_PERIOD_CNTL,
 					panel_cntl->stored_backlight_registers.BL_PWM_PERIOD_CNTL);
 			REG_UPDATE(PWRSEQ_REF_DIV,
 				BL_PWM_REF_DIV,
 				panel_cntl->stored_backlight_registers.LVTMA_PWRSEQ_REF_DIV_BL_PWM_REF_DIV);
 		} else {
 			/* TODO: Note: This should not really happen since VBIOS
 			 * should have initialized PWM registers on boot.
 			 */
 			REG_WRITE(BL_PWM_CNTL, 0xC000FA00);
 			REG_WRITE(BL_PWM_PERIOD_CNTL, 0x000C0FA0);
 		}
 	} else {
 		panel_cntl->stored_backlight_registers.BL_PWM_CNTL =
 				REG_READ(BL_PWM_CNTL);
 		panel_cntl->stored_backlight_registers.BL_PWM_CNTL2 =
 				REG_READ(BL_PWM_CNTL2);
 		panel_cntl->stored_backlight_registers.BL_PWM_PERIOD_CNTL =
 				REG_READ(BL_PWM_PERIOD_CNTL);

 		REG_GET(PWRSEQ_REF_DIV, BL_PWM_REF_DIV,
 				&panel_cntl->stored_backlight_registers.LVTMA_PWRSEQ_REF_DIV_BL_PWM_REF_DIV);
 	}

 	// Have driver take backlight control
 	// TakeBacklightControl(true)
 	value = REG_READ(BIOS_SCRATCH_2);
 	value |= ATOM_S2_VRI_BRIGHT_ENABLE;
 	REG_WRITE(BIOS_SCRATCH_2, value);

 	// Enable the backlight output
 	REG_UPDATE(BL_PWM_CNTL, BL_PWM_EN, 1);

 	// Unlock group 2 backlight registers
 	REG_UPDATE(BL_PWM_GRP1_REG_LOCK,
 			BL_PWM_GRP1_REG_LOCK, 0);

 	current_backlight = dce_get_16_bit_backlight_from_pwm(panel_cntl);

 	return current_backlight;
 }

 static bool dce_is_panel_backlight_on(struct panel_cntl *panel_cntl)
 {
 	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);
 	uint32_t blon, blon_ovrd, pwrseq_target_state;

 	REG_GET_2(PWRSEQ_CNTL, LVTMA_BLON, &blon, LVTMA_BLON_OVRD, &blon_ovrd);
 	REG_GET(PWRSEQ_CNTL, LVTMA_PWRSEQ_TARGET_STATE, &pwrseq_target_state);

 	if (blon_ovrd)
 		return blon;
 	else
 		return pwrseq_target_state;
 }

 static bool dce_is_panel_powered_on(struct panel_cntl *panel_cntl)
 {
 	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);
 	uint32_t pwr_seq_state, dig_on, dig_on_ovrd;

 	REG_GET(PWRSEQ_STATE, LVTMA_PWRSEQ_TARGET_STATE_R, &pwr_seq_state);

 	REG_GET_2(PWRSEQ_CNTL, LVTMA_DIGON, &dig_on, LVTMA_DIGON_OVRD, &dig_on_ovrd);

 	return (pwr_seq_state == 1) || (dig_on == 1 && dig_on_ovrd == 1);
 }

 static void dce_store_backlight_level(struct panel_cntl *panel_cntl)
 {
 	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);

 	panel_cntl->stored_backlight_registers.BL_PWM_CNTL =
 		REG_READ(BL_PWM_CNTL);
 	panel_cntl->stored_backlight_registers.BL_PWM_CNTL2 =
 		REG_READ(BL_PWM_CNTL2);
 	panel_cntl->stored_backlight_registers.BL_PWM_PERIOD_CNTL =
 		REG_READ(BL_PWM_PERIOD_CNTL);

