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Commit 3698d7e7 authored by Philipp Zabel's avatar Philipp Zabel Committed by Lee Jones
Browse files

backlight: pwm_bl: Avoid backlight flicker when probed from DT 



If the driver is probed from the device tree, and there is a phandle
property set on it, and the enable GPIO is already configured as output,
and the backlight is currently disabled, keep it disabled.
If all these conditions are met, assume there will be some other driver
that can enable the backlight at the appropriate time.

Signed-off-by: default avatarPhilipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: default avatarChristian Gmeiner <christian.gmeiner@gmail.com>
Tested-by: default avatarHeiko Stuebner <heiko@sntech.de>
Signed-off-by: default avatarLee Jones <lee.jones@linaro.org>
parent 86c68e2f

drivers/video/backlight/pwm_bl.c

+22 −1
Original line number Diff line number Diff line
@@ -199,6 +199,8 @@ static int pwm_backlight_probe(struct platform_device *pdev) 
	struct backlight_properties props;

	struct backlight_device *bl;

	struct pwm_bl_data *pb;

	phandle phandle = pdev->dev.of_node->phandle;

	int initial_blank = FB_BLANK_UNBLANK;

	int ret;



	if (!data) {
@@ -242,7 +244,7 @@ static int pwm_backlight_probe(struct platform_device *pdev) 
	pb->enabled = false;



	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",

						  GPIOD_OUT_HIGH);

						  GPIOD_ASIS);

	if (IS_ERR(pb->enable_gpio)) {

		ret = PTR_ERR(pb->enable_gpio);

		goto err_alloc;
@@ -264,12 +266,30 @@ static int pwm_backlight_probe(struct platform_device *pdev) 
		pb->enable_gpio = gpio_to_desc(data->enable_gpio);

	}



	if (pb->enable_gpio) {

		/*

		 * If the driver is probed from the device tree and there is a

		 * phandle link pointing to the backlight node, it is safe to

		 * assume that another driver will enable the backlight at the

		 * appropriate time. Therefore, if it is disabled, keep it so.

		 */

		if (phandle &&

		    gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT &&

		    gpiod_get_value(pb->enable_gpio) == 0)

			initial_blank = FB_BLANK_POWERDOWN;

		else

			gpiod_direction_output(pb->enable_gpio, 1);

	}



	pb->power_supply = devm_regulator_get(&pdev->dev, "power");

	if (IS_ERR(pb->power_supply)) {

		ret = PTR_ERR(pb->power_supply);

		goto err_alloc;

	}



	if (phandle && !regulator_is_enabled(pb->power_supply))

		initial_blank = FB_BLANK_POWERDOWN;



	pb->pwm = devm_pwm_get(&pdev->dev, NULL);

	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER

	    && !pdev->dev.of_node) {
@@ -320,6 +340,7 @@ static int pwm_backlight_probe(struct platform_device *pdev) 
	}



	bl->props.brightness = data->dft_brightness;

	bl->props.power = initial_blank;

	backlight_update_status(bl);



	platform_set_drvdata(pdev, bl);