Re: [PATCH v4 1/2] gpio: Add support for IDT 79RC3243x GPIO controller

[Michael Walle]

Am 2021-04-28 17:02, schrieb Andy Shevchenko:
> On Wed, Apr 28, 2021 at 5:48 PM Michael Walle <michael@xxxxxxxx> wrote:
> > [Adding Mark here, too]
> >
> > Am 2021-04-28 16:32, schrieb Andy Shevchenko:
> > > On Wed, Apr 28, 2021 at 5:04 PM Michael Walle <michael@xxxxxxxx> wrote:
> > >> Am 2021-04-28 15:44, schrieb Andy Shevchenko:
> > >> > On Wed, Apr 28, 2021 at 2:57 PM Michael Walle <michael@xxxxxxxx> wrote:
> > >> >>
> > >> >> Am 2021-04-28 13:07, schrieb Andy Shevchenko:
> > >> >> > On Wed, Apr 28, 2021 at 1:51 AM Michael Walle <michael@xxxxxxxx> wrote:
> > >> >> >> Am 2021-04-26 12:29, schrieb Andy Shevchenko:
> > >> >> >> > On Mon, Apr 26, 2021 at 12:55 PM Thomas Bogendoerfer
> > >> >> >> > <tsbogend@xxxxxxxxxxxxxxxx> wrote:
> > >> >> >> >
> > >> >> >> > 2) there is gpio-regmap generic code, that may be worth
> > >> >> >> > considering.
> > >> >> >>
> > >> >> >> This driver uses memory mapped registers. While that is
> > >> >> >> also possible with gpio-regmap, there is one drawback:
> > >> >> >> it assumes gpiochip->can_sleep = true for now, see [1].
> > >> >> >> Unfortunately, there is no easy way to ask the regmap
> > >> >> >> if its mmio/fastio.
> > >> >> >
> > >> >> > I don't see how it is an impediment.
> > >> >>
> > >> >> You'd have to use the *_cansleep() variants with the gpios,
> > >> >> which cannot be used everywhere, no?
> > >> >
> > >> > *can* sleep means that it requires a sleeping context to run, if your
> > >> > controller is fine with that, there are no worries. OTOH if you want
> > >> > to run this in an atomic context, then consumers can't do with that
> > >> > kind of controller.
> > >>
> > >> Ok, then we are on the same track.
> > >>
> > >> > What I meant above (and you stripped it here) is
> > >> > to add a patch that will fix that and set it based on
> > >> > gpio_regmap_config.
> > >>
> > >> Yes, but ideally, it would ask the regmap. Otherwise that
> > >> information is redundant and might mismatch, i.e. gpio_regmap_config
> > >> tell can_sleep=false but the regmap is an I2C type for example. Also
> > >> if a driver wants to support both regmap types, we are no step
> > >> further.
> > >
> > > Yeah, I agree that is a band aid, but you are free to fix it actually
> > > on regmap level.
> > > I don't think it will require an enormous amount of work there.
> >
> > I'd love to fix that, but Mark was against exposing that property
> > outside of regmap. So it it what it is for now ;) Maybe he'll change
> > his mind or someone has another idea.
>
> Then let's go to ugly variant with duplicating it in gpio-regmap
> config. with a FIXME note or so. I don't think we should allow new
> drivers be based on bgpio_init().

Agreed, given that a possible fix should be easy enough later.

-michael