linux-kernel - Re: [PATCH 0/2] perf: ARM CoreSight PMU support

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Message-ID: <2f3000b9-6c31-7ef7-46c2-6b7a42fe893b@hisilicon.com>
Date:   Mon, 9 May 2022 20:20:30 +0800
From:   Shaokun Zhang <zhangshaokun@...ilicon.com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        Will Deacon <will@...nel.org>,
        Besar Wicaksono <bwicaksono@...dia.com>
CC:     <catalin.marinas@....com>, <mark.rutland@....com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <sudeep.holla@....com>, <thanu.rangarajan@....com>,
        <Michael.Williams@....com>, <treding@...dia.com>,
        <jonathanh@...dia.com>, <vsethi@...dia.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [PATCH 0/2] perf: ARM CoreSight PMU support

Hi,

On 2022/5/9 18:02, Suzuki K Poulose wrote:
> Cc: Mike Williams, Mathieu Poirier
> 
> On 09/05/2022 10:28, Will Deacon wrote:
>> On Sun, May 08, 2022 at 07:28:08PM -0500, Besar Wicaksono wrote:
>>> Add driver support for ARM CoreSight PMU device and event attributes for NVIDIA
>>> implementation. The code is based on ARM Coresight PMU architecture and ACPI ARM
>>> Performance Monitoring Unit table (APMT) specification below:
>>>   * ARM Coresight PMU:
>>>          https://developer.arm.com/documentation/ihi0091/latest
>>>   * APMT: https://developer.arm.com/documentation/den0117/latest
>>>
>>> Notes:
>>>   * There is a concern on the naming of the PMU device.
>>>     Currently the driver is probing "arm-coresight-pmu" device, however the APMT
>>>     spec supports different kinds of CoreSight PMU based implementation. So it is
>>>     open for discussion if the name can stay or a "generic" name is required.
>>>     Please see the following thread:
>>>     http://lists.infradead.org/pipermail/linux-arm-kernel/2022-May/740485.html
>>>
>>> Besar Wicaksono (2):
>>>    perf: coresight_pmu: Add support for ARM CoreSight PMU driver
>>>    perf: coresight_pmu: Add support for NVIDIA SCF and MCF attribute
>>>
>>>   arch/arm64/configs/defconfig                  |    1 +
>>>   drivers/perf/Kconfig                          |    2 +
>>>   drivers/perf/Makefile                         |    1 +
>>>   drivers/perf/coresight_pmu/Kconfig            |   10 +
>>>   drivers/perf/coresight_pmu/Makefile           |    7 +
>>>   .../perf/coresight_pmu/arm_coresight_pmu.c    | 1317 +++++++++++++++++
>>>   .../perf/coresight_pmu/arm_coresight_pmu.h    |  147 ++
>>>   .../coresight_pmu/arm_coresight_pmu_nvidia.c  |  300 ++++
>>>   .../coresight_pmu/arm_coresight_pmu_nvidia.h  |   17 +
>>>   9 files changed, 1802 insertions(+)
>>
>> How does this interact with all the stuff we have under
>> drivers/hwtracing/coresight/?
> 
> Absolutely zero, except for the name. The standard
> is named "CoreSight PMU" which is a bit unfortunate,
> given the only link, AFAIU, with the "CoreSight" architecture
> is the Lock Access Register(LAR). For reference, the
> drivers/hwtracing/coresight/ is purely "CoreSight" self-hosted
> tracing and the PMU is called "cs_etm" (expands to coresight etm).
> Otherwise the standard doesn't have anything to do with what
> exists already in the kernel.
> 
> That said, I am concerned that the "coresight_pmu" is easily confused
> with what exists today. Given that this is more of a "PMU" standard
> for the IPs in the Arm world, it would be better to name it as such
> avoiding any confusion with the existing PMUs.
> 
> One potential recommendation for the name is, "Arm PMU"  (The ACPI table is named Arm PMU Table).
> But then that could be clashing with the armv8_pmu :-(.
> 
> Some of the other options are :
> 
> "Arm Generic PMU"
> "Arm Uncore PMU"

To be honest, if wants to distinguish from Arm core PMU, the "Uncore PMU" is a
better choice just in my opinion. The x86 including Intel and AMD also do the
uncore PMU driver and with "uncore_" prefix.

Thanks,
Shaokun

> "Arm PMU"
> 
> Suzuki
> 
>>
>> Will
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> .

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