Re: [REGRESSION] gpio hogging fails with pinctrl gpio drivers

[Peter Rosin <peda@xxxxxxxxxx>]

On 2020-02-20 09:17, Linus Walleij wrote:
> On Thu, Feb 6, 2020 at 6:33 PM Russell King - ARM Linux admin
> <linux@xxxxxxxxxxxxxxx> wrote:
> 
>> It seems that sometime between 4.20 and 5.5, something has broken the
>> ability to specify gpio-hogs in DT for GPIOs that are written around
>> pinctrl drivers.
> (explanation that makes perfect sense)
>> Consequently, adding a gpio-hog to DT for this driver results in the
>> driver endlessly returning -EPROBE_DEFER.
> 
> I suspect this is sx150x-specific and suspect these two commits:
> 
> 1a1d39e1b8dd pinctrl: sx150x: Register pinctrl before adding the gpiochip
> b930151e5b55 pinctrl: sx150x: Add a static gpio/pinctrl pin range mapping
> 
> I suppose people weren't using hogs very much with the sx150x and
> it didn't turn up in testing so far.
> 
> I don't think for example pinctrl-stmfx.c has this problem, as it registers
> the pin ranges from the device tree as part of the core code.
> But other drivers calling gpiochip_add_pin_range() may be experiencing
> this.
> 
> Peter/Andrey, do you have some idea? Have you tested this usecase (hogs)
> with the sx150x?

I have never created gpio hogs myself, so no, I haven't done any testing
with that. Sorry. I could of course spend some time looking at this, but I
don't know all that much about the wrinkles of the interactions between
pinctrl och gpio. Or plain gpio/pinctrl for that matter. Sure, I extended
this driver, but I haven't really looked at those sub-systems since. I
think others will come up with a solution for this with much less effort
and with less risk of introducing new problems...

Cheers,
Peter