linux-kernel - Re: [RFC PATCH v3 1/2] dt-bindings: pwm: imx: Allow switching PWM output between PWM and GPIO

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Date:   Fri, 14 Dec 2018 14:45:18 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Michal.Vokac@...ft.com
Cc:     "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, linux-pwm@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        l.majewski@...ess.pl, Fabio Estevam <fabio.estevam@....com>,
        Lothar Waßmann <LW@...o-electronics.de>
Subject: Re: [RFC PATCH v3 1/2] dt-bindings: pwm: imx: Allow switching PWM
 output between PWM and GPIO

On Thu, Dec 6, 2018 at 2:41 PM Vokáč Michal <Michal.Vokac@...ft.com> wrote:

> Output of the PWM block on i.MX SoCs is always low when the block is
> disabled. This can cause issues when inverted PWM polarity is needed.
> With inverted polarity a duty cycle = 0% corresponds to high level on
> the output. Now, when PWM is disabled its output instantly goes low
> which corresponds to duty cycle = 100%.
>
> To get a truly inverted PWM output two pinctrl states of the PWM pin
> can be used. Configure the pin to GPIO function when PWM is disabled
> and switch back to PWM function whenever non-zero duty cycle is needed.
>
> Signed-off-by: Michal Vokáč <michal.vokac@...ft.com>
> ---
> Changes in v3:
>  - Slightly different description of the pinctrl and pwm-gpio.

This looks good to me.

Acked-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij