[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <CAMRc=Mcj3YpHqFqdGPF7YXRHz=56J73TV2oPm70SHUmgXRAy=A@mail.gmail.com>
Date: Wed, 1 Oct 2025 05:24:01 -0700
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Alex Tran <alex.t.tran@...il.com>
Cc: Bartosz Golaszewski <brgl@...ev.pl>, linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v1] gpio: gpio-grgpio: call request_irq after incrementing
the reference count
On Sun, 28 Sep 2025 07:40:19 +0200, Alex Tran <alex.t.tran@...il.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@...il.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
>
>
Powered by blists - more mailing lists