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SubjectRe: [PATCH v2 1/4] gpio: gpiolib: Allow GPIO IRQs to lazy disable
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Quoting Maulik Shah (2020-05-23 10:11:10)
> With 'commit 461c1a7d4733 ("gpiolib: override irq_enable/disable")' gpiolib
> overrides irqchip's irq_enable and irq_disable callbacks. If irq_disable
> callback is implemented then genirq takes unlazy path to disable irq.
>
> Underlying irqchip may not want to implement irq_disable callback to lazy
> disable irq when client drivers invokes disable_irq(). By overriding
> irq_disable callback, gpiolib ends up always unlazy disabling IRQ.
>
> Allow gpiolib to lazy disable IRQs by overriding irq_disable callback only
> if irqchip implemented irq_disable. In cases where irq_disable is not
> implemented irq_mask is overridden. Similarly override irq_enable callback
> only if irqchip implemented irq_enable otherwise irq_unmask is overridden.
>
> Fixes: 461c1a7d47 (gpiolib: override irq_enable/disable)

This isn't a proper Fixes line. Should have quotes

Fixes: 461c1a7d4733 ("gpiolib: override irq_enable/disable")

> Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
> ---
> drivers/gpio/gpiolib.c | 55 +++++++++++++++++++++++++++++----------------
> include/linux/gpio/driver.h | 13 +++++++++++
> 2 files changed, 49 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index eaa0e20..3810cd0 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -2465,32 +2465,37 @@ static void gpiochip_irq_relres(struct irq_data *d)
> gpiochip_relres_irq(gc, d->hwirq);
> }
>
> +static void gpiochip_irq_mask(struct irq_data *d)
> +{
> + struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
> +
> + if (gc->irq.irq_mask)
> + gc->irq.irq_mask(d);
> + gpiochip_disable_irq(gc, d->hwirq);

How does this work in the lazy case when I want to drive the GPIO? Say I
have a GPIO that is also an interrupt. The code would look like

struct gpio_desc *gpio = gpiod_get(...)
unsigned int girq = gpiod_to_irq(gpio)

request_irq(girq, ...);

disable_irq(girq);
gpiod_direction_output(gpio, 1);

In the lazy case genirq wouldn't call the mask function until the first
interrupt arrived on the GPIO line. If that never happened then wouldn't
we be blocked in gpiod_direction_output() when the test_bit() sees
FLAG_USED_AS_IRQ? Or do we need irqs to be released before driving
gpios?

> +}
> +
> +static void gpiochip_irq_unmask(struct irq_data *d)
> +{
> + struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
> +
> + gpiochip_enable_irq(gc, d->hwirq);
> + if (gc->irq.irq_unmask)
> + gc->irq.irq_unmask(d);
> +}
> +

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