From 3698d7e7d221a5c90d4b55e96d0c8f98a8b4d7df Mon Sep 17 00:00:00 2001
From: Philipp Zabel
Date: Wed, 18 Nov 2015 18:12:25 +0100
Subject: 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
Reviewed-by: Christian Gmeiner
Tested-by: Heiko Stuebner
Signed-off-by: Lee Jones
---
drivers/video/backlight/pwm_bl.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)
(limited to 'drivers/video')
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);
--
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