[PATCH v2] drm/bridge: samsung-dsim: fix TE GPIO lifetime for host attach

[PATCH v2] drm/bridge: samsung-dsim: fix TE GPIO lifetime for host attach

[Li Youhong]

From: Li Youhong <liyouhong@kylinos.cn>

When the Exynos DSI driver was generalized into samsung-dsim, the TE
GPIO acquisition was switched from gpiod_get_optional() to
devm_gpiod_get_optional() while keeping the matching gpiod_put() calls.
That combination is wrong for a managed descriptor.

However, dropping the puts and keeping the managed get is also wrong:
samsung_dsim_register_te_irq() runs from the DSI host attach callback,
and host detach/reattach can happen without destroying the device that
owns the managed action. A second attach would then request the GPIO
again without having released it.

Switch back to a non-managed gpiod_get_optional() and keep the explicit
gpiod_put() on the request_irq() error path and in
samsung_dsim_unregister_te_irq().

Fixes: e7447128ca4a ("drm: bridge: Generalize Exynos-DSI driver into a Samsung DSIM bridge")
Suggested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Li Youhong <liyouhong@kylinos.cn>
---
v2:
- Prefer non-devm gpiod_get_optional() and keep gpiod_put(), because TE
  GPIO is acquired in host attach and must be released on host detach

 drivers/gpu/drm/bridge/samsung-dsim.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1862,7 +1862,8 @@ static int samsung_dsim_register_te_irq(struct samsung_dsim *dsi, struct device
 	int te_gpio_irq;
 	int ret;
 
-	dsi->te_gpio = devm_gpiod_get_optional(dev, "te", GPIOD_IN);
+	/* Released on host detach; do not use the managed get. */
+	dsi->te_gpio = gpiod_get_optional(dev, "te", GPIOD_IN);
 	if (!dsi->te_gpio)
 		return 0;
 	else if (IS_ERR(dsi->te_gpio))
-- 
2.25.1

Re: [PATCH v2] drm/bridge: samsung-dsim: fix TE GPIO lifetime for host attach

[Luca Ceresoli]

Hello Li,

On Fri Sep 4, 2026 at 3:49 AM CEST, Li Youhong wrote:
> From: Li Youhong <liyouhong@kylinos.cn>
>
> When the Exynos DSI driver was generalized into samsung-dsim, the TE
> GPIO acquisition was switched from gpiod_get_optional() to
> devm_gpiod_get_optional() while keeping the matching gpiod_put() calls.
> That combination is wrong for a managed descriptor.
>
> However, dropping the puts and keeping the managed get is also wrong:
> samsung_dsim_register_te_irq() runs from the DSI host attach callback,
> and host detach/reattach can happen without destroying the device that
> owns the managed action. A second attach would then request the GPIO
> again without having released it.
>
> Switch back to a non-managed gpiod_get_optional() and keep the explicit
> gpiod_put() on the request_irq() error path and in
> samsung_dsim_unregister_te_irq().
>
> Fixes: e7447128ca4a ("drm: bridge: Generalize Exynos-DSI driver into a Samsung DSIM bridge")
> Suggested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
> Signed-off-by: Li Youhong <liyouhong@kylinos.cn>
> ---
> v2:
> - Prefer non-devm gpiod_get_optional() and keep gpiod_put(), because TE
>   GPIO is acquired in host attach and must be released on host detach
>
>  drivers/gpu/drm/bridge/samsung-dsim.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> @@ -1862,7 +1862,8 @@ static int samsung_dsim_register_te_irq(struct samsung_dsim *dsi, struct device
>  	int te_gpio_irq;
>  	int ret;
>
> -	dsi->te_gpio = devm_gpiod_get_optional(dev, "te", GPIOD_IN);
> +	/* Released on host detach; do not use the managed get. */
> +	dsi->te_gpio = gpiod_get_optional(dev, "te", GPIOD_IN);

The comment is not really needed, this should be obvious by reading the
code. No need to resend just for that, I can remove it while applying.

Other than that it's OK:
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com