linux-kernel - RE: [EXT] Re: [PATCH 1/3] dt-bindings: perf: fsl-imx-ddr: Add i.MX95 compatible

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Message-ID: <DB7PR04MB514668A8B172CD1A2187BC408C84A@DB7PR04MB5146.eurprd04.prod.outlook.com>
Date:   Wed, 6 Dec 2023 01:42:51 +0000
From:   Xu Yang <xu.yang_2@....com>
To:     Conor Dooley <conor@...nel.org>
CC:     Frank Li <frank.li@....com>, "will@...nel.org" <will@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
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        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
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Subject: RE: [EXT] Re: [PATCH 1/3] dt-bindings: perf: fsl-imx-ddr: Add i.MX95
 compatible

Hi Hi Conor,

> 
> On Fri, Dec 01, 2023 at 06:41:59AM +0000, Xu Yang wrote:
> > Hi Conor,
> >
> > >
> > > On Mon, Nov 27, 2023 at 03:32:06PM +0800, Xu Yang wrote:
> > > > i.MX95 has a more precise counting capability than i.MX93. This will add
> > > > a compatible for it.
> > >
> > > It is hard to tell from this comment, but I figure this "more precise
> > > capability" is not an option you can enable, but instead makes the
> > > programming model of this device different to that of the imx93?
> >
> > Actually, imx95 is compatible with imx93 except AXI ID filter capability.
> > But for AXI ID filter, imx95 is using different registers and bits from
> > imx93 for filter configuration.
> 
> This sounds like it conflicts with...
> 
> > To distinguish them, I need use different
> > compatible because programming model cannot recognize which device is
> > running.
> >
> > compatible = "fsl,imx95-ddr-pmu";
> 
> > compatible = "fsl,imx95-ddr-pmu", "fsl,imx93-ddr-pmu";
> 
> ...this. If drivers for the imx93 need changes to work on the imx95,
> then `compatible = "fsl,imx95-ddr-pmu", "fsl,imx93-ddr-pmu";` cannot be
> used. If they will work, with only the new imx95 features being
> non-functional, then you can use it.

Yes, it is. When compatible = "fsl,imx95-ddr-pmu", "fsl,imx93-ddr-pmu" is used,
only the new imx95 features is not functional, other basic function works for
both imx95 and imx93.

Thanks,
Xu Yang

> 
> > Both above compatible is okay for me. Therefore, "fsl,imx95-ddr-pmu" is needed.