Re: [PATCH v1 1/6] dt-bindings: cache: Document the sifive,perfmon-counters property

Krzysztof Kozlowski
2024-02-18T18:35:39Z

On 18/02/2024 16:29, Samuel Holland wrote:
> Hi Krzysztof,
>
> On 2024-02-17 3:00 AM, Krzysztof Kozlowski wrote:
>> On 16/02/2024 01:08, Samuel Holland wrote:
>>> The SiFive Composable Cache controller contains an optional PMU with a
>>> configurable number of event counters. Document a property which
>>
>> Configurable in what context? By chip designers or by OS? Why this
>> cannot be deduced from the compatible?
>
> This parameter is configurable by the chip designers.
>
> The information certainly can be deduced from the SoC-specific compatible
> string, but doing so makes the driver only work on that specific list of SoCs.

Usually that's exactly what's expected, so why here usual approach is wrong?

> When provided via a property, the driver can work without changes on any SoC
> that uses this IP block. (None of the SoCs currently listed in the binding

Sorry, properties are not a work-around for missing compatibles.

> contain a PMU, so there is no backward compatibility concern with adding the new
> property.)
>
> My understanding of the purpose of the SoC-specific compatible string is to
> handle eventualities (silicon bugs, integration quirks, etc.), not to
> intentionally limit the driver to a narrow list of hardware.

Depends what is the hardware. For most of licensed blocks, the final
design is the hardware so equals to its compatible.

Best regards,
Krzysztof