Re: [PATCH v2 1/4] gpio: gpiolib: Allow GPIO IRQs to lazy disable

[Maulik Shah]

Hi,

On 5/27/2020 3:14 PM, Stephen Boyd wrote:
> 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")
Thanks for pointing this, i will address in next revision.
> > Signed-off-by: Maulik Shah <mkshah@xxxxxxxxxxxxxx>
> > ---
> >   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?

The client driver can decide to unlazy disable IRQ with below API...

Âirq_set_status_flags(girq, IRQ_DISABLE_UNLAZY);

This will immediatly invoke mask function (unlazy disable) from genirq, 
even though irq_disable is not implemented.

Thanks,
Maulik
> > +}
> > +
> > +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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