Re: [PATCH v4 6/7] gpio: exar: switch to using regmap

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Tue, Nov 10, 2020 at 4:09 PM Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>
> On Tue, Nov 10, 2020 at 05:04:47PM +0200, Andy Shevchenko wrote:
> > On Tue, Nov 10, 2020 at 03:55:51PM +0100, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> > >
> > > We can simplify the code in gpio-exar by using regmap. This allows us to
> > > drop the mutex (regmap provides its own locking) and we can also reuse
> > > regmap's bit operations instead of implementing our own update function.
> >
> > ...
> >
> > > +static const struct regmap_config exar_regmap_config = {
> > > +   .name           = "exar-gpio",
> > > +   .reg_bits       = 16,
> >
> > As per previous version comment.
> >
> > Hold on, the registers are 16-bit wide, but their halves are sparsed!
> > So, I guess 8 and 8 with helpers to get hi and lo parts are essential.
> >
> >
> > TABLE 5: DEVICE CONFIGURATION REGISTERS SHOWN IN BYTE ALIGNMENT
> >
> > > +   .val_bits       = 8,
> > > +};
> >
> > This is basically represents two banks out of 6 8-bit registers each.
>
> ...which makes me wonder if gpio-regmap can be utilized here...
>

But the address width won't affect the actuall accessing of 8 bits
registers in an mmio regmap. Internally the mmio regmap does pretty
much the same thing the previous driver did: call readb()/writeb() on
8-bit "chunks" of the banks.

Bartosz