linux-kernel - Re: [PATCH v2] dt-bindings: opp: operating-points-v2-ti-cpu: Describe opp-supported-hw

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Message-ID: <20240909142910.GA4188780-robh@kernel.org>
Date: Mon, 9 Sep 2024 09:29:10 -0500
From: Rob Herring <robh@...nel.org>
To: Dhruva Gole <d-gole@...com>
Cc: Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
	Stephen Boyd <sboyd@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Vignesh Raghavendra <vigneshr@...com>, linux-pm@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] dt-bindings: opp: operating-points-v2-ti-cpu:
 Describe opp-supported-hw

On Thu, Sep 05, 2024 at 10:44:32AM +0530, Dhruva Gole wrote:
> It seems like we missed migrating the complete information from the old
> DT binding where we had described what the opp-supported-hw is supposed
> to describe. Hence, bring back the description from the previous binding
> to the current one along with a bit more context on what the values are
> supposed to be.
> 
> Fixes: e576a9a8603f ("dt-bindings: cpufreq: Convert ti-cpufreq to json schema")
> Signed-off-by: Dhruva Gole <d-gole@...com>
> ---
> Changes in v2:
> - Drop the patch where I updated Maintainers since it's already picked
>   by Viresh.
> - Add more details of how to populate the property based on device
>   documents like TRM/ datasheet.
> - Link to v1: https://lore.kernel.org/r/20240903-b4-opp-dt-binding-fix-v1-0-f7e186456d9f@ti.com
> ---
>  .../bindings/opp/operating-points-v2-ti-cpu.yaml         | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/opp/operating-points-v2-ti-cpu.yaml b/Documentation/devicetree/bindings/opp/operating-points-v2-ti-cpu.yaml
> index 02d1d2c17129..fd260b20c59c 100644
> --- a/Documentation/devicetree/bindings/opp/operating-points-v2-ti-cpu.yaml
> +++ b/Documentation/devicetree/bindings/opp/operating-points-v2-ti-cpu.yaml
> @@ -45,7 +45,21 @@ patternProperties:
>        clock-latency-ns: true
>        opp-hz: true
>        opp-microvolt: true
> -      opp-supported-hw: true
> +      opp-supported-hw:
> +        description: |
> +          Two bitfields indicating:
> +            1. Which revision of the SoC the OPP is supported by.
> +            This can be easily obtained from the datasheet of the
> +            part being ordered/used. For eg. it will be 0x01 for SR1.0
> +            2. Which eFuse bits indicate this OPP is available.
> +            The device datasheet has a table talking about Device Speed Grades.
> +            If one were to sort this table and only retain the unique elements
> +            of the MAXIMUM OPERATING FREQUENCY starting from the first row
> +            which tells the lowest OPP, to the highest. The corresponding bits
> +            need to be set based on N elements of speed grade the device supports.
> +            So, if there are 3 possible unique MAXIMUM OPERATING FREQUENCY
> +            in the table, then BIT(0), (1) and (2) will be set, which means
> +            the value shall be 0x7.

I still have no clue what the bitfield layout is. Where do 0x1 and 0x7 
go in the examples from above?

How many 32-bit words is not defined by the common 
schema. You need to define that here (maxItems/minItems).

Rob