 	REG_GET(PWRSEQ_REF_DIV, BL_PWM_REF_DIV,
 		&panel_cntl->stored_backlight_registers.LVTMA_PWRSEQ_REF_DIV_BL_PWM_REF_DIV);
 }

 static void dce_driver_set_backlight(struct panel_cntl *panel_cntl,
 		uint32_t backlight_pwm_u16_16)
 {
 	uint32_t backlight_16bit;
 	uint32_t masked_pwm_period;
 	uint8_t bit_count;
 	uint64_t active_duty_cycle;
 	uint32_t pwm_period_bitcnt;
 	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);

 	/*
 	 * 1. Find  16 bit backlight active duty cycle, where 0 <= backlight
 	 * active duty cycle <= backlight period
 	 */

 	/* 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,
 			BL_PWM_PERIOD, &masked_pwm_period);

 	if (pwm_period_bitcnt == 0)
 		bit_count = 16;
 	else
 		bit_count = pwm_period_bitcnt;

 	/* e.g. maskedPwmPeriod = 0x24 when bitCount is 6 */
 	masked_pwm_period = masked_pwm_period & ((1 << bit_count) - 1);

 	/* 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_pwm_u16_16 * masked_pwm_period;

 	/* 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
 	 */
 	backlight_16bit = active_duty_cycle >> bit_count;
 	backlight_16bit &= 0xFFFF;
 	backlight_16bit += (active_duty_cycle >> (bit_count - 1)) & 0x1;

 	/*
 	 * 2. Program register with updated value
 	 */

 	/* 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);

 	// 2.2 Write new active duty cycle
 	REG_UPDATE(BL_PWM_CNTL, BL_ACTIVE_INT_FRAC_CNT, backlight_16bit);

 	/* 2.3 Unlock group 2 backlight registers */
 	REG_UPDATE(BL_PWM_GRP1_REG_LOCK,
 			BL_PWM_GRP1_REG_LOCK, 0);

 	/* 3 Wait for pending bit to be cleared */
 	REG_WAIT(BL_PWM_GRP1_REG_LOCK,
 			BL_PWM_GRP1_REG_UPDATE_PENDING, 0,
 			1, 10000);
 }

 static void dce_panel_cntl_destroy(struct panel_cntl **panel_cntl)
 {
 	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(*panel_cntl);

 	kfree(dce_panel_cntl);
 	*panel_cntl = NULL;
 }

 static const struct panel_cntl_funcs dce_link_panel_cntl_funcs = {
 	.destroy = dce_panel_cntl_destroy,
 	.hw_init = dce_panel_cntl_hw_init,
 	.is_panel_backlight_on = dce_is_panel_backlight_on,
 	.is_panel_powered_on = dce_is_panel_powered_on,
 	.store_backlight_level = dce_store_backlight_level,
 	.driver_set_backlight = dce_driver_set_backlight,
 	.get_current_backlight = dce_get_16_bit_backlight_from_pwm,
 };

 void dce_panel_cntl_construct(
 	struct dce_panel_cntl *dce_panel_cntl,
 	const struct panel_cntl_init_data *init_data,
 	const struct dce_panel_cntl_registers *regs,
 	const struct dce_panel_cntl_shift *shift,
 	const struct dce_panel_cntl_mask *mask)
 {
 	struct panel_cntl *base = &dce_panel_cntl->base;

 	base->stored_backlight_registers.BL_PWM_CNTL = 0;
 	base->stored_backlight_registers.BL_PWM_CNTL2 = 0;
 	base->stored_backlight_registers.BL_PWM_PERIOD_CNTL = 0;
 	base->stored_backlight_registers.LVTMA_PWRSEQ_REF_DIV_BL_PWM_REF_DIV = 0;

 	dce_panel_cntl->regs = regs;
 	dce_panel_cntl->shift = shift;
 	dce_panel_cntl->mask = mask;

 	dce_panel_cntl->base.funcs = &dce_link_panel_cntl_funcs;
 	dce_panel_cntl->base.ctx = init_data->ctx;
 	dce_panel_cntl->base.inst = init_data->inst;
 }
	/*
	* Copyright 2012-15 Advanced Micro Devices, Inc.
	*
	* Permission is hereby granted, free of charge, to any person obtaining a
	* copy of this software and associated documentation files (the "Software"),
	* to deal in the Software without restriction, including without limitation
	* the rights to use, copy, modify, merge, publish, distribute, sublicense,
	* and/or sell copies of the Software, and to permit persons to whom the
	* Software is furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
	* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
	* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
	* OTHER DEALINGS IN THE SOFTWARE.
	*
	* Authors: AMD
	*
	*/

