On Mon, Jun 05, 2023 at 04:01:48PM +0200, Mike Looijmans wrote:
> Add bindings for a fixed-rate clock that retrieves its rate from an
> NVMEM provider. This allows to store clock settings in EEPROM or EFUSE
> or similar device.
>
> Component shortages lead to boards being shipped with different clock
> crystals, based on what was available at the time. The clock frequency
> was written to EEPROM at production time. Systems can adapt to a wide
> range of input frequencies using the clock framework, but this required
> us to patch the devicetree at runtime or use some custom driver. This
> provides a more generic solution.
>
> Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
>
> ---
>
> Changes in v4:
> Use proper "if" block and add example dts
>
> Changes in v3:
> Modify fixed-clock instead of introducing nvmem-clock
>
> Changes in v2:
> Changed "fixed-clock" into "nvmem-clock" in dts example
> Add minItems:1 to nvmem-cell-names
>
> .../bindings/clock/fixed-clock.yaml | 42 ++++++++++++++++++-
> 1 file changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/clock/fixed-clock.yaml b/Documentation/devicetree/bindings/clock/fixed-clock.yaml
> index b0a4fb8256e2..71a5791da438 100644
> --- a/Documentation/devicetree/bindings/clock/fixed-clock.yaml
> +++ b/Documentation/devicetree/bindings/clock/fixed-clock.yaml
> @@ -12,7 +12,9 @@ maintainers:
>
> properties:
> compatible:
> - const: fixed-clock
> + enum:
> + - fixed-clock
> + - fixed-clock-nvmem
>
> "#clock-cells":
> const: 0
> @@ -26,11 +28,41 @@ properties:
> clock-output-names:
> maxItems: 1
>
> + nvmem-cells:
> + minItems: 1
> + maxItems: 2
> + description:
> + Reads clock-frequency and/or clock-accuracy from an NVMEM provider in
> + binary native integer format. The size of the NVMEM cell can be 1, 2, 4
> + or 8 bytes. If the contents of the nvmem are all zeroes or all 0xff, the
> + value reverts to the one given in the property.
> +
> + nvmem-cell-names:
> + minItems: 1
> + items:
> + - const: clock-frequency
> + - const: clock-accuracy
> +
> required:
> - compatible
> - "#clock-cells"
> - clock-frequency
>
> +allOf:
> + - if:
> + properties:
> + compatible:
> + contains:
> + const: fixed-clock-nvmem
> + then:
> + required:
> + - nvmem-cells
> + - nvmem-cell-names
> + else:
> + properties:
> + nvmem-cells: false
> + nvmem-cell-names: false
> +
> additionalProperties: false
>
> examples:
> @@ -41,4 +73,12 @@ examples:
> clock-frequency = <1000000000>;
> clock-accuracy = <100>;
> };
> + - |
> + clock {
> + compatible = "fixed-clock-nvmem";
> + #clock-cells = <0>;
> + clock-frequency = <48000000>;
If the freq comes from nvmem, why is this needed?
I think this should probably be a separate schema file as the only
other thing shared is #clock-cells.
Rob
