[PATCH v1] gpio: gpio-grgpio: call request_irq after incrementing the reference count

[PATCH v1] gpio: gpio-grgpio: call request_irq after incrementing the reference count

[Alex Tran]

Remove extraneous dropping of the lock just to call 'request_irq'
and locking again afterwards. Increment reference count
before calling 'request_irq'. Rollback reference count if
'request_irq' fails.

Signed-off-by: Alex Tran <alex.t.tran@gmail.com>
---
 drivers/gpio/gpio-grgpio.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/gpio/gpio-grgpio.c b/drivers/gpio/gpio-grgpio.c
index 0c0f97fa14fc..18d972fddfac 100644
--- a/drivers/gpio/gpio-grgpio.c
+++ b/drivers/gpio/gpio-grgpio.c
@@ -227,6 +227,7 @@ static int grgpio_irq_map(struct irq_domain *d, unsigned int irq,
 	struct grgpio_priv *priv = d->host_data;
 	struct grgpio_lirq *lirq;
 	struct grgpio_uirq *uirq;
+	bool needs_req = false;
 	unsigned long flags;
 	int offset = hwirq;
 	int ret = 0;
@@ -242,30 +243,28 @@ static int grgpio_irq_map(struct irq_domain *d, unsigned int irq,
 		irq, offset);
 
 	gpio_generic_chip_lock_irqsave(&priv->chip, flags);
-
-	/* Request underlying irq if not already requested */
 	lirq->irq = irq;
 	uirq = &priv->uirqs[lirq->index];
-	if (uirq->refcnt == 0) {
-		/*
-		 * FIXME: This is not how locking works at all, you can't just
-		 * release the lock for a moment to do something that can't
-		 * sleep...
-		 */
-		gpio_generic_chip_unlock_irqrestore(&priv->chip, flags);
+	needs_req = (uirq->refcnt == 0);
+	uirq->refcnt++;
+	gpio_generic_chip_unlock_irqrestore(&priv->chip, flags);
+
+	/* Request underlying irq if not already requested */
+	if (needs_req) {
 		ret = request_irq(uirq->uirq, grgpio_irq_handler, 0,
 				  dev_name(priv->dev), priv);
 		if (ret) {
 			dev_err(priv->dev,
 				"Could not request underlying irq %d\n",
 				uirq->uirq);
+
+			// rollback
+			gpio_generic_chip_lock_irqsave(&priv->chip, flags);
+			uirq->refcnt--;
+			gpio_generic_chip_unlock_irqrestore(&priv->chip, flags);
 			return ret;
 		}
-		gpio_generic_chip_lock_irqsave(&priv->chip, flags);
 	}
-	uirq->refcnt++;
-
-	gpio_generic_chip_unlock_irqrestore(&priv->chip, flags);
 
 	/* Setup irq  */
 	irq_set_chip_data(irq, priv);
-- 
2.51.0

Re: [PATCH v1] gpio: gpio-grgpio: call request_irq after incrementing the reference count

[Linus Walleij]

On Sun, Sep 28, 2025 at 7:41 AM Alex Tran <alex.t.tran@gmail.com> wrote:

> Remove extraneous dropping of the lock just to call 'request_irq'
> and locking again afterwards. Increment reference count
> before calling 'request_irq'. Rollback reference count if
> 'request_irq' fails.
>
> Signed-off-by: Alex Tran <alex.t.tran@gmail.com>

This looks right.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

Re: [PATCH v1] gpio: gpio-grgpio: call request_irq after incrementing the reference count

[Bartosz Golaszewski]

On Sun, 28 Sep 2025 07:40:19 +0200, Alex Tran <alex.t.tran@gmail.com> said:
> Remove extraneous dropping of the lock just to call 'request_irq'
> and locking again afterwards. Increment reference count
> before calling 'request_irq'. Rollback reference count if
> 'request_irq' fails.
>
> Signed-off-by: Alex Tran <alex.t.tran@gmail.com>
> ---
>  drivers/gpio/gpio-grgpio.c | 25 ++++++++++++-------------
>  1 file changed, 12 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpio/gpio-grgpio.c b/drivers/gpio/gpio-grgpio.c
> index 0c0f97fa14fc..18d972fddfac 100644
> --- a/drivers/gpio/gpio-grgpio.c
> +++ b/drivers/gpio/gpio-grgpio.c
> @@ -227,6 +227,7 @@ static int grgpio_irq_map(struct irq_domain *d, unsigned int irq,
>  	struct grgpio_priv *priv = d->host_data;
>  	struct grgpio_lirq *lirq;
>  	struct grgpio_uirq *uirq;
> +	bool needs_req = false;
>  	unsigned long flags;
>  	int offset = hwirq;
>  	int ret = 0;
> @@ -242,30 +243,28 @@ static int grgpio_irq_map(struct irq_domain *d, unsigned int irq,
>  		irq, offset);
>
>  	gpio_generic_chip_lock_irqsave(&priv->chip, flags);
> -
> -	/* Request underlying irq if not already requested */
>  	lirq->irq = irq;
>  	uirq = &priv->uirqs[lirq->index];
> -	if (uirq->refcnt == 0) {
> -		/*
> -		 * FIXME: This is not how locking works at all, you can't just
> -		 * release the lock for a moment to do something that can't
> -		 * sleep...
> -		 */
> -		gpio_generic_chip_unlock_irqrestore(&priv->chip, flags);
> +	needs_req = (uirq->refcnt == 0);
> +	uirq->refcnt++;

Any chance this could be made to use atomic_t instead?

Like:

if (atomic_fetch_add(1, &priv->uirqs) == 0) {
	request_irq()
	...
}

?

Bart

> +	gpio_generic_chip_unlock_irqrestore(&priv->chip, flags);
> +
> +	/* Request underlying irq if not already requested */
> +	if (needs_req) {
>  		ret = request_irq(uirq->uirq, grgpio_irq_handler, 0,
>  				  dev_name(priv->dev), priv);
>  		if (ret) {
>  			dev_err(priv->dev,
>  				"Could not request underlying irq %d\n",
>  				uirq->uirq);
> +
> +			// rollback
> +			gpio_generic_chip_lock_irqsave(&priv->chip, flags);
> +			uirq->refcnt--;
> +			gpio_generic_chip_unlock_irqrestore(&priv->chip, flags);
>  			return ret;
>  		}
> -		gpio_generic_chip_lock_irqsave(&priv->chip, flags);
>  	}
> -	uirq->refcnt++;
> -
> -	gpio_generic_chip_unlock_irqrestore(&priv->chip, flags);
>
>  	/* Setup irq  */
>  	irq_set_chip_data(irq, priv);
> --
> 2.51.0
>
>

Re: [PATCH v1] gpio: gpio-grgpio: call request_irq after incrementing the reference count

[Alex Tran]

> Any chance this could be made to use atomic_t instead?
>
> Like:
>
> if (atomic_fetch_add(1, &priv->uirqs) == 0) {
>         request_irq()
>         ...
> }
>
> ?
>
> Bart

Sure, the reference count can be converted to atomic_t. I'll follow up
with a v2 patch.

Thanks,
-- 
Alex Tran