Re: [PATCH 1/2] pwm: sifive: Add DT documentation for SiFive PWM Controller

Uwe Kleine-König
2019-01-15T20:11:49Z

Hello,

this is v3, right? It is helpful to point this out to ease reviewing.

On Fri, Jan 11, 2019 at 01:52:43PM +0530, Yash Shah wrote:
> DT documentation for PWM controller added with updated compatible
> string.

Not sure what was updated here. But assuming this is compared to v2 this
is not a helpful info in the commit log.

> Signed-off-by: Wesley W. Terpstra <wesley@sifive.com>
> [Atish: Compatible string update]
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> Signed-off-by: Yash Shah <yash.shah@sifive.com>
> ---
> .../devicetree/bindings/pwm/pwm-sifive.txt | 37 ++++++++++++++++++++++
> 1 file changed, 37 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/pwm/pwm-sifive.txt
>
> diff --git a/Documentation/devicetree/bindings/pwm/pwm-sifive.txt b/Documentation/devicetree/bindings/pwm/pwm-sifive.txt
> new file mode 100644
> index 0000000..e0fc22a
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/pwm-sifive.txt
> @@ -0,0 +1,37 @@
> +SiFive PWM controller
> +
> +Unlike most other PWM controllers, the SiFive PWM controller currently only
> +supports one period for all channels in the PWM. This is set globally in DTS.
> +The period also has significant restrictions on the values it can achieve,
> +which the driver rounds to the nearest achievable frequency.
> +
> +Required properties:
> +- compatible: Please refer to sifive-blocks-ip-versioning.txt

While the description was too verbose in v2, this is too short. You
should at least mention something like "sifive,pwmX" and
"sifive,$cpuname-pwm" (or how ever that scheme works).

> +- reg: physical base address and length of the controller's registers
> +- clocks: Should contain a clock identifier for the PWM's parent clock.
> +- #pwm-cells: Should be 2.
> + The first cell is the PWM channel number
> + The second cell is the PWM polarity

I'd drop these two lines and refer to bindings/pwm/pwm.txt instead.

> +- sifive,approx-period-ns: the driver will get as close to this period as it can

As already said for v2: I'd drop "approx-".

> +- interrupts: one interrupt per PWM channel
> +
> +PWM RTL that corresponds to the IP block version numbers can be found
> +here:
> +
> +https://github.com/sifive/sifive-blocks/tree/master/src/main/scala/devices/pwm
> +
> +Further information on the format of the IP
> +block-specific version numbers can be found in
> +Documentation/devicetree/bindings/sifive/sifive-blocks-ip-versioning.txt
> +
> +Examples:
> +
> +pwm: pwm@10020000 {
> + compatible = "sifive,fu540-c000-pwm","sifive,pwm0";
> + reg = <0x0 0x10020000 0x0 0x1000>;
> + clocks = <&tlclk>;
> + interrupt-parent = <&plic>;
> + interrupts = <42 43 44 45>;
> + #pwm-cells = <2>;
> + sifive,approx-period-ns = <1000000>;
> +};
> --
> 1.9.1
>
>

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