linux-kernel - Re: [PATCH v4 5/6] arm64: dts: cix: add initial CIX P1(SKY1) dts support

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Message-ID: <Z91AG0lH1JNN7NHq@nchen-desktop>
Date: Fri, 21 Mar 2025 18:31:55 +0800
From: Peter Chen <peter.chen@...tech.com>
To: Marc Zyngier <maz@...nel.org>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	catalin.marinas@....com, will@...nel.org, arnd@...db.de,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, cix-kernel-upstream@...tech.com,
	marcin@...zkiewicz.com.pl,
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	Fugang Duan <fugang.duan@...tech.com>
Subject: Re: [PATCH v4 5/6] arm64: dts: cix: add initial CIX P1(SKY1) dts
 support

On 25-03-21 09:04:00, Marc Zyngier wrote:
> > On 25-03-20 09:36:37, Marc Zyngier wrote:
> > > Peter Chen <peter.chen@...tech.com> wrote:
> > > >
> > > > +     pmu-a520 {
> > > > +             compatible = "arm,cortex-a520-pmu";
> > > > +             interrupts = <GIC_PPI 7 IRQ_TYPE_LEVEL_LOW &ppi_partition0>;
> > > > +     };
> > > > +
> > > > +     pmu-a720 {
> > > > +             compatible = "arm,cortex-a720-pmu";
> > > > +             interrupts = <GIC_PPI 7 IRQ_TYPE_LEVEL_LOW &ppi_partition1>;
> > > > +     };
> > > > +
> > > > +     pmu-spe {
> > > > +             compatible = "arm,statistical-profiling-extension-v1";
> > > > +             interrupts = <GIC_PPI 5 IRQ_TYPE_LEVEL_LOW 0>;
> > > > +     };
> > >
> > > SPE should follow the same model as the PMU, as each CPU has its own
> > > SPE implementation, exposing different micro-architectural details.
> > >
> >
> > Hi Marc,
> >
> > Thanks for your reply. But there is only one compatible string
> > "statistical-profiling-extension-v1" at drivers/perf/arm_spe_pmu.c,
> > how could differentiate pmu-spe-a720 and pmu-spe-a520, do I need
> > to change arm_spe_pmu.c as well?
> 
> I don't think there is a need to have different compatible. The driver
> can probe which CPU this is on, and work out the implemented
> subfeatures from the PMSIDR_EL1 register. New compatible strings are
> better avoided when there is a way to probe/discover the HW (and in
> most cases, there is).
> 
> Note that this equally applies to TRBE, which also explicitly deals
> with interrupt partitioning and yet only has a single compatible.
> Please consider adding TRBE support when you repost this series.
> 

Hi Marc,

Thanks for your comment, we need to discuss it internally. Since it
is very initial dts support for CIX sky1 SoC, I will delete pmu-spe
support at this time, and add better support for it when adding
more components next time.

-- 

Best regards,
Peter