Re: [RFC PATCH 7/7] irqchip/apple-aic: add SMP support to the Apple AIC driver.

[Arnd Bergmann]

On Thu, Jan 21, 2021 at 1:50 PM Mohamed Mediouni
<mohamed.mediouni@xxxxxxxxxxxx> wrote:
> > On 21 Jan 2021, at 13:44, Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
> >> @@ -186,8 +325,11 @@ static int __init apple_aic_init(struct device_node *node,
> >>       if (WARN(!aic.base, "unable to map aic registers\n"))
> >>               return -EINVAL;
> >>
> >> +       aic.fast_ipi = of_property_read_bool(node, "fast-ipi");
> >
> > Where is this property documented, and what decides which one to use?
> It’s getting documented in the next patch set.
>
> This property is there to enable support for older iPhone processors
> later on, some of which do not have fast IPI support.
>
> On Apple M1, fast-ipi is always on.

Ok, makes sense. Does fast-ipi mean you cannot use the other mode at
all, or is it just faster as implied by the name? If so, how much faster?

       Arnd