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From:   Rob Herring <robh@kernel.org>
Date:   Wed, 20 May 2020 09:10:12 -0600
Message-ID: <CAL_JsqJU7JjFXSU8m5hyMyXd7L8F33_wHc+tETWXj9NBt9NV8g@mail.gmail.com>
Subject: Re: [PATCH V1 RESEND 1/3] perf/imx_ddr: Add system PMU identifier for userspace
To:     Joakim Zhang <qiangqing.zhang@nxp.com>
Cc:     "john.garry@huawei.com" <john.garry@huawei.com>,
        "will@kernel.org" <will@kernel.org>,
        "mark.rutland@arm.com" <mark.rutland@arm.com>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Tue, May 19, 2020 at 8:56 PM Joakim Zhang <qiangqing.zhang@nxp.com> wrot=
e:
>
>
> > -----Original Message-----
> > From: Rob Herring <robh@kernel.org>
> > Sent: 2020=E5=B9=B45=E6=9C=8820=E6=97=A5 2:51
> > To: Joakim Zhang <qiangqing.zhang@nxp.com>
> > Cc: john.garry@huawei.com; will@kernel.org; mark.rutland@arm.com;
> > shawnguo@kernel.org; dl-linux-imx <linux-imx@nxp.com>;
> > linux-arm-kernel@lists.infradead.org; devicetree@vger.kernel.org;
> > linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH V1 RESEND 1/3] perf/imx_ddr: Add system PMU identif=
ier
> > 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 whic=
h
> > > 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 variou=
s from different SoCs. We want to add system PMU support in perf tool, so w=
e 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 patc=
h can be accepted, /sys/bus/event_source/devices/<PMU DEVICE>/identifier co=
uld 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