linux-kernel - Re: [PATCH 4/7] dt-bindings: timestamp: Add Tegra234 support

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Date:   Mon, 7 Nov 2022 14:06:00 -0600
From:   Rob Herring <robh@...nel.org>
To:     Dipen Patel <dipenp@...dia.com>
Cc:     thierry.reding@...il.com, jonathanh@...dia.com,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-gpio@...r.kernel.org, linus.walleij@...aro.org,
        devicetree@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH 4/7] dt-bindings: timestamp: Add Tegra234 support

On Thu, Nov 03, 2022 at 10:45:20AM -0700, Dipen Patel wrote:
> Added timestamp provider support for the Tegra234 in devicetree
> bindings.
> 
> Signed-off-by: Dipen Patel <dipenp@...dia.com>
> ---
>  .../timestamp/nvidia,tegra194-hte.yaml        | 44 +++++++++++++++++--
>  1 file changed, 40 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/timestamp/nvidia,tegra194-hte.yaml b/Documentation/devicetree/bindings/timestamp/nvidia,tegra194-hte.yaml
> index c31e207d1652..158dbe58c49f 100644
> --- a/Documentation/devicetree/bindings/timestamp/nvidia,tegra194-hte.yaml
> +++ b/Documentation/devicetree/bindings/timestamp/nvidia,tegra194-hte.yaml
> @@ -4,7 +4,7 @@
>  $id: http://devicetree.org/schemas/timestamp/nvidia,tegra194-hte.yaml#
>  $schema: http://devicetree.org/meta-schemas/core.yaml#
>  
> -title: Tegra194 on chip generic hardware timestamping engine (HTE)
> +title: Tegra on chip generic hardware timestamping engine (HTE) provider
>  
>  maintainers:
>    - Dipen Patel <dipenp@...dia.com>
> @@ -23,6 +23,8 @@ properties:
>      enum:
>        - nvidia,tegra194-gte-aon
>        - nvidia,tegra194-gte-lic
> +      - nvidia,tegra234-gte-aon
> +      - nvidia,tegra234-gte-lic

How is the h/w in this chip different from the existing one? I'm 
assuming it must be because you don't have a fallback compatible.

>  
>    reg:
>      maxItems: 1
> @@ -43,9 +45,8 @@ properties:
>      description:
>        HTE lines are arranged in 32 bit slice where each bit represents different
>        line/signal that it can enable/configure for the timestamp. It is u32
> -      property and depends on the HTE instance in the chip. The value 3 is for
> -      GPIO GTE and 11 for IRQ GTE.
> -    enum: [3, 11]
> +      property and the value depends on the HTE instance in the chip.

If this statement was true, then this property makes sense...

> +    enum: [3, 11, 17]
>  
>    '#timestamp-cells':
>      description:
> @@ -55,6 +56,41 @@ properties:
>        mentioned in the nvidia GPIO device tree binding document.
>      const: 1
>  
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - nvidia,tegra194-gte-aon
> +              - nvidia,tegra234-gte-aon
> +    then:
> +      properties:
> +        nvidia,slices:
> +          const: 3
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - nvidia,tegra194-gte-lic
> +    then:
> +      properties:
> +        nvidia,slices:
> +          const: 11
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - nvidia,tegra234-gte-lic
> +    then:
> +      properties:
> +        nvidia,slices:
> +          const: 17

However, if there is only one possible value for each compatible, then 
being per instance can't really be true. I guess 'aon' or 'lic' define 
the instance? That's not normal practice. Are there other differences?

It seems like 'nvidia,slices' should be implied from the compatible 
string.

Rob