	#include "reg_helper.h"
	#include "core_types.h"
	#include "dc_dmub_srv.h"
	#include "panel_cntl.h"
	#include "dce_panel_cntl.h"
	#include "atom.h"

	#define TO_DCE_PANEL_CNTL(panel_cntl)\
	container_of(panel_cntl, struct dce_panel_cntl, base)

	#define CTX \
	dce_panel_cntl->base.ctx

	#define DC_LOGGER \
	dce_panel_cntl->base.ctx->logger

	#define REG(reg)\
	dce_panel_cntl->regs->reg

	#undef FN
	#define FN(reg_name, field_name) \
	dce_panel_cntl->shift->field_name, dce_panel_cntl->mask->field_name

	static unsigned int dce_get_16_bit_backlight_from_pwm(struct panel_cntl *panel_cntl)
	{
	uint64_t current_backlight;
	uint32_t round_result;
	uint32_t pwm_period_cntl, bl_period, bl_int_count;
	uint32_t bl_pwm_cntl, bl_pwm, fractional_duty_cycle_en;
	uint32_t bl_period_mask, bl_pwm_mask;
	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);

	pwm_period_cntl = REG_READ(BL_PWM_PERIOD_CNTL);
	REG_GET(BL_PWM_PERIOD_CNTL, BL_PWM_PERIOD, &bl_period);
	REG_GET(BL_PWM_PERIOD_CNTL, BL_PWM_PERIOD_BITCNT, &bl_int_count);

	bl_pwm_cntl = REG_READ(BL_PWM_CNTL);
	REG_GET(BL_PWM_CNTL, BL_ACTIVE_INT_FRAC_CNT, (uint32_t *)(&bl_pwm));
	REG_GET(BL_PWM_CNTL, BL_PWM_FRACTIONAL_EN, &fractional_duty_cycle_en);

	if (bl_int_count == 0)
	bl_int_count = 16;

	bl_period_mask = (1 << bl_int_count) - 1;
	bl_period &= bl_period_mask;

	bl_pwm_mask = bl_period_mask << (16 - bl_int_count);

	if (fractional_duty_cycle_en == 0)
	bl_pwm &= bl_pwm_mask;
	else
	bl_pwm &= 0xFFFF;

	current_backlight = (uint64_t)bl_pwm << (1 + bl_int_count);

	if (bl_period == 0)
	bl_period = 0xFFFF;

	current_backlight = div_u64(current_backlight, bl_period);
	current_backlight = (current_backlight + 1) >> 1;

	current_backlight = (uint64_t)(current_backlight) * bl_period;

	round_result = (uint32_t)(current_backlight & 0xFFFFFFFF);

	round_result = (round_result >> (bl_int_count-1)) & 1;

	current_backlight >>= bl_int_count;
	current_backlight += round_result;

	return (uint32_t)(current_backlight);
	}

	static uint32_t dce_panel_cntl_hw_init(struct panel_cntl *panel_cntl)
	{
	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);
	uint32_t value;
	uint32_t current_backlight;

