linux-kernel - Re: [PATCH v2 3/5] dt-bindings: mips: brcm: Document brcm,bmips-cbr-reg property

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Date: Tue, 7 May 2024 08:07:28 -0500
From: Rob Herring <robh@...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>,
	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>,
	Álvaro Fernández Rojas <noltari@...il.com>,
	linux-mips@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Daniel González Cabanelas <dgcbueu@...il.com>
Subject: Re: [PATCH v2 3/5] dt-bindings: mips: brcm: Document
 brcm,bmips-cbr-reg property

On Fri, May 03, 2024 at 11:20:59PM +0200, Christian Marangi wrote:
> Document brcm,bmips-cbr-reg and brcm,bmips-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
> "brcm,bmips-broken-cbr-reg" can be used to ignore any value already set
> in the registers for CBR address.

Why can't these be implied from an SoC specific compatible?

It's not a great design where you have to update the DT which should be 
provided from the bootloader in order to work-around bootloader 
issues...

> 
> Signed-off-by: Christian Marangi <ansuelsmth@...il.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..29af8f0db785 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
>  
> +      brcm,bmips-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 wouldn't brcm,bmips-cbr-reg being present indicate to use it?

> +        type: boolean
> +
> +      brcm,bmips-cbr-reg:
> +        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 initialise it or SMP
> +          where read_c0_brcm_cbr() returns 0 from TP1.
> +        $ref: /schemas/types.yaml#/definitions/uint32

CBR is never defined anywhere in this patch. 

> +
>      patternProperties:
>        "^cpu@[0-9]$":
>          type: object
> @@ -64,6 +79,23 @@ properties:
>      required:
>        - mips-hpt-frequency
>  
> +dependencies:
> +  brcm,bmips-broken-cbr-reg: [ brcm,bmips-cbr-reg ]

The inline syntax (i.e. []) means you need quotes for commas.

This has no effect because you are applying it to the root node. Needs 
to be a the same level as the properties.

> +
> +if:
> +  properties:
> +    compatible:
> +      contains:
> +        anyOf:
> +          - const: brcm,bcm6358
> +          - const: brcm,bcm6368

Replace anyOf+const with enum.

> +
> +then:
> +  properties:
> +    cpus:
> +      required:
> +        - brcm,bmips-cbr-reg
> +
>  additionalProperties: true
>  
>  examples:
> -- 
> 2.43.0
>