linux-kernel - Re: [PATCH] arm64: dts: renesas: r9a07g044: Add Cortex-A55 PMU node

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Date:   Mon, 30 Jan 2023 14:30:04 +0000
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Will Deacon <will.deacon@....com>,
        Biju Das <biju.das.jz@...renesas.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH] arm64: dts: renesas: r9a07g044: Add Cortex-A55 PMU node

Hi Mark,

On Mon, Jan 30, 2023 at 2:10 PM Mark Rutland <mark.rutland@....com> wrote:
>
> On Mon, Jan 30, 2023 at 02:04:44PM +0000, Lad, Prabhakar wrote:
> > Hi Mark and Will,
> >
> > On Fri, Jan 27, 2023 at 9:48 PM Biju Das <biju.das.jz@...renesas.com> wrote:
> > >
> > > Hi Prabhakar,
> > >
> > >
> > > > Subject: Re: [PATCH] arm64: dts: renesas: r9a07g044: Add Cortex-A55 PMU node
> > > >
> > > > Hi Biju,
> > > >
> > > > Thank you for the review.
> > > >
> > > > On Fri, Jan 27, 2023 at 6:38 PM Biju Das <biju.das.jz@...renesas.com> wrote:
> > > > >
> > > > > Hi Prabhakar,
> > > > >
> > > > > Thanks for the patch.
> > > > >
> > > > > > Subject: [PATCH] arm64: dts: renesas: r9a07g044: Add Cortex-A55 PMU
> > > > > > node
> > > > > >
> > > > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > > > >
> > > > > > Enable the performance monitor unit for the Cortex-A55 cores on the
> > > > > > RZ/G2L
> > > > > > (r9a07g044) SoC.
> > > > > >
> > > > > > Signed-off-by: Lad Prabhakar
> > > > > > <prabhakar.mahadev-lad.rj@...renesas.com>
> > > > > > ---
> > > > > >  arch/arm64/boot/dts/renesas/r9a07g044.dtsi | 5 +++++
> > > > > >  1 file changed, 5 insertions(+)
> > > > > >
> > > > > > diff --git a/arch/arm64/boot/dts/renesas/r9a07g044.dtsi
> > > > > > b/arch/arm64/boot/dts/renesas/r9a07g044.dtsi
> > > > > > index 80b2332798d9..ff9bdc03a3ed 100644
> > > > > > --- a/arch/arm64/boot/dts/renesas/r9a07g044.dtsi
> > > > > > +++ b/arch/arm64/boot/dts/renesas/r9a07g044.dtsi
> > > > > > @@ -161,6 +161,11 @@ opp-50000000 {
> > > > > >               };
> > > > > >       };
> > > > > >
> > > > > > +     pmu_a55 {
> > > > > > +             compatible = "arm,cortex-a55-pmu";
> > > > > > +             interrupts-extended = <&gic GIC_PPI 7
> > > > > > + IRQ_TYPE_LEVEL_HIGH>;
> > > > >
> > > > > Just a question, Is it tested?
> > > > Yes this was tested with perf test
> > > >
> > > > > timer node[1] defines irq type as LOW, here it is high.
> > > > You are right looking at the RZG2L_InterruptMapping_rev01.xlsx this should
> > > > be LOW. (I followed the SPI IRQS where all the LEVEL interrupts are HIGH)
> > > >
> > > > > Also do we need to define (GIC_CPU_MASK_SIMPLE(2) | IRQ_TYPE_LEVEL_LOW) as
> > > > it has 2 cores??
> > > > >
> > > > No this is not required for example here [0] where it has 6 cores.
> > >
> > > I may be wrong, That is the only example[1], where the A55 PMU per cpu interrupts and number of a55 cores in the DT
> > > are not matching.
> > >
> > Some SoCs specify the GIC_CPU_MASK_SIMPLE(x) while describing the PPI
> > interrupt for the PMU and some dont [1]. What should be the correct
> > usage when specifying the PPI interrupts for the PMU with multiple CPU
> > cores (we are using
> > arm,cortex-a55-pmu)?
> >
> >  [1] https://elixir.bootlin.com/linux/latest/B/ident/arm%2Ccortex-a55-pmu
>
> This is a GICv3 system. the GICv3 interrupts binding *does not* have a cpumask,
> and it's always wrong to use GIC_CPU_MASK_SIMPLE() (or any mask, for that
> matter) for GICv3
>
> The GICv2 binding has the mask, but even there it's arguably pointless.
>
> Please do not add the mask here, since it would violate the GICv3 binding.
>
Thank you for the clarification.

(Note to myself, to drop GIC_CPU_MASK_SIMPLE() from timer nodes from
rzg2l family)

Cheers,
Prabhakar