linux-kernel - RE: [PATCH 1/2] dt-bindings: clock: imx8m: introduce fsl,protected-clocks property

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Date:   Tue, 16 Aug 2022 07:13:27 +0000
From:   Peng Fan <peng.fan@....com>
To:     Sascha Hauer <s.hauer@...gutronix.de>,
        "Peng Fan (OSS)" <peng.fan@....nxp.com>
CC:     "abelvesa@...nel.org" <abelvesa@...nel.org>,
        "abel.vesa@...aro.org" <abel.vesa@...aro.org>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        dl-linux-imx <linux-imx@....com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [PATCH 1/2] dt-bindings: clock: imx8m: introduce
 fsl,protected-clocks property

Hi Sascha,

> Subject: Re: [PATCH 1/2] dt-bindings: clock: imx8m: introduce fsl,protected-
> clocks property
> 
> Hi Peng,
> 
> On Mon, Aug 15, 2022 at 11:36:31AM +0800, Peng Fan (OSS) wrote:
> > From: Peng Fan <peng.fan@....com>
> >
> > i.MX8M Linux run on top of Jailhouse hypervisor, the root cell Linux
> > should not disable clocks used by inmate. This would also benifit AMP
> > to avoid Linux disable clocks used by Cortex-M4/M7.
> >
> > So introduce fsl,protected-clocks for above case.
> >
> > Signed-off-by: Peng Fan <peng.fan@....com>
> > ---
> >  Documentation/devicetree/bindings/clock/imx8m-clock.yaml | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/clock/imx8m-clock.yaml
> > b/Documentation/devicetree/bindings/clock/imx8m-clock.yaml
> > index 458c7645ee68..0ec490ff9a09 100644
> > --- a/Documentation/devicetree/bindings/clock/imx8m-clock.yaml
> > +++ b/Documentation/devicetree/bindings/clock/imx8m-clock.yaml
> > @@ -39,6 +39,10 @@ properties:
> >        ID in its "clocks" phandle cell. See include/dt-bindings/clock/imx8m-
> clock.h
> >        for the full list of i.MX8M clock IDs.
> >
> > +  fsl,protected-clocks:
> > +    description: List of the Protected clock.
> > +    $ref: /schemas/types.yaml#/definitions/uint32-array
> 
> There already is a generic protected-clocks property described in
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithu
> b.com%2Fdevicetree-org%2Fdt-
> schema%2Fblob%2F0d1b78cd0c3d9a3d523ced17d7da64b03f6c18ea%2Fdtsc
> hema%2Fschemas%2Fclock%2Fclock.yaml%23L131&amp;data=05%7C01%7
> Cpeng.fan%40nxp.com%7C5dbc72639c9147765af208da7ec63315%7C686ea
> 1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637961686968811809%7CUn
> known%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI
> 6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=D%2BfJA5h
> wblaX8VH%2BdQoN0pEFmCipfZHHf0ZVo07B4kg%3D&amp;reserved=0
> We probably shouldn't add a property with the same name but different
> meaning.
> 

Thanks for sharing the info. I should check the common bindings before
cook this patchset.

> I am not sure if we want to go the route of a fsl specific property, it looks
> like other SoCs could have similar problems and it might be worth solving
> this problem with a broader view.
> 

I see qcom just drop the clock entries before registering the clocks. But to
i.MX8M, it is not feasible to drop those clocks, unless check the
protected-clocks property before registering every clock. This is odd.

So here I just wanna let i.MX8M clk driver prepare enable the clocks listed
in protected-clocks property to avoid linux disable those clocks.
> Anyway, please add a description to the binding what this property actually
> does.
I will switch to use the common bindings.

Thanks,
Peng.
> 
> Sascha
> 
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