Re: Can't pinctrl-baytrail be a module?

[Jean Delvare <jdelvare@suse.de>]

On Fri, 12 Feb 2016 13:59:45 +0100, Takashi Iwai wrote:
> On Thu, 11 Feb 2016 14:44:28 +0100,
> Mathias Nyman wrote:
> > 
> > On 11.02.2016 15:08, Takashi Iwai wrote:
> > > On Thu, 11 Feb 2016 13:56:45 +0100,
> > > Mika Westerberg wrote:
> > >>
> > >> +Jean and Mathias
> > >>
> > >> On Thu, Feb 11, 2016 at 01:45:16PM +0100, Takashi Iwai wrote:
> > >>> Hi,
> > >>>
> > >>> while discussing whether to enable pinctrl drivers on openSUSE distro
> > >>> kernels, I wonder why pinctrl-baytrail is built-in only.  Basically
> > >>> the forced built-in is the only reason against the enablement in
> > >>> distro kernels.
> > >>>
> > >>> The other Intel pinctrl drivers seem to be tristate.
> > >>> Any missing piece there?
> > >>
> > >> Jean sent a patch against this couple of hours ago.
> > >
> > > I noticed it right after I send my mail, too, sorry :)
> > >
> > >> I explained to him
> > >> that there is some ACPI GPIO magic happening on Baytrail-T based
> > >> machines such as Asus T100 where the GPIO driver is needed early at
> > >> boot, or something along those lines. I've CC'd Mathias Nyman the
> > >> original author who hopefully remembers this better.
> > >
> > > I know of pinctrl-cherryview is needed before others like shdci, but
> > > for Baytrail-T, it's more than that?
> > >
> > 
> > If I remember correctly the reason was that the gpio driver was supposed
> > to work with Hardware reduced ACPI events (in ACPI 5).
> > Basically ACPI telling operating system it wants an ACPI event handler run
> > when a certain gpio interrupt is triggered, and the HW reduced ACPI expects the OS gpio driver to do it.
> 
> OK, so this is an implicit dependency.  If this is the only issue, it
> sounds like the driver can be a module.
> 
> > I haven't followed up on this at all. Can't say if we have any HW reduced baytrail variants out there.
> > 
> > For Lynxpoint there was also some issue that pnpacpi reserved the IO resources before a modular gpio driver could get it,
> > I think it was fixed, might be that baytrail would face same issue.
> 
> Could you give any pointer, if you remember?

Mathias, any progress on this?

Thanks,
-- 
Jean Delvare
SUSE L3 Support