On Thu, Jul 08, 2021 at 11:10:58AM +0200, Marek Vasut wrote:
The note in c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c") says that gpio-backlight uses brightness as power state. Other backlight drivers do not, so limit this workaround to gpio-backlight.
This fixes the case where e.g. pwm-backlight can perfectly well be set to brightness 0 on boot in DT, which without this patch leads to the display brightness to be max instead of off.
Fixes: c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c") Signed-off-by: Marek Vasut marex@denx.de Cc: Daniel Thompson daniel.thompson@linaro.org Cc: Meghana Madhyastha meghana.madhyastha@gmail.com Cc: Noralf Trønnes noralf@tronnes.org Cc: Sean Paul seanpaul@chromium.org Cc: Thierry Reding treding@nvidia.com
I have to admit that this patch really does makes it clear just how nasty the hack in of_find_backlight() currently is.
Moreover I think it is also be obsolete. gpio-backlight power mode handling was pretty broken when this code was introduced. It was fixed in 2019 by ec665b756e6f ("backlight: gpio backlight: Correct initial power state handling") by trying to match the behaviour of PWM backlight. The new code always sets the brightness to 1 so I think we can just remove the hack from of_find_backlight() since I think it is unreachable.
Daniel.
drivers/video/backlight/backlight.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 537fe1b376ad7..dfb66171dec41 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -676,6 +676,7 @@ EXPORT_SYMBOL(of_find_backlight_by_node); static struct backlight_device *of_find_backlight(struct device *dev) { struct backlight_device *bd = NULL;
bool is_gpio_backlight = false; struct device_node *np;
if (!dev)
@@ -685,6 +686,8 @@ static struct backlight_device *of_find_backlight(struct device *dev) np = of_parse_phandle(dev->of_node, "backlight", 0); if (np) { bd = of_find_backlight_by_node(np);
is_gpio_backlight =of_device_is_compatible(np, "gpio-backlight"); of_node_put(np); if (!bd) return ERR_PTR(-EPROBE_DEFER);@@ -692,7 +695,7 @@ static struct backlight_device *of_find_backlight(struct device *dev) * Note: gpio_backlight uses brightness as * power state during probe */
if (!bd->props.brightness)
if (is_gpio_backlight && !bd->props.brightness) bd->props.brightness = bd->props.max_brightness;-- 2.30.2