Re: [RFC PATCH V2 2/8] irqdomain: Don't set type when mapping an IRQ

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

Adding linux-gpio, so quoting in full.

On Thu, Dec 17, 2015 at 11:48 AM, Jon Hunter <jonathanh@xxxxxxxxxx> wrote:

> Some IRQ chips, such as GPIO controllers or secondary level interrupt
> controllers, may require require additional runtime power management
> control to ensure they are accessible. For such IRQ chips, it makes sense
> to enable the IRQ chip when interrupts are requested and disabled them
> again once all interrupts have been freed.
>
> When mapping an IRQ, the IRQ type settings are read and then programmed.
> The mapping of the IRQ happens before the IRQ is requested and so the
> programming of the type settings occurs before the IRQ is requested. This
> is a problem for IRQ chips that require additional power management
> control because they may not be accessible yet. Therefore, when mapping
> the IRQ, don't program the type settings, just save them and then program
> these saved settings when the IRQ is requested (so long as if they are not
> overridden via the call to request the IRQ).
>
> Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
> ---
>  kernel/irq/irqdomain.c | 18 ++++++++++++++----
>  kernel/irq/manage.c    |  7 +++++++
>  2 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> index eae31e978ab2..4322d6fd0b8f 100644
> --- a/kernel/irq/irqdomain.c
> +++ b/kernel/irq/irqdomain.c
> @@ -570,6 +570,7 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
>  {
>         struct device_node *of_node;
>         struct irq_domain *domain;
> +       struct irq_data *irq_data;
>         irq_hw_number_t hwirq;
>         unsigned int cur_type = IRQ_TYPE_NONE;
>         unsigned int type = IRQ_TYPE_NONE;
> @@ -634,10 +635,19 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
>                 return 0;
>         }
>
> -       /* Set type if specified and different than the current one */
> -       if (type != IRQ_TYPE_NONE &&
> -           type != irq_get_trigger_type(virq))
> -               irq_set_irq_type(virq, type);
> +       irq_data = irq_get_irq_data(virq);
> +       if (!irq_data) {
> +               if (irq_domain_is_hierarchy(domain))
> +                       irq_domain_free_irqs(virq, 1);
> +               else
> +                       irq_dispose_mapping(virq);
> +
> +               return 0;
> +       }
> +
> +       /* Store trigger type */
> +       irqd_set_trigger_type(irq_data, type);
> +
>         return virq;
>  }
>  EXPORT_SYMBOL_GPL(irq_create_fwspec_mapping);
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index 0eebaeef317b..2a429b061171 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -1119,6 +1119,13 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
>         new->irq = irq;
>
>         /*
> +        * If the trigger type is not specified by the caller,
> +        * then use the default for this interrupt.
> +        */
> +       if (!(new->flags & IRQF_TRIGGER_MASK))
> +               new->flags |= irqd_get_trigger_type(&desc->irq_data);
> +
> +       /*
>          * Check whether the interrupt nests into another interrupt
>          * thread.
>          */

This patch looks correct to me. It will have semantic effects though
so we need to be on the lookout for drivers that start to behave strange
as an effect of this, i.e. if they were counting on their .set_type()
to be called during domain setup.

If anyone is aware of such drivers amonst the GPIO chips, please
point them out to me.

Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Yours,
Linus Walleij
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