linux-kernel - Re: [PATCH V1 RESEND 1/3] perf/imx_ddr: Add system PMU identifier for userspace

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Message-ID: <CAL_JsqJU7JjFXSU8m5hyMyXd7L8F33_wHc+tETWXj9NBt9NV8g@mail.gmail.com>
Date:   Wed, 20 May 2020 09:10:12 -0600
From:   Rob Herring <robh@...nel.org>
To:     Joakim Zhang <qiangqing.zhang@....com>
Cc:     "john.garry@...wei.com" <john.garry@...wei.com>,
        "will@...nel.org" <will@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        dl-linux-imx <linux-imx@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V1 RESEND 1/3] perf/imx_ddr: Add system PMU identifier for userspace

On Tue, May 19, 2020 at 8:56 PM Joakim Zhang <qiangqing.zhang@....com> wrote:
>
>
> > -----Original Message-----
> > From: Rob Herring <robh@...nel.org>
> > Sent: 2020年5月20日 2:51
> > To: Joakim Zhang <qiangqing.zhang@....com>
> > Cc: john.garry@...wei.com; will@...nel.org; mark.rutland@....com;
> > shawnguo@...nel.org; dl-linux-imx <linux-imx@....com>;
> > linux-arm-kernel@...ts.infradead.org; devicetree@...r.kernel.org;
> > linux-kernel@...r.kernel.org
> > Subject: Re: [PATCH V1 RESEND 1/3] perf/imx_ddr: Add system PMU identifier
> > for userspace
> >
> > On Tue, May 12, 2020 at 03:31:13PM +0800, Joakim Zhang wrote:
> > > The DDR Perf for i.MX8 is a system PMU whose axi id would different
> > > from SoC to SoC. Need expose system PMU identifier for userspace which
> > > refer to /sys/bus/event_source/devices/<PMU DEVICE>/identifier.
> >
> > Why not just expose the AXI ID if that's what's different?
>
> Hi Rob,
>
> Each master has their own AXI ID, such as USB, GPU, VPU etc, it is various from different SoCs. We want to add system PMU support in perf tool, so we want to expose something from perf driver to identify each SoC.
> When we know which SoC it is, we can get each master AXI ID. If this patch can be accepted, /sys/bus/event_source/devices/<PMU DEVICE>/identifier could be a common interface for all system PMUs.
>
> I will change to add a property to identify SoC, to see if it is better. Thanks.

Isn't that what you have already with this patch? My point is you can
already read /proc/device-tree/compatible, read the PMU compatible, or
have an SoC device which exposes SoC info.

Rob