On Mon, Feb 24, 2020 at 01:27:40PM +0200, Mika Westerberg wrote:
> On Mon, Feb 24, 2020 at 12:51:25PM +0200, Mika Westerberg wrote:
> > > I'm wondering if
> > >
> > > pci_dev_is_present(...);
> > >
> > > returns false here.
> >
> > Well that might also be the case since lspci shows this:
> >
> > 00:1f.0 ISA bridge: Intel Corporation Z390 Chipset LPC/eSPI Controller (rev 10)
> > 00:1f.3 Audio device: Intel Corporation Cannon Lake PCH cAVS (rev 10)
> > 00:1f.4 SMBus: Intel Corporation Cannon Lake PCH SMBus Controller (rev 10)
> >
> > PMC is 1f.2 and not present here. However, it may be that the PMC is
> > still there it just does not "enumerate" because its devid/vendorid are
> > set to 0xffff. Similar hiding was done for the P2SB bridge.
>
> Actually I think this is the case here.
>
> I don't know the iTCO_wdt well enough to say if it could live without
> the ICH_RES_IO_SMI. It looks like this register is used to disable SMI
> generation but not sure how well it works if it is left to BIOS to
> configure. I suppose these systems should use WDAT instead.
>
In practice the region is only used if
if (turn_SMI_watchdog_clear_off >= p->iTCO_version) {
where turn_SMI_watchdog_clear_off is 1 by default. It is also
passed to vendor specific code, but that is only relevant for
really old systems. In short, