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:   Mon, 10 Dec 2018 17:16:25 -0600
From:   Rob Herring <robh@...nel.org>
To:     Vokáč Michal <Michal.Vokac@...ft.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Lukasz Majewski <l.majewski@...ess.pl>,
        Fabio Estevam <fabio.estevam@....com>,
        Lothar Waßmann <LW@...o-electronics.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Vokáč Michal <Michal.Vokac@...ft.com>
Subject: Re: [RFC PATCH v3 1/2] dt-bindings: pwm: imx: Allow switching PWM
 output  between PWM and GPIO

On Thu, 6 Dec 2018 13:41:30 +0000, =?utf-8?B?Vm9rw6HEjSBNaWNoYWw=?= 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.
> 
> Changes in v2:
>  - Do not use the "default" pinctrl state for GPIO.
>  - Use two new "pwm" and "gpio" pinctrl states.
>  - Add a new pwm-gpios signal.
> 
>  Documentation/devicetree/bindings/pwm/imx-pwm.txt | 49 +++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
> 

Reviewed-by: Rob Herring <robh@...nel.org>