Re: [PATCH v2] pinctrl: pinctrl-single: Fix pcs_request_gpio() when bits_per_mux != 0

[David Lechner]

On 02/20/2018 06:56 AM, Andy Shevchenko wrote:
> On Mon, Feb 19, 2018 at 11:57 PM, David Lechner <david@xxxxxxxxxxxxxx> wrote:
> > This fixes pcs_request_gpio() in the pinctrl-single driver when
> > bits_per_mux != 0. It appears this was overlooked when the multiple
> > pins per register feature was added.
> >
> > Fixes: 4e7e8017a80e ("pinctrl: pinctrl-single: enhance to configure multiple pins of different modules")
> > Signed-off-by: David Lechner <david@xxxxxxxxxxxxxx>
> > ---
> >
> > v2 changes:
> > - don't wrap Fixes: line in commit message since it is a special machine-
> >    readable line.
> >
> > There was some discussion in v1 about using DIV_ROUND_UP(), etc. macros, but
> > the consensus was to leave it as-is since it matches existing code and that
> > macros can be introduced in another patch.
> >
> >   drivers/pinctrl/pinctrl-single.c | 22 +++++++++++++++++++---
> >   1 file changed, 19 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pinctrl/pinctrl-single.c b/drivers/pinctrl/pinctrl-single.c
> > index cec7537..a7c5eb3 100644
> > --- a/drivers/pinctrl/pinctrl-single.c
> > +++ b/drivers/pinctrl/pinctrl-single.c
> > @@ -391,9 +391,25 @@ static int pcs_request_gpio(struct pinctrl_dev *pctldev,
> >                          || pin < frange->offset)
> >                          continue;
>
> >                  mux_bytes = pcs->width / BITS_PER_BYTE;
> > -               data = pcs->read(pcs->base + pin * mux_bytes) & ~pcs->fmask;
> > -               data |= frange->gpiofunc;
> > -               pcs->write(data, pcs->base + pin * mux_bytes);
> > +
> > +               if (pcs->bits_per_mux) {
> > +                       int byte_num, offset, pin_shift;
> > +
> > +                       byte_num = (pcs->bits_per_pin * pin) / BITS_PER_BYTE;
> > +                       offset = (byte_num / mux_bytes) * mux_bytes;
> > +                       pin_shift = pin % (pcs->width / pcs->bits_per_pin) *
> > +                                   pcs->bits_per_pin;
> > +
> > +                       data = pcs->read(pcs->base + offset);
> > +                       data &= ~(pcs->fmask << pin_shift);
> > +                       data |= frange->gpiofunc << pin_shift;
> > +                       pcs->write(data, pcs->base + offset);
> > +               } else {
>
> > +                       data = pcs->read(pcs->base + pin * mux_bytes);
> > +                       data &= ~pcs->fmask;
> > +                       data |= frange->gpiofunc;
> > +                       pcs->write(data, pcs->base + pin * mux_bytes);
>
> Just an idea, you may leave this almost untouched and do calculate
> pin_shift and offset in condition, like
>
> if (...) {
>   pin_shift = ...
>   offset = ...
> } else {
>   pin_shift = 0;
>   offset = pin * mux_bytes;
> }
>
>                         data = pcs->read(pcs->base + offset);
>                         data &= ~(pcs->fmask << pin_shift);
>                         data |= frange->gpiofunc << pin_shift;
>                         pcs->write(data, pcs->base + offset);
>
> It's also possible to split to two changes, where first introduces
> that variables and their default values (see 'else' branch) and second
> one introduces an if branch override.
>
> > +               }
> >                  break;

Yes, there are many ways this could be done. However, I would like
to just leave it as it is since it matches the patterns used
elsewhere in this file.