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SubjectRe: [PATCH] arm: bcm2835: Add the PMU to the devicetree.
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On 05/17/2018 12:31 PM, Vince Weaver wrote:
> On Thu, 17 May 2018, Vince Weaver wrote:
>
>> On Thu, 17 May 2018, Peter Zijlstra wrote:
>> with cortex-a7 now, would it be possible to later drop that if proper
>> cortex-a53 support is added to the armv7 pmu driver? Or would that lead
>> to all kinds of back-compatability mess?
>
> For what it's worth, the pi-foundation kernel bcm2710 device tree file
> does:
>
> arm-pmu {
> #ifdef RPI364
> compatible = "arm,armv8-pmuv3", "arm,cortex-a7-pmu";
> #else
> compatible = "arm,cortex-a7-pmu";
> #endif
> interrupt-parent = <&local_intc>;
> interrupts = <9>;
> };
>
>
> Which is probably where I was getting the arm,armv8-pmuv3 from in my
> original patch.

I thought somehow that Marc Z. had unified
arch/arm/kernel/perf_event_v7.c and arch/arm64/kernel/perf_event.c into
a common driver entry point under drivers/perf/arm_pmu.c but I don't see
it and after about 15 minutes looking at it, it does not look as trivial
as I though to separate out those files so the ARMv8 PMU description can
be moved into a generic location for instance.

FWIW, Broadcom STB chips, even when 64-bit capable or often used with an
32-bit ARM kernel, so having the ARMv8 PMUs work under a 32-bit ARM
kernel would be great. The downstream solution we have sued thus far is
to find the closest compatible string to represent those, which is not
great...
--
Florian

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