Re: [PATCH 2/2] dt-bindings: mfd: syscon: Add support for regmap fast-io
From: Krzysztof Kozlowski
Date: Sat Apr 02 2022 - 07:38:56 EST
On 01/04/2022 15:50, AngeloGioacchino Del Regno wrote:
> The syscon driver now enables the .fast_io regmap configuration when
> the 'fast-io' property is found in a syscon node.
> Keeping in mind that, in regmap, fast_io is checked only if we are
> not using hardware spinlocks, allow the fast-io property only if
> there is no hwlocks reference (and vice-versa).
I have doubts you need a property for this. "fast" is subjective in
terms of hardware, so this looks more like a software property, not
I think most of MMIOs inside a SoC are considered fast. Usually also the
syscon/regmap consumer knows which regmap it gets, so knows that it is
fast or not.
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> Documentation/devicetree/bindings/mfd/syscon.yaml | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
> diff --git a/Documentation/devicetree/bindings/mfd/syscon.yaml b/Documentation/devicetree/bindings/mfd/syscon.yaml
> index 13baa452cc9d..85a2e83b5861 100644
> --- a/Documentation/devicetree/bindings/mfd/syscon.yaml
> +++ b/Documentation/devicetree/bindings/mfd/syscon.yaml
> @@ -83,11 +83,26 @@ properties:
> $ref: /schemas/types.yaml#/definitions/uint32
> enum: [1, 2, 4, 8]
> + fast-io:
> + description:
> + Indicates that this bus has a very fast IO, for which
> + acquiring a mutex would be significant overhead.
> + When present, regmap will use a spinlock instead.
Regmap is current implementation behind this, but it's not related to
hardware, so how about removing it from the description? Something like:
"..., for which different locking methods should be used to reduce
overhead (e.g. spinlock instead of mutex)."
> + type: boolean
> maxItems: 1
> Reference to a phandle of a hardware spinlock provider node.
> + required:
> + - hwlocks
> + not:
> + required:
> + - fast-io
> - compatible
> - reg