linux-kernel - Re: [PATCH v2] add pmu to amlogic meson sm1

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Date:   Tue, 8 Feb 2022 16:02:32 +0000
From:   Benjamin Mordaunt <crawford.benjamin15@...il.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] add pmu to amlogic meson sm1

Okay so this does appear to be behaving with some issues (unless I've
just got 2 of the interrupt numbers wrong, but it seems unlikely at
this stage).

CPUs 0 and 1 seem to be behaving somewhat sensibly, while `perf stat`
reports `<not supported>` for caches and branches with CPUs 2 and 3.
Would this suggest this implementation is indeed broken?

Thanks,
Ben


On Mon, Feb 7, 2022 at 1:47 PM Robin Murphy <robin.murphy@....com> wrote:
>
> On 2022-02-07 13:33, Benjamin Mordaunt wrote:
> > The S905X3’s (Odroid C4) datasheet appears to report 4 individual PMUIRQs,
> > much in the same way as GX. If that is indeed the case, I think this patch
> > applies. Otherwise, is the datasheet wrong if Marc’s comments apply?
>
> A fairly solid test would be to run a sampling event (e.g. `perf stat`)
> taskset to a single CPU and observe the corresponding IRQ count increase
> in /proc/interrupts, for each core in turn. If that behaves as expected
> then chances are everything is indeed sane.
>
> Couple of nitpicks for the patch itself - you're almost there, but
> you've got spurious tabs on the blank lines, plus you need a proper
> commit message and your sign-off above the "---" line - anything you add
> below there is treated as additional commentary for reviewers' benefit
> and will be discarded by `git am`.
>
> Cheers,
> Robin.
>
> >
> > / Ben
> >
> > On Mon, 7 Feb 2022 at 13:20, Robin Murphy <robin.murphy@....com> wrote:
> >
> >> On 2022-02-07 08:14, Neil Armstrong wrote:
> >>> Hi,
> >>>
> >>> On 06/02/2022 15:43, Benjamin Mordaunt wrote:
> >>>> ---
> >>>> The dts for meson sm1 appears to omit the SoC's PMU,
> >>>> which is essential for accessing perf events regarding
> >>>> e.g. cache on e.g. the Odroid C4 platform. Add it.
> >>>>
> >>>>    arch/arm64/boot/dts/amlogic/meson-sm1.dtsi | 13 ++++++++++++-
> >>>>    1 file changed, 12 insertions(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/arch/arm64/boot/dts/amlogic/meson-sm1.dtsi
> >>>> b/arch/arm64/boot/dts/amlogic/meson-sm1.dtsi
> >>>> index 3d8b1f4f2..4147eecd2 100644
> >>>> --- a/arch/arm64/boot/dts/amlogic/meson-sm1.dtsi
> >>>> +++ b/arch/arm64/boot/dts/amlogic/meson-sm1.dtsi
> >>>> @@ -6,6 +6,8 @@
> >>>>    #include "meson-g12-common.dtsi"
> >>>>    #include <dt-bindings/clock/axg-audio-clkc.h>
> >>>> +#include <dt-bindings/interrupt-controller/irq.h>
> >>>> +#include <dt-bindings/interrupt-controller/arm-gic.h>
> >>>>    #include <dt-bindings/power/meson-sm1-power.h>
> >>>>    #include <dt-bindings/reset/amlogic,meson-axg-audio-arb.h>
> >>>>    #include <dt-bindings/reset/amlogic,meson-g12a-audio-reset.h>
> >>>> @@ -90,7 +92,16 @@ l2: l2-cache0 {
> >>>>                compatible = "cache";
> >>>>            };
> >>>>        };
> >>>> -
> >>>> +
> >>>> +    arm-pmu {
> >>>> +        compatible = "arm,cortex-a55-pmu";
> >>>> +        interrupts = <GIC_SPI 137 IRQ_TYPE_LEVEL_HIGH>,
> >>>> +                 <GIC_SPI 138 IRQ_TYPE_LEVEL_HIGH>,
> >>>> +                 <GIC_SPI 153 IRQ_TYPE_LEVEL_HIGH>,
> >>>> +                 <GIC_SPI 154 IRQ_TYPE_LEVEL_HIGH>;
> >>>> +        interrupt-affinity = <&cpu0>, <&cpu1>, <&cpu2>, <&cpu3>;
> >>>> +    };
> >>>> +
> >>>>        cpu_opp_table: opp-table {
> >>>>            compatible = "operating-points-v2";
> >>>>            opp-shared;
> >>>
> >>> Please see Marc's comments about PMU support:
> >>> http://lore.kernel.org/r/8735pcq63o.wl-maz@kernel.org
> >>
> >> If SM1 actually has distinct per-core interrupts as the patch implies
> >> then it's fine - it's only G12B and anything else that combines multiple
> >> PMU IRQs into a single SPI which are unsupportable.
> >>
> >> Robin.
> >>
> >