linux-kernel - Re: [PATCH V5 2/7] arm64/perf: Update struct arm

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Date:   Wed, 9 Nov 2022 11:30:38 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Anshuman Khandual <anshuman.khandual@....com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, peterz@...radead.org,
        acme@...nel.org, mark.rutland@....com, will@...nel.org,
        catalin.marinas@....com
Cc:     Mark Brown <broonie@...nel.org>, James Clark <james.clark@....com>,
        Rob Herring <robh@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH V5 2/7] arm64/perf: Update struct arm_pmu for BRBE

On 07/11/2022 06:25, Anshuman Khandual wrote:
> Although BRBE is an armv8 speciifc HW feature, abstracting out its various
> function callbacks at the struct arm_pmu level is preferred, as it cleaner
> , easier to follow and maintain.
> 
> Besides some helpers i.e brbe_supported(), brbe_probe() and brbe_reset()
> might not fit seamlessly, when tried to be embedded via existing arm_pmu
> helpers in the armv8 implementation.
> 
> Updates the struct arm_pmu to include all required helpers that will drive
> BRBE functionality for a given PMU implementation. These are the following.
> 
> - brbe_filter	: Convert perf event filters into BRBE HW filters
> - brbe_probe	: Probe BRBE HW and capture its attributes
> - brbe_enable	: Enable BRBE HW with a given config
> - brbe_disable	: Disable BRBE HW
> - brbe_read	: Read BRBE buffer for captured branch records
> - brbe_reset	: Reset BRBE buffer
> - brbe_supported: Whether BRBE is supported or not
> 
> A BRBE driver implementation needs to provide these functionalities.

Could these not be hidden from the generic arm_pmu and kept in the
arm64 pmu backend  ? It looks like they are quite easy to simply
move these to the corresponding hooks in arm64 pmu.

Suzuki