2023-07-21 09:26:29

by Liu Ying

Subject: [PATCH v3] backlight: gpio_backlight: Drop output gpio direction check for initial power state

If gpio pin is in input state but backlight is currently off due to
default pull downs, then initial power state is set to FB_BLANK_UNBLANK
in DT boot mode with phandle link and the backlight is effectively
turned on in gpio_backlight_probe(), which is undesirable according to
patch description of commit ec665b756e6f ("backlight: gpio-backlight:
Correct initial power state handling").

Quote:
---
If in DT boot we have phandle link then leave the GPIO in a state which the
bootloader left it and let the user of the backlight to configure it further.
---

So, let's drop output gpio direction check and only check gpio value to set
the initial power state.

Fixes: 706dc68102bc ("backlight: gpio: Explicitly set the direction of the GPIO")
Signed-off-by: Liu Ying <[email protected]>
---
v2->v3:
* Add Fixes tag. (Daniel)

v1->v2:
* Improve patch description. (Daniel, Bartosz, Andy)

drivers/video/backlight/gpio_backlight.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/video/backlight/gpio_backlight.c b/drivers/video/backlight/gpio_backlight.c
index 6f78d928f054..38c46936fdcd 100644
--- a/drivers/video/backlight/gpio_backlight.c
+++ b/drivers/video/backlight/gpio_backlight.c
@@ -87,8 +87,7 @@ static int gpio_backlight_probe(struct platform_device *pdev)
/* Not booted with device tree or no phandle link to the node */
bl->props.power = def_value ? FB_BLANK_UNBLANK
: FB_BLANK_POWERDOWN;
- else if (gpiod_get_direction(gbl->gpiod) == 0 &&
- gpiod_get_value_cansleep(gbl->gpiod) == 0)
+ else if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
bl->props.power = FB_BLANK_POWERDOWN;
else
bl->props.power = FB_BLANK_UNBLANK;
--
2.37.1

2023-07-21 09:39:02

by Andy Shevchenko

Subject: Re: [PATCH v3] backlight: gpio_backlight: Drop output gpio direction check for initial power state

On Fri, Jul 21, 2023 at 11:58 AM Ying Liu <[email protected]> wrote:
>
> If gpio pin is in input state but backlight is currently off due to

GPIO

> default pull downs, then initial power state is set to FB_BLANK_UNBLANK
> in DT boot mode with phandle link and the backlight is effectively
> turned on in gpio_backlight_probe(), which is undesirable according to
> patch description of commit ec665b756e6f ("backlight: gpio-backlight:
> Correct initial power state handling").
>
> Quote:

> ---
> If in DT boot we have phandle link then leave the GPIO in a state which the
> bootloader left it and let the user of the backlight to configure it further.
> ---

Just use ---8<--- or drop these completely, as your (commit message of
the) patch is broken now.

>
> So, let's drop output gpio direction check and only check gpio value to set

GPIO
GPIO

> the initial power state.
>
> Fixes: 706dc68102bc ("backlight: gpio: Explicitly set the direction of the GPIO")
> Signed-off-by: Liu Ying <[email protected]>

--
With Best Regards,
Andy Shevchenko