	/* It must not be 0, so we have to restore them
	* Bios bug w/a - period resets to zero,
	* restoring to cache values which is always correct
	*/
	REG_GET(BL_PWM_CNTL, BL_ACTIVE_INT_FRAC_CNT, &value);

	if (value == 0 \|\| value == 1) {
	if (panel_cntl->stored_backlight_registers.BL_PWM_CNTL != 0) {
	REG_WRITE(BL_PWM_CNTL,
	panel_cntl->stored_backlight_registers.BL_PWM_CNTL);
	REG_WRITE(BL_PWM_CNTL2,
	panel_cntl->stored_backlight_registers.BL_PWM_CNTL2);
	REG_WRITE(BL_PWM_PERIOD_CNTL,
	panel_cntl->stored_backlight_registers.BL_PWM_PERIOD_CNTL);
	REG_UPDATE(PWRSEQ_REF_DIV,
	BL_PWM_REF_DIV,
	panel_cntl->stored_backlight_registers.LVTMA_PWRSEQ_REF_DIV_BL_PWM_REF_DIV);
	} else {
	/* TODO: Note: This should not really happen since VBIOS
	* should have initialized PWM registers on boot.
	*/
	REG_WRITE(BL_PWM_CNTL, 0xC000FA00);
	REG_WRITE(BL_PWM_PERIOD_CNTL, 0x000C0FA0);
	}
	} else {
	panel_cntl->stored_backlight_registers.BL_PWM_CNTL =
	REG_READ(BL_PWM_CNTL);
	panel_cntl->stored_backlight_registers.BL_PWM_CNTL2 =
	REG_READ(BL_PWM_CNTL2);
	panel_cntl->stored_backlight_registers.BL_PWM_PERIOD_CNTL =
	REG_READ(BL_PWM_PERIOD_CNTL);

	REG_GET(PWRSEQ_REF_DIV, BL_PWM_REF_DIV,
	&panel_cntl->stored_backlight_registers.LVTMA_PWRSEQ_REF_DIV_BL_PWM_REF_DIV);
	}

	// Have driver take backlight control
	// TakeBacklightControl(true)
	value = REG_READ(BIOS_SCRATCH_2);
	value \|= ATOM_S2_VRI_BRIGHT_ENABLE;
	REG_WRITE(BIOS_SCRATCH_2, value);

	// Enable the backlight output
	REG_UPDATE(BL_PWM_CNTL, BL_PWM_EN, 1);

	// Unlock group 2 backlight registers
	REG_UPDATE(BL_PWM_GRP1_REG_LOCK,
	BL_PWM_GRP1_REG_LOCK, 0);

	current_backlight = dce_get_16_bit_backlight_from_pwm(panel_cntl);

	return current_backlight;
	}

	static bool dce_is_panel_backlight_on(struct panel_cntl *panel_cntl)
	{
	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);
	uint32_t blon, blon_ovrd, pwrseq_target_state;

	REG_GET_2(PWRSEQ_CNTL, LVTMA_BLON, &blon, LVTMA_BLON_OVRD, &blon_ovrd);
	REG_GET(PWRSEQ_CNTL, LVTMA_PWRSEQ_TARGET_STATE, &pwrseq_target_state);

	if (blon_ovrd)
	return blon;
	else
	return pwrseq_target_state;
	}

	static bool dce_is_panel_powered_on(struct panel_cntl *panel_cntl)
	{
	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);
	uint32_t pwr_seq_state, dig_on, dig_on_ovrd;

	REG_GET(PWRSEQ_STATE, LVTMA_PWRSEQ_TARGET_STATE_R, &pwr_seq_state);

	REG_GET_2(PWRSEQ_CNTL, LVTMA_DIGON, &dig_on, LVTMA_DIGON_OVRD, &dig_on_ovrd);

	return (pwr_seq_state == 1) \|\| (dig_on == 1 && dig_on_ovrd == 1);
	}

	static void dce_store_backlight_level(struct panel_cntl *panel_cntl)
	{
	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);

	panel_cntl->stored_backlight_registers.BL_PWM_CNTL =
	REG_READ(BL_PWM_CNTL);
	panel_cntl->stored_backlight_registers.BL_PWM_CNTL2 =
	REG_READ(BL_PWM_CNTL2);
	panel_cntl->stored_backlight_registers.BL_PWM_PERIOD_CNTL =
	REG_READ(BL_PWM_PERIOD_CNTL);

