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

[Robin Murphy]

On 2022-02-08 16:02, Benjamin Mordaunt wrote:
> 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?

Taking a closer look, the interrupts for CPUs 2 and 3 here are clearly 
wrong since they already belong to some audio controllers in the DTSI. I 
looked up documentation and found an S905D3 manual from Khadas which 
documents SPI 137 (GIC interrupt 169) as "|PMUIRQ_a[3:0]", which I can't 
read as anything other than "logical OR of all 4 PMU IRQs". Not sure 
about SPI 138 but I'd guess it's something that just happens to fire in 
a manner that appears to sort of work for the PMU.

Sadly it looks like Neil's instinct was right and this one is also in 
fact dead, sorry :(

Robin.

> Thanks,
> Ben
>
>
> On Mon, Feb 7, 2022 at 1:47 PM Robin Murphy <robin.murphy@xxxxxxx> 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@xxxxxxx> 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@xxxxxxxxxx
> > > >
> > > > 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.