linux-kernel - Re: [PATCH v5 1/2] pwm: sifive: Add DT documentation for SiFive PWM Controller

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Date:   Wed, 30 Jan 2019 09:14:11 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Yash Shah <yash.shah@...ive.com>
Cc:     palmer@...ive.com, linux-pwm@...r.kernel.org,
        linux-riscv@...ts.infradead.org, thierry.reding@...il.com,
        robh+dt@...nel.org, mark.rutland@....com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        sachin.ghadi@...ive.com, paul.walmsley@...ive.com
Subject: Re: [PATCH v5 1/2] pwm: sifive: Add DT documentation for SiFive PWM
 Controller

On Tue, Jan 29, 2019 at 05:13:18PM +0530, Yash Shah wrote:
> DT documentation for PWM controller added.
> 
> Signed-off-by: Wesley W. Terpstra <wesley@...ive.com>
> [Atish: Compatible string update]
> Signed-off-by: Atish Patra <atish.patra@....com>
> Signed-off-by: Yash Shah <yash.shah@...ive.com>
> ---
>  .../devicetree/bindings/pwm/pwm-sifive.txt         | 33 ++++++++++++++++++++++
>  1 file changed, 33 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..8dcb40d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/pwm-sifive.txt
> @@ -0,0 +1,33 @@
> +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.

You can simply drop this if the first user can set this using the usual
interface. Don't you like this suggestion that I already made a few
times now?

Did you consider to make the driver support only a single output with a
more flexible period setting?

> +The period also has significant restrictions on the values it can achieve,
> +which the driver rounds to the nearest achievable frequency.

Rounding a period to a frequency sounds wrong.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |