Re: [PATCH 2/2] drm/bridge: ti-sn65dsi86: Expose backlight controls

[Steev Klimaszewski]

On 9/30/20 5:35 PM, Bjorn Andersson wrote:
> The TI SN65DSI86 can be configured to generate a PWM pulse on GPIO4,
> to be used to drive a backlight driver.
>
> Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
> ---
>  drivers/gpu/drm/bridge/Kconfig        |   1 +
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 143 +++++++++++++++++++++++++-
>  2 files changed, 140 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index 43271c21d3fc..eea310bd88e1 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -195,6 +195,7 @@ config DRM_TI_SN65DSI86
>  	select REGMAP_I2C
>  	select DRM_PANEL
>  	select DRM_MIPI_DSI
> +	select BACKLIGHT_CLASS_DEVICE
>  	help
>  	  Texas Instruments SN65DSI86 DSI to eDP Bridge driver
>  
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> index 5b6e19ecbc84..41e24d0dbd18 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> @@ -68,6 +68,7 @@
>  #define  SN_GPIO_MUX_OUTPUT			1
>  #define  SN_GPIO_MUX_SPECIAL			2
>  #define  SN_GPIO_MUX_MASK			0x3
> +#define  SN_GPIO_MUX_SHIFT(gpio)		((gpio) * 2)
>  #define SN_AUX_WDATA_REG(x)			(0x64 + (x))
>  #define SN_AUX_ADDR_19_16_REG			0x74
>  #define SN_AUX_ADDR_15_8_REG			0x75
> @@ -86,6 +87,12 @@
>  #define SN_ML_TX_MODE_REG			0x96
>  #define  ML_TX_MAIN_LINK_OFF			0
>  #define  ML_TX_NORMAL_MODE			BIT(0)
> +#define SN_PWM_PRE_DIV_REG			0xA0
> +#define SN_BACKLIGHT_SCALE_REG			0xA1
> +#define SN_BACKLIGHT_REG			0xA3
> +#define SN_PWM_CTL_REG				0xA5
> +#define  SN_PWM_ENABLE				BIT(1)
> +#define  SN_PWM_INVERT				BIT(0)
>  #define SN_AUX_CMD_STATUS_REG			0xF4
>  #define  AUX_IRQ_STATUS_AUX_RPLY_TOUT		BIT(3)
>  #define  AUX_IRQ_STATUS_AUX_SHORT		BIT(5)
> @@ -155,6 +162,8 @@ struct ti_sn_bridge {
>  	struct gpio_chip		gchip;
>  	DECLARE_BITMAP(gchip_output, SN_NUM_GPIOS);
>  #endif
> +	u32				brightness;
> +	u32				max_brightness;
>  };
>  
>  static const struct regmap_range ti_sn_bridge_volatile_ranges[] = {
> @@ -173,6 +182,18 @@ static const struct regmap_config ti_sn_bridge_regmap_config = {
>  	.cache_type = REGCACHE_NONE,
>  };
>  
> +static void ti_sn_bridge_read_u16(struct ti_sn_bridge *pdata,
> +				  unsigned int reg, u16 *val)
> +{
> +	unsigned int high;
> +	unsigned int low;
> +
> +	regmap_read(pdata->regmap, reg, &low);
> +	regmap_read(pdata->regmap, reg + 1, &high);
> +
> +	*val = high << 8 | low;
> +}
> +
>  static void ti_sn_bridge_write_u16(struct ti_sn_bridge *pdata,
>  				   unsigned int reg, u16 val)
>  {
> @@ -180,6 +201,50 @@ static void ti_sn_bridge_write_u16(struct ti_sn_bridge *pdata,
>  	regmap_write(pdata->regmap, reg + 1, val >> 8);
>  }
>  
> +static int ti_sn_backlight_update(struct ti_sn_bridge *pdata)
> +{
> +	unsigned int pre_div;
> +
> +	if (!pdata->max_brightness)
> +		return 0;
> +
> +	/* Enable PWM on GPIO4 */
> +	regmap_update_bits(pdata->regmap, SN_GPIO_CTRL_REG,
> +			   SN_GPIO_MUX_MASK << SN_GPIO_MUX_SHIFT(4 - 1),
> +			   SN_GPIO_MUX_SPECIAL << SN_GPIO_MUX_SHIFT(4 - 1));
> +
> +	if (pdata->brightness) {
> +		/* Set max brightness */
> +		ti_sn_bridge_write_u16(pdata, SN_BACKLIGHT_SCALE_REG, pdata->max_brightness);
> +
> +		/* Set brightness */
> +		ti_sn_bridge_write_u16(pdata, SN_BACKLIGHT_REG, pdata->brightness);
> +
> +		/*
> +		 * The PWM frequency is derived from the refclk as:
> +		 * PWM_FREQ = REFCLK_FREQ / (PWM_PRE_DIV * BACKLIGHT_SCALE + 1)
> +		 *
> +		 * A hand wavy estimate based on 12MHz refclk and 500Hz desired
> +		 * PWM frequency gives us a pre_div resulting in a PWM
> +		 * frequency of between 500 and 1600Hz, depending on the actual
> +		 * refclk rate.