	REG_GET(PWRSEQ_REF_DIV, BL_PWM_REF_DIV,
	&panel_cntl->stored_backlight_registers.LVTMA_PWRSEQ_REF_DIV_BL_PWM_REF_DIV);
	}

	static void dce_driver_set_backlight(struct panel_cntl *panel_cntl,
	uint32_t backlight_pwm_u16_16)
	{
	uint32_t backlight_16bit;
	uint32_t masked_pwm_period;
	uint8_t bit_count;
	uint64_t active_duty_cycle;
	uint32_t pwm_period_bitcnt;
	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);

	/*
	* 1. Find 16 bit backlight active duty cycle, where 0 <= backlight
	* active duty cycle <= backlight period
	*/

	/* 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,
	BL_PWM_PERIOD, &masked_pwm_period);

	if (pwm_period_bitcnt == 0)
	bit_count = 16;
	else
	bit_count = pwm_period_bitcnt;

	/* e.g. maskedPwmPeriod = 0x24 when bitCount is 6 */
	masked_pwm_period = masked_pwm_period & ((1 << bit_count) - 1);

	/* 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_pwm_u16_16 * masked_pwm_period;

	/* 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
	*/
	backlight_16bit = active_duty_cycle >> bit_count;
	backlight_16bit &= 0xFFFF;
	backlight_16bit += (active_duty_cycle >> (bit_count - 1)) & 0x1;

	/*
	* 2. Program register with updated value
	*/

	/* 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);

	// 2.2 Write new active duty cycle
	REG_UPDATE(BL_PWM_CNTL, BL_ACTIVE_INT_FRAC_CNT, backlight_16bit);

	/* 2.3 Unlock group 2 backlight registers */
	REG_UPDATE(BL_PWM_GRP1_REG_LOCK,
	BL_PWM_GRP1_REG_LOCK, 0);

	/* 3 Wait for pending bit to be cleared */
	REG_WAIT(BL_PWM_GRP1_REG_LOCK,
	BL_PWM_GRP1_REG_UPDATE_PENDING, 0,
	1, 10000);
	}

	static void dce_panel_cntl_destroy(struct panel_cntl **panel_cntl)
	{
	struct dce_panel_cntl dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);

	kfree(dce_panel_cntl);
	*panel_cntl = NULL;
	}

	static const struct panel_cntl_funcs dce_link_panel_cntl_funcs = {
	.destroy = dce_panel_cntl_destroy,
	.hw_init = dce_panel_cntl_hw_init,
	.is_panel_backlight_on = dce_is_panel_backlight_on,
	.is_panel_powered_on = dce_is_panel_powered_on,
	.store_backlight_level = dce_store_backlight_level,
	.driver_set_backlight = dce_driver_set_backlight,
	.get_current_backlight = dce_get_16_bit_backlight_from_pwm,
	};

	void dce_panel_cntl_construct(
	struct dce_panel_cntl *dce_panel_cntl,
	const struct panel_cntl_init_data *init_data,
	const struct dce_panel_cntl_registers *regs,
	const struct dce_panel_cntl_shift *shift,
	const struct dce_panel_cntl_mask *mask)
	{
	struct panel_cntl *base = &dce_panel_cntl->base;

	base->stored_backlight_registers.BL_PWM_CNTL = 0;
	base->stored_backlight_registers.BL_PWM_CNTL2 = 0;
	base->stored_backlight_registers.BL_PWM_PERIOD_CNTL = 0;
	base->stored_backlight_registers.LVTMA_PWRSEQ_REF_DIV_BL_PWM_REF_DIV = 0;

	dce_panel_cntl->regs = regs;
	dce_panel_cntl->shift = shift;
	dce_panel_cntl->mask = mask;

	dce_panel_cntl->base.funcs = &dce_link_panel_cntl_funcs;
	dce_panel_cntl->base.ctx = init_data->ctx;
	dce_panel_cntl->base.inst = init_data->inst;
	}