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authorPhilipp Zabel <p.zabel@pengutronix.de>2015-11-18 20:12:25 +0300
committerLee Jones <lee.jones@linaro.org>2016-01-11 08:56:22 +0300
commit3698d7e7d221a5c90d4b55e96d0c8f98a8b4d7df (patch)
tree02e7318028090532d74ba09bda5c353a0f3f3238 /drivers/video/backlight
parent86c68e2fb3eeb87ef716a0d61c5a346e9aee2ecb (diff)
downloadlinux-3698d7e7d221a5c90d4b55e96d0c8f98a8b4d7df.tar.xz
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>
Diffstat (limited to 'drivers/video/backlight')
-rw-r--r--drivers/video/backlight/pwm_bl.c23
1 files changed, 22 insertions, 1 deletions
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index ae3c6b6fd5db..3daf9cc9bc31 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -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);