linux-kernel - Re: [RFC PATCH v1 15/20] pwm: Add capability for PWM Driver managed state

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Message-ID: <CACRpkdYZpQqYPYLaMrqQxOzvaU2DqaxWOwhfq4=2EK6hMP8oHQ@mail.gmail.com>
Date:   Fri, 17 Sep 2021 00:00:05 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     "D, Lakshmi Sowjanya" <lakshmi.sowjanya.d@...el.com>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Lee Jones <lee.jones@...aro.org>,
        "open list:PWM SUBSYSTEM" <linux-pwm@...r.kernel.org>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Mark Gross <mgross@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Saha, Tamal" <tamal.saha@...el.com>, bala.senthil@...el.com
Subject: Re: [RFC PATCH v1 15/20] pwm: Add capability for PWM Driver managed state

On Tue, Aug 24, 2021 at 6:48 PM <lakshmi.sowjanya.d@...el.com> wrote:

> From: Christopher Hall <christopher.s.hall@...el.com>
>
> Add additional flag that can be set by drivers to indicate that the
> driver will manage its own PWM state. When calling pwm_ops.apply the
> driver applies the requested state change to the pwm_device reconciling,
> if possible, any conflicting requests.
>
> Intel(R) Timed I/O devices support very limited PWM capabilities. The
> duty cycle must always be 50% of the period. When changing one parameter
> at a time through the sysfs interface, it isn't possible for the user or
> the PWM subsystem to maintain this relation.
>
> Signed-off-by: Christopher Hall <christopher.s.hall@...el.com>
> Signed-off-by: Tamal Saha <tamal.saha@...el.com>
> Signed-off-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@...el.com>
> Reviewed-by: Mark Gross <mgross@...ux.intel.com>

These PWM changes clearly need to be reviewed by the PWM
subsystem maintainers, and I think all of the output generation
portions of this really need to go into the PWM subsystem.

Yours,
Linus Walleij