linux-kernel - Re: [PATCH v2] gpio: mt7621: support gpio-line-names property

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Message-ID: <CAMhs-H-WwCfPDspgxzN=W8QouZ7WPAeyJDYf_6=YezyCkTM=Vw@mail.gmail.com>
Date:   Sun, 27 Jun 2021 12:56:15 +0200
From:   Sergio Paracuellos <sergio.paracuellos@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        John Thomson <git@...nthomson.fastmail.com.au>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        NeilBrown <neil@...wn.name>,
        René van Dorst <opensource@...rst.com>,
        Nicholas Mc Guire <hofrat@...dl.org>
Subject: Re: [PATCH v2] gpio: mt7621: support gpio-line-names property

On Sun, Jun 27, 2021 at 12:51 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Sun, Jun 27, 2021 at 12:47 PM Sergio Paracuellos
> <sergio.paracuellos@...il.com> wrote:
> > On Sun, Jun 27, 2021 at 11:33 AM Andy Shevchenko
> > <andy.shevchenko@...il.com> wrote:
> > >
> > > On Sat, Jun 26, 2021 at 7:18 PM Sergio Paracuellos
> > > <sergio.paracuellos@...il.com> wrote:
> > > >
> > > > The default handling of the gpio-line-names property by the
> > > > gpiolib-of implementation does not work with the multiple
> > > > gpiochip banks per device structure used by the gpio-mt7621
> > > > driver.
> > > >
> > > > This commit adds driver level support for the device tree
> > > > property so that GPIO lines can be assigned friendly names.
>
> > > > This driver has three gpiochips with 32 gpios each. Core implementation
> > >
> > > implementation
> > >
> > >
> > > > got gpio's repeated along each gpio chip if chip.names is not assigned.
> > > > To avoid this behaviour driver will set this names as empty or
> > >
> > > the driver
> > > these names
> > >
> > > > with desired friendly line names. Consider the following sample with
> > > > minimal entries for the first chip with this patch changes applied:
> > >
> > > The same comment as per v1:
> > >
> > > Any idea why it's not a duplicate of
> > > https://elixir.bootlin.com/linux/v5.13-rc7/C/ident/devprop_gpiochip_set_names,
> > > and why the latter is not called in your case?
> >
> > The core properly calls this function but not in the way expected.
> > This driver implements three banks of 32 gpios each internally using
> > one gpiochip per bank, all of them in the same device. So the core
> > code you are pointing out here duplicates the same names along the
> > three gpiochips which is not the expected behaviour. So implementing
> > in this way and setting names at least reserved avoids the core code
> > to be run and also avoids the duplication getting expected behaviour
> > for all the banks and each line friendly name.
>
> Isn't it the problem of how we supply fwnode in that case?
> Another possibility is to fix DT (although I'm not sure it's now possible).

Since the fwnode is the same for all banks of the same device, each bank
repeats the first MTK_BANK_WIDTH label names in each bank.

This commit populates the gc.names member of each bank from the
device-tree node within the driver. This overrides the default behavior
since devprop_gpiochip_set_names() will only be called if names is NULL.

Best regards,
    Sergio Paracuellos

>
> Have you considered the above?
>
> --
> With Best Regards,
> Andy Shevchenko