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

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

On Sun, Jun 27, 2021 at 4:13 PM Sergio Paracuellos
<sergio.paracuellos@xxxxxxxxx> wrote:
> On Sun, Jun 27, 2021 at 3:01 PM Andy Shevchenko
> <andy.shevchenko@xxxxxxxxx> wrote:
> > On Sun, Jun 27, 2021 at 1:56 PM Sergio Paracuellos
> > <sergio.paracuellos@xxxxxxxxx> wrote:
> > > On Sun, Jun 27, 2021 at 12:51 PM Andy Shevchenko
> > > <andy.shevchenko@xxxxxxxxx> wrote:
> > > > On Sun, Jun 27, 2021 at 12:47 PM Sergio Paracuellos
> > > > <sergio.paracuellos@xxxxxxxxx> wrote:
> > > > > On Sun, Jun 27, 2021 at 11:33 AM Andy Shevchenko
> > > > > <andy.shevchenko@xxxxxxxxx> wrote:
> > > > > > On Sat, Jun 26, 2021 at 7:18 PM Sergio Paracuellos
> > > > > > <sergio.paracuellos@xxxxxxxxx> 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.

And it can't be split into three children in the overlay?
Let's assume it can't, then the GPIO library function should be
refactored in a way that it takes parameters like base index for the
names and tries to satisfy the caller.

> 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

This should be fixed accordingly.

-- 
With Best Regards,
Andy Shevchenko