Re: [PATCH] of/irq: Add a quirk for controllers with their own definition of interrupt-map

["Lad, Prabhakar" <prabhakar.csengg@gmail.com>]

On Mon, Nov 29, 2021 at 6:33 PM Rob Herring <robh@kernel.org> wrote:
>
> On Mon, Nov 29, 2021 at 6:13 AM Lad, Prabhakar
> <prabhakar.csengg@gmail.com> wrote:
> >
>
> I timed my vacation well...
>
> > On Mon, Nov 29, 2021 at 10:34 AM Marc Zyngier <maz@kernel.org> wrote:
> > >
> > > On Sat, 27 Nov 2021 00:42:49 +0000,
> > > Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com> wrote:
> > > >
> > > > Hi Marc,
> > > >
> > > > > -----Original Message-----
> > > > > From: Marc Zyngier <maz@kernel.org>
> > > > > Sent: 23 November 2021 09:11
> > > > > To: Geert Uytterhoeven <geert@linux-m68k.org>
> > > > > Cc: linux-kernel@vger.kernel.org; devicetree@vger.kernel.org; kernel-team@android.com; Rob Herring
> > > > > <robh@kernel.org>; John Crispin <john@phrozen.org>; Biwen Li <biwen.li@nxp.com>; Chris Brandt
> > > > > <Chris.Brandt@renesas.com>; linux-renesas-soc@vger.kernel.org; Prabhakar Mahadev Lad
> > > > > <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > > > Subject: Re: [PATCH] of/irq: Add a quirk for controllers with their own definition of interrupt-map
> > > > >
> > > > > On Tue, 23 Nov 2021 08:44:19 +0000,
> > > > > Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > > > >
> > > > > > Hi Marc,
> > > > > >
> > > > > > On Tue, Nov 23, 2021 at 9:33 AM Marc Zyngier <maz@kernel.org> wrote:
> > > > > > > On Tue, 23 Nov 2021 07:57:48 +0000,
> > > > > > > Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > > > > > > Summarized:
> > > > > > > >   - Before the bad commit, and after your fix, irqc-rza1 is invoked,
> > > > > > > >     and the number of interrupts seen is correct, but input events
> > > > > > > >     are doubled.
> > > > > > > >   - After the bad commit, irqc-rza1 is not invoked, and there is an
> > > > > > > >     interrupt storm, but input events are OK.
> > > > > > >
> > > > > > > OK, that's reassuring, even if the "twice the events" stuff isn't
> > > > > > > what you'd expect. We at least know this is a separate issue, and
> > > > > > > that this patch on top of -rc1 brings you back to the 5.15 behaviour.
> > > > > > >
> > > > > > > I'd expect it to be the case for the other platforms as well.
> > > > > >
> > > > > > OK.
> > > > > >
> > > > > > BTW, what would have been the correct way to do this for irqc-rza1?
> > > > > > I think we're about to make the same mistake with RZ/G2L IRQC
> > > > > > support[1]?
> > > > >
> > > > > Indeed, and I was about to look into it.
> > > > >
> > > > > There are multiple ways to skin this cat, including renaming 'interrupt-map' to 'my-own-private-
> > > > > interrupt-map'. Or use something akin the new 'msi-range' (which we could call interrupt-range), and
> > > > > replace:
> > > > >
> > > > >   interrupt-map = <0 0 &gic GIC_SPI 4 IRQ_TYPE_LEVEL_HIGH>,
> > > > >                   <1 0 &gic GIC_SPI 5 IRQ_TYPE_LEVEL_HIGH>,
> > > > >                   <2 0 &gic GIC_SPI 6 IRQ_TYPE_LEVEL_HIGH>,
> > > > >                   <3 0 &gic GIC_SPI 7 IRQ_TYPE_LEVEL_HIGH>,
> > > > >                   <4 0 &gic GIC_SPI 8 IRQ_TYPE_LEVEL_HIGH>,
> > > > >                   <5 0 &gic GIC_SPI 9 IRQ_TYPE_LEVEL_HIGH>,
> > > > >                   <6 0 &gic GIC_SPI 10 IRQ_TYPE_LEVEL_HIGH>,
> > > > >                   <7 0 &gic GIC_SPI 11 IRQ_TYPE_LEVEL_HIGH>;
> > > > >
> > > > > with:
> > > > >
> > > > >   interrupt-range = <&gic GIC_SPI 4 IRQ_TYPE_LEVEL_HIGH 0 8>;
>
> interrupts would work just fine here:
>
> interrupts = <GIC_SPI 4 IRQ_TYPE_LEVEL_HIGH>,
>   <GIC_SPI 5 IRQ_TYPE_LEVEL_HIGH>,
>   <GIC_SPI 6 IRQ_TYPE_LEVEL_HIGH>,
>   <GIC_SPI 7 IRQ_TYPE_LEVEL_HIGH>,
>   <GIC_SPI 8 IRQ_TYPE_LEVEL_HIGH>,
>   <GIC_SPI 9 IRQ_TYPE_LEVEL_HIGH>,
>   <GIC_SPI 10 IRQ_TYPE_LEVEL_HIGH>,
>   <GIC_SPI 11 IRQ_TYPE_LEVEL_HIGH>;
>
> We don't need a different solution for N:1 interrupts from N:M. Sure,
> that could become unweldy if there are a lot of interrupts (just like
> interrupt-map), but is that an immediate problem?
>
It's just that with this approach the driver will have to index the
interrupts instead of reading from DT.

Marc - is it OK with the above approach?

> > > > >
> > > > Just to clarify, do you suggest to add interrupt-range as a generic
> > > > DT property or SoC/company specific property?
> > >
> > > As a generic one. I have no interest in SoC-specific stuff (though you
> > > are free to invent your own and run it by Rob).
> > >
> > OK will go with a generic one.
> >
> > > > If you meant to add generic property where would you suggest to
> > > > document this property?
> > >
> > > Ideally collocated with the rest of the interrupt properties.
> > >
> > OK, I will go with interrupts.txt for now. Is that OK with you Rob?
>
> Nope. As the rest of interrupts are documented in DT Spec it goes
> there and there needs to be a schema (in dtschema).
>
Agreed.

> > (the reason I ask because interrupt-map/mask haven't been documented).
>
> Yes, they are. Only for the last 20+ years.
>
My bad I was referring in
Documentation/devicetree/bindings/interrupt-controller/

Cheers,
Prabhakar

> Rob