linux-kernel - Re: [PATCH] gpio: pca953x: Add Maxim MAX7313 PWM support

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Date:   Tue, 15 Oct 2019 17:55:33 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-pwm@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH] gpio: pca953x: Add Maxim MAX7313 PWM support

On Tue, Oct 15, 2019 at 5:30 PM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
>
> Hi Andy,
>
> Thanks for the feedback.
>
> Andy Shevchenko <andy.shevchenko@...il.com> wrote on Mon, 14 Oct 2019
> 20:59:01 +0300:
>
> > On Mon, Oct 14, 2019 at 4:09 PM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> > >
> > > The MAX7313 chip is fully compatible with the PCA9535 on its basic
> > > functions but can also manage the intensity on each of its ports with
> > > PWM. Each output is independent and may be tuned with 16 values (4
> > > bits per output). The period is always 32kHz, only the duty-cycle may
> > > be changed. One can use any output as GPIO or PWM.
> >
> > Can we rather not contaminate driver with this?
> >
> > Just register a separate PWM driver and export its functionality to
> > GPIO, or other way around (in the latter case we actually have PCA8685
> > which provides a GPIO fgunctionality).
> >
>
> I understand your concern but I am not sure to understand which
> solution you have in mind. In the former case, could you explain a bit
> more what you are thinking about? Would linking the PWM support with
> the GPIO driver (code would be located in another .c file) work for
> you? Or maybe you would prefer an MFD on top of the GPIO driver?
>
> As for the later case, I am not willing to re-implement GPIO support in
> an alternate driver for an already supported chip, it is too much work
> for the time I can spend on it.


drivers/pwm/pwm-max7313.c:

probe(platform_device)
{
  struct regmap = pdata;
  ...
}

--- 8< --- 8< ---
drivers/gpio/gpio-pca953x.c:

probe()
{
  struct regmap rm;
...
  if (dev_has_pwm)
   pca953x_register_pwm_driver(rm);
...
}

In the above regmap may be replaced with some (shared) container.

Or other way around. PWM registers GPIO (which actually I prefer since
we have PCA9685 case where PWM provides GPIO functionality, though via
different means)

-- 
With Best Regards,
Andy Shevchenko