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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: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
This commit is contained in:
Philipp Zabel 2015-11-18 18:12:25 +01:00 committed by Lee Jones
parent 86c68e2fb3
commit 3698d7e7d2
1 changed files with 22 additions and 1 deletions
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23
drivers/video/backlight/pwm_bl.c
View File

@ -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);