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

Commit Message

Liu Ying July 21, 2023, 8:58 a.m. UTC

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 <[e-mail]>
---
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(-)

Comments

Andy Shevchenko July 21, 2023, 9:10 a.m. UTC | #1

On Fri, Jul 21, 2023 at 11:58 AM Ying Liu <[e-mail]> 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 <[e-mail]>

Patch

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;