> +		 *
> +		 * One is added to avoid high BACKLIGHT_SCALE values to produce
> +		 * a pre_div of 0 - which cancels out the large BACKLIGHT_SCALE
> +		 * value.
> +		 */
> +		pre_div = 12000000 / (500 * pdata->max_brightness) + 1;
> +		regmap_write(pdata->regmap, SN_PWM_PRE_DIV_REG, pre_div);
> +
> +		/* Enable PWM */
> +		regmap_update_bits(pdata->regmap, SN_PWM_CTL_REG, SN_PWM_ENABLE, SN_PWM_ENABLE);
> +	} else {
> +		regmap_update_bits(pdata->regmap, SN_PWM_CTL_REG, SN_PWM_ENABLE, 0);
> +	}
> +
> +	return 0;
> +}
> +
>  static int __maybe_unused ti_sn_bridge_resume(struct device *dev)
>  {
>  	struct ti_sn_bridge *pdata = dev_get_drvdata(dev);
> @@ -193,7 +258,7 @@ static int __maybe_unused ti_sn_bridge_resume(struct device *dev)
>  
>  	gpiod_set_value(pdata->enable_gpio, 1);
>  
> -	return ret;
> +	return ti_sn_backlight_update(pdata);
>  }
>  
>  static int __maybe_unused ti_sn_bridge_suspend(struct device *dev)
> @@ -1010,7 +1075,7 @@ static int ti_sn_bridge_gpio_direction_input(struct gpio_chip *chip,
>  					     unsigned int offset)
>  {
>  	struct ti_sn_bridge *pdata = gpiochip_get_data(chip);
> -	int shift = offset * 2;
> +	int shift = SN_GPIO_MUX_SHIFT(offset);
>  	int ret;
>  
>  	if (!test_and_clear_bit(offset, pdata->gchip_output))
> @@ -1038,7 +1103,7 @@ static int ti_sn_bridge_gpio_direction_output(struct gpio_chip *chip,
>  					      unsigned int offset, int val)
>  {
>  	struct ti_sn_bridge *pdata = gpiochip_get_data(chip);
> -	int shift = offset * 2;
> +	int shift = SN_GPIO_MUX_SHIFT(offset);
>  	int ret;
>  
>  	if (test_and_set_bit(offset, pdata->gchip_output))
> @@ -1073,12 +1138,17 @@ static const char * const ti_sn_bridge_gpio_names[SN_NUM_GPIOS] = {
>  
>  static int ti_sn_setup_gpio_controller(struct ti_sn_bridge *pdata)
>  {
> +	int ngpio = SN_NUM_GPIOS;
>  	int ret;
>  
>  	/* Only init if someone is going to use us as a GPIO controller */
>  	if (!of_property_read_bool(pdata->dev->of_node, "gpio-controller"))
>  		return 0;
>  
> +	/* If GPIO4 is used for backlight, reduce number of gpios */
> +	if (pdata->max_brightness)
> +		ngpio--;
> +
>  	pdata->gchip.label = dev_name(pdata->dev);
>  	pdata->gchip.parent = pdata->dev;
>  	pdata->gchip.owner = THIS_MODULE;
> @@ -1092,7 +1162,7 @@ static int ti_sn_setup_gpio_controller(struct ti_sn_bridge *pdata)
>  	pdata->gchip.set = ti_sn_bridge_gpio_set;
>  	pdata->gchip.can_sleep = true;
>  	pdata->gchip.names = ti_sn_bridge_gpio_names;
> -	pdata->gchip.ngpio = SN_NUM_GPIOS;
