Re: [PATCH v1 12/16] pinctrl: starfive: Add pinctrl driver for StarFive SoCs

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

On Wed, Oct 13, 2021 at 6:58 PM Andy Shevchenko
<andy.shevchenko@xxxxxxxxx> wrote:
> On Wed, Oct 13, 2021 at 06:38:14PM +0200, Emil Renner Berthing wrote:
> > On Tue, 12 Oct 2021 at 19:03, Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote:
> > > On Tue, Oct 12, 2021 at 4:43 PM Emil Renner Berthing <kernel@xxxxxxxx> wrote:

> > > > +               v = pinmux[i];
> > > > +               dout = ((v & BIT(7)) << (31 - 7)) | ((v >> 24) & 0xffU);
> > > > +               doen = ((v & BIT(6)) << (31 - 6)) | ((v >> 16) & 0xffU);
> > > > +               din  = (v >> 8) & 0xffU;
> > >
> > > What is this voodoo for?
> >
> > In order to do pinmux we need the following pieces of information from
> > the device tree for each pin ("GPIO" they call it):
> >
> > output signal: 0-133 + 1bit reverse flag
> > output enable signal: 0-133 + 1bit reverse flag
> > optional input signal: 0-74 + special "none" value, right now 0xff
> > gpio number: 0-63
> >
> > As the code is now all that info is packed into a u32 for each pin
> > using the GPIOMUX macro defined in the dt-binding header added in
> > patch 10. There is also a diagram for how this packing is done. The
> > above voodoo is for unpacking that.
> >
> > I'd very much like to hear if you have a better solution for how to
> > convey that information from the device tree to here.
>
> At very least this code should have something like above in the comment.

And perhaps introduce some helper macros to access the fields?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds