Re: [Xen-devel] [PATCH 4/6] xen/arm: platforms: Add Tegra platform to support basic IRQ routing

[Julien Grall <julien.grall@xxxxxxx>]

Hi Chris,

On 07/07/17 19:08, Chris Patterson wrote:
> On Fri, Jul 7, 2017 at 12:25 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
> > Hi Chris,
> >
> >
> > On 06/07/17 23:00, Chris Patterson wrote:
> > > > > The purpose of tegra_interrupt_compat is to maintain a tegra-specific
> > > > > whitelist of interrupt controllers we know how to route.  Presumably,
> > > > > there may be custom boards out there that may have additional
> > > > > interrupt routing capabilities that this patch set would not support
> > > > > as-is.  I'm not sure of an appropriate way to maintain that logic and
> > > > > merge them.  However, I am certainly open to suggestion, if you have
> > > > > any ideas.
> > > >
> > > >
> > > > Those custom boards would likely have a different machine compatible
> > > > string
> > > > because the SOC would be different. So I think the tegra_interrupt_compat
> > > > is
> > > > not necessary.
> > > Sorry about the delayed response...
> > >
> > > This check effectively filters out GPIO controllers.  Any GPIO-sourced
> > > interrupts route through the GPIO controller's interrupt, and need not
> > > apply for map_irq_to_domain().  Devices requiring GPIO-based
> > > interrupts would need to be passed through with the associated
> > > controller (or maybe virtualize the GPIO routing?).
> >
> > I am a bit confused. Could you give a concrete example based on tegra
> > platform?
> I'm thinking of devices where interrupt-parent is &gpio (as opposed to
> &lic or &gic). Here is an example on tegra-smaug:
>
> wifi: wifi_bcm4354 {
>     compatible = "bcm,bcm4354";
>     interrupt-parent = <&gpio>;
>     interrupts = <TEGRA_GPIO(H, 2) IRQ_TYPE_LEVEL_HIGH>;
>     wl_reg_on = <&gpio TEGRA_GPIO(H, 1) GPIO_ACTIVE_HIGH>;
>     wl_host_wake = <&gpio TEGRA_GPIO(H, 2) IRQ_TYPE_LEVEL_HIGH>;
>     nvidia,pmc-wakeup = <&pmc
>     PMC_WAKE_TYPE_EVENT 8 PMC_TRIGGER_TYPE_HIGH>;
> };
Hmmm, you are right here. What confuse me is the comment on the top of 
tegra_irq_is_routable:
/*
 * Returns true iff the given IRQ is routable -- that is, if it i descended
 * from the platform's primary GIC.
 */

In both GPIO and LIC, the final interrupt will be coming from the GIC.
However, the later seems to have a direct translation with the GIC, 
hence why they are routable. Right?
If so I would update the comment to make it clear.

Cheers,

--
Julien Grall

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