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

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Message-ID: <CAMhs-H9gw63j98vVo3y0ymW4_6rFNL8u5cYNM2hzyrmkPB3h3w@mail.gmail.com>
Date:   Sun, 27 Jun 2021 15:12:50 +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

Hi Andy,

On Sun, Jun 27, 2021 at 3:01 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Sun, Jun 27, 2021 at 1:56 PM Sergio Paracuellos
> <sergio.paracuellos@...il.com> wrote:
> > 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.
>
> Can you point out the DT in question?

https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git/tree/drivers/staging/mt7621-dts/mt7621.dtsi?h=staging-next

Gpio node:

 gpio: gpio@600 {
              #gpio-cells = <2>;
              #interrupt-cells = <2>;
              compatible = "mediatek,mt7621-gpio";
              gpio-controller;
              gpio-ranges = <&pinctrl 0 0 95>;
              interrupt-controller;
              reg = <0x600 0x100>;
              interrupt-parent = <&gic>;
              interrupts = <GIC_SHARED 12 IRQ_TYPE_LEVEL_HIGH>;
   };

My overlay:

&gpio {
    gpio-line-names = "", "", "", "",
                      "", "", "SFP LOS", "extcon port5 PoE compat",
                      "SFP module def0", "LED blue SFP", "SFP tx disable", "",
                      "switch USB power", "mode", "", "buzzer",
                      "LED blue pwr", "switch port5 PoE out", "reset";
};



>
> > 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.
>
> I believe this commit is not needed in the proposed (i.e. duplication) shape.
> The fwnode supports primary and secondary ones. Thus, we may create a
> pair of fwnodes when they will unify properties per device with
> properties per child together (child is primary and device, i.e.
> parent, is secondary).

There are no child nodes, all the stuff is in the same parent node
and, as I said, belongs to the same device but internally uses three
gpiochips. This case is pretty much the same as the following already
added commit for gpio-brcmstb:

https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git/commit/drivers/gpio/gpio-brcmstb.c?id=5eefcaed501dd9e3933dbff58720244bd75ed90f

Best regards,
    Sergio Paracuellos
>
> --
> With Best Regards,
> Andy Shevchenko