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

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Message-ID: <a7adf12d-f949-9a95-9c6a-b73017107dc7@arm.com>
Date:   Mon, 7 Feb 2022 13:47:30 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Benjamin Mordaunt <crawford.benjamin15@...il.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

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.
>>
>