linux-kernel - Re: [PATCH v7 4/8] dt-bindings: pwm: Support new PWM_STAGGERING

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Message-ID: <20210410140146.5nlp5eczltezbyq2@pengutronix.de>
Date:   Sat, 10 Apr 2021 16:01:46 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Clemens Gruber <clemens.gruber@...ruber.com>,
        linux-pwm@...r.kernel.org, Sven Van Asbroeck <TheSven73@...il.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v7 4/8] dt-bindings: pwm: Support new
 PWM_STAGGERING_ALLOWED flag

Hello Thierry,

On Fri, Apr 09, 2021 at 02:27:34PM +0200, Thierry Reding wrote:
> On Wed, Apr 07, 2021 at 07:33:57AM +0200, Uwe Kleine-König wrote:
> > On Tue, Apr 06, 2021 at 06:41:36PM +0200, Clemens Gruber wrote:
> > > Add the flag and corresponding documentation for the new PWM staggering
> > > mode feature.
> > > 
> > > Cc: Rob Herring <robh+dt@...nel.org>
> > > Signed-off-by: Clemens Gruber <clemens.gruber@...ruber.com>
> > 
> > For the record, I don't like this and still prefer to make this
> > staggering explicit for the consumer by expanding struct pwm_state with
> > an .offset member to shift the active phase in the period.
> 
> How are consumers supposed to know which offset to choose? And worse:
> how should consumers even know that the driver supports phase shifts?

I'm aware that we're a long way from being able to use this. The clean
approach would be to get the offset from the device tree in the same way
as the period. And in the meantime I agree that introducing a flag that
allows to shift the active part in the period is a sane idea. So I
suggest we concentrate on getting the details in the corresponding
discussion straight.

Best regards
Uwe

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

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