> +	pdata->gchip.ngpio = ngpio;
>  	pdata->gchip.base = -1;
>  	ret = devm_gpiochip_add_data(pdata->dev, &pdata->gchip, pdata);
>  	if (ret)
> @@ -1159,6 +1229,65 @@ static void ti_sn_bridge_parse_lanes(struct ti_sn_bridge *pdata,
>  	pdata->ln_polrs = ln_polrs;
>  }
>  
> +static int ti_sn_backlight_update_status(struct backlight_device *bl)
> +{
> +	struct ti_sn_bridge *pdata = bl_get_data(bl);
> +	int brightness = bl->props.brightness;
> +
> +	if (bl->props.power != FB_BLANK_UNBLANK ||
> +	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
> +	    bl->props.state & BL_CORE_FBBLANK) {
> +		pdata->brightness = 0;
> +	}
> +
> +	pdata->brightness = brightness;
> +
> +	return ti_sn_backlight_update(pdata);
> +}
> +
> +static int ti_sn_backlight_get_brightness(struct backlight_device *bl)
> +{
> +	struct ti_sn_bridge *pdata = bl_get_data(bl);
> +	u16 val;
> +
> +	ti_sn_bridge_read_u16(pdata, SN_BACKLIGHT_REG, &val);
> +
> +	return val;
> +}
> +
> +const struct backlight_ops ti_sn_backlight_ops = {
> +	.update_status = ti_sn_backlight_update_status,
> +	.get_brightness = ti_sn_backlight_get_brightness,
> +};
> +
> +static int ti_sn_backlight_init(struct ti_sn_bridge *pdata)
> +{
> +	struct backlight_properties props = {};
> +	struct backlight_device	*bl;
> +	struct device *dev = pdata->dev;
> +	struct device_node *np = dev->of_node;
> +	int ret;
> +
> +	ret = of_property_read_u32(np, "ti,backlight-scale", &pdata->max_brightness);
> +	if (ret == -EINVAL) {
> +		return 0;
> +	} else if (ret || pdata->max_brightness >= 0xffff) {
> +		DRM_ERROR("invalid max-brightness\n");
> +		return -EINVAL;
> +	}
> +
> +	props.type = BACKLIGHT_RAW;
> +	props.max_brightness = pdata->max_brightness;
> +	bl = devm_backlight_device_register(dev, "sn65dsi86", dev, pdata,
> +					    &ti_sn_backlight_ops, &props);
> +	if (IS_ERR(bl)) {
> +		DRM_ERROR("failed to register backlight device\n");
> +		return PTR_ERR(bl);
> +	}
> +
> +	return 0;
> +}
> +
>  static int ti_sn_bridge_probe(struct i2c_client *client,
>  			      const struct i2c_device_id *id)
>  {
> @@ -1224,6 +1353,12 @@ static int ti_sn_bridge_probe(struct i2c_client *client,
>  
>  	pm_runtime_enable(pdata->dev);
>  
> +	ret = ti_sn_backlight_init(pdata);
> +	if (ret) {
> +		pm_runtime_disable(pdata->dev);
> +		return ret;
> +	}
> +
>  	ret = ti_sn_setup_gpio_controller(pdata);
>  	if (ret) {
>  		pm_runtime_disable(pdata->dev);


Tested-By: Steev Klimaszewski <steev@xxxxxxxx>