Re: [PATCH v5 2/3] gpio: loongson: add gpio driver support

[Yinbo Zhu]

在 2022/12/13 下午5:36, Linus Walleij 写道:
> On Mon, Dec 12, 2022 at 9:13 AM Yinbo Zhu <zhuyinbo@xxxxxxxxxxx> wrote:
>
> > mask_irq/unmask_irq/irq_ack/ function always be called by
> > handle_level_irq/handle_edge_irq in current irq domain. and the
> > handle_level_irq/handle_edge_irq will be called  by handle_irq_desc that
> > ask know which irq is.
> >
> > when a peripheral need to use a gpio irq that gpio irq driver need know
> > irq status and call irq desc->irq_handler.
> >
> > so I don't got it about which case it is unnecessary to know which irq.
>
> Sorry I don't understand what you are asking, can you elaborate?
>
> Do you mean that you don't know which driver will not call ->to_irq()
> on the gpiochip? That would be any driver that takes an IRQ directly in
> the device tree:
>
> gpio: gpio {
>      interrupt-controller;
>      #interrupt-cells = <2>;
>      ....
> };
>
> device {
>      interrupts = <&gpio 14 IRQ_TYPE_LEVEL_HIGH>;
>      ....
> };
>
> This case will only call the irqchip callbacks and will never call
> the .to_irq() on the gpio_chip.

I mean that if the current domain is a valid doamin, every interrupt 
must have an interrupt status.

If there is no interrupt status, no one can cover the interrupt,
and no one will call 14 irq's desc->handle_irq (handle_level_irq)
and Loongson-2 gpio doesn't have irq status register, so Loongson-2
gpio irqchip shouldn't be implemented.
> > > You find an example of a hierarchical GPIO irqchip using the
> > > GPIOLIB_IRQCHIP in drivers/gpio/gpio-ixp4xx.c.
> >
> > Loongson-2 gpio irq hardware only a enable register, and when a gpio irq
> > happen, then will has a such flow:  "cpuintc -> liointc -> gpioinc ->
> > generic_handle_domain_irq -> handle_level_irq ->
> > peripheral-action(action->handler)"
> >
> > generic_handle_domain_irq need rely on specific hwirq that ask gpio irq
> > hardware has a status register but Loongson-2 gpio irq hardware doesn't
> > have it.
> >
> > so I still think it wasn't appropriate that for loongson-2 gpio driver
> > add a irq chip.
>
> generic_handle_domain_irq() is of no concern, what matters is if
> your interrupt is hierarchical or not, the callback in the GPIO chip
> can be a simple remapping of the numberspace followed by
> a call to the parent callbacks.
>
> Yours,
> Linus Walleij
Hi

I think gpio irq domain should be a normal irq domain that like other 
irq domain. that need a function A to call virq desc handler in gpio irq 
domain.  if no use generic_handler_domain_irq or similar interface,
that will no one to call irq_desc->irq_handler.

"cpuintc -> liointc -> gpioinc -> generic_handle_domain_irq ->
handle_level_irq -> peripheral-action(action->handler)"
>