Re: [PATCH 3/6] dt-bindings: mips: brcm: Document mips-cbr-reg property

Conor Dooley
2024-05-03T22:14:15Z

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On Fri, May 03, 2024 at 09:33:35PM +0200, Christian Marangi wrote:
> On Fri, May 03, 2024 at 05:21:41PM +0100, Conor Dooley wrote:
> > On Fri, May 03, 2024 at 03:54:03PM +0200, Christian Marangi wrote:
> > > Document mips-cbr-reg and mips-broken-cbr-reg property.
> > >
> > > Some SoC suffer from a BUG where read_c0_brcm_cbr() might return 0
> > > if called from TP1. The CBR address is always the same on the SoC
> > > hence it can be provided in DT to handle broken case where bootloader
> > > doesn't init it or SMP where read_c0_brcm_cbr() returns 0 from TP1.
> > >
> > > Usage of this property is to give an address also in these broken
> > > configuration/bootloader.
> > >
> > > If the SoC/Bootloader ALWAYS provide a broken CBR address the property
> > > "mips-broken-cbr-reg" can be used to ignore any value already set in the
> > > registers for CBR address.
> > >
> > > Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
> > > ---
> > > .../devicetree/bindings/mips/brcm/soc.yaml | 32 +++++++++++++++++++
> > > 1 file changed, 32 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/mips/brcm/soc.yaml b/Documentation/devicetree/bindings/mips/brcm/soc.yaml
> > > index 975945ca2888..12d394b7e011 100644
> > > --- a/Documentation/devicetree/bindings/mips/brcm/soc.yaml
> > > +++ b/Documentation/devicetree/bindings/mips/brcm/soc.yaml
> > > @@ -55,6 +55,21 @@ properties:
> > > under the "cpus" node.
> > > $ref: /schemas/types.yaml#/definitions/uint32
> > >
> > > + mips-broken-cbr-reg:
> > > + description: Declare that the Bootloader init a broken
> > > + CBR address in the registers and the one provided from
> > > + DT should always be used.
> >
> > Why is this property even needed, is it not sufficient to just add the
> > mips-cbr-reg property to the DT for SoCs that need it and use the
> > property when present?
> >
>
> I described this in the cover letter.

It needs to be described in /this patch/. Cover letters usually don't
end up in the commit history and I din't read them while looking for the
justification for a change :)

> CBR might be set by the Bootloader
> and might be not 0. In that case the value is ignored as an extra
> precaution and the broken propetry is needed.

I dunno, if the bootloader is bad, you need to set a property anyway,
so why not set mips-cbr-reg?

> > > + type: boolean
> > > +
> > > + mips-cbr-reg:
> >
> > Missing a vendor prefix.
> >
>
> I will change this to bmips,cbr-reg hope it's O.K.
>
> > > + description: Reference address of the CBR.
> > > + Some SoC suffer from a BUG where read_c0_brcm_cbr() might
> > > + return 0 if called from TP1. The CBR address is always the
> > > + same on the SoC hence it can be provided in DT to handle
> > > + broken case where bootloader doesn't init it or SMP where
> >
> > s/init/initialise/ please :)
> >
>
> Sure!
>
> > Thanks,
> > Conor.
> >
> > > + read_c0_brcm_cbr() returns 0 from TP1.
> > > + $ref: /schemas/types.yaml#/definitions/uint32
> > > +
> > > patternProperties:
> > > "^cpu@[0-9]$":
> > > type: object
> > > @@ -64,6 +79,23 @@ properties:
> > > required:
> > > - mips-hpt-frequency
> > >
> > > +dependencies:
> > > + mips-broken-cbr-reg: [ mips-cbr-reg ]
> > > +
> > > +if:
> > > + properties:
> > > + compatible:
> > > + contains:
> > > + anyOf:
> > > + - const: brcm,bcm6358
> > > + - const: brcm,bcm6368
> > > +
> > > +then:
> > > + properties:
> > > + cpus:
> > > + required:
> > > + - mips-cbr-reg
> > > +
> > > additionalProperties: true
> > >
> > > examples:
> > > --
> > > 2.43.0
> > >
>
>
>
> --
> Ansuel

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