linux-kernel - Re: [PATCH v3 2/4] dt-bindings: mips: brcm: Document brcm,bmips-cbr-reg property

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Date: Wed, 8 May 2024 18:14:34 +0100
From: Conor Dooley <conor@...nel.org>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: Hauke Mehrtens <hauke@...ke-m.de>,
	Rafał Miłecki <zajec5@...il.com>,
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	linux-mips@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/4] dt-bindings: mips: brcm: Document
 brcm,bmips-cbr-reg property

On Wed, May 08, 2024 at 07:07:18PM +0200, Christian Marangi wrote:
> Document brcm,bmips-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.
> 
> Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
> ---
>  .../devicetree/bindings/mips/brcm/soc.yaml    | 23 +++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mips/brcm/soc.yaml b/Documentation/devicetree/bindings/mips/brcm/soc.yaml
> index 975945ca2888..77f73ab48c11 100644
> --- a/Documentation/devicetree/bindings/mips/brcm/soc.yaml
> +++ b/Documentation/devicetree/bindings/mips/brcm/soc.yaml
> @@ -55,6 +55,15 @@ properties:
>           under the "cpus" node.
>          $ref: /schemas/types.yaml#/definitions/uint32
>  
> +      brcm,bmips-cbr-reg:
> +        description: Reference address of the CBR.

Pretty sure that Rob commented last time that there's no definition
anywhere here of CBR, but I don't see either a response to him or an
explanation in v3 as to what CBR means.

> +          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 initialise it or SMP
> +          where read_c0_brcm_cbr() returns 0 from TP1.

Why is a ?linux? function name in the binding? Surely this is just
"or in SMP systems where reading CBR returns 0 from...", no? Ditto
above.

Thanks,
Conor.

> +        $ref: /schemas/types.yaml#/definitions/uint32
> +
>      patternProperties:
>        "^cpu@[0-9]$":
>          type: object
> @@ -64,6 +73,20 @@ properties:
>      required:
>        - mips-hpt-frequency
>  
> +if:
> +  properties:
> +    compatible:
> +      contains:
> +        enum:
> +          - brcm,bcm6358
> +          - brcm,bcm6368
> +
> +then:
> +  properties:
> +    cpus:
> +      required:
> +        - brcm,bmips-cbr-reg
> +
>  additionalProperties: true
>  
>  examples:
> -- 
> 2.43.0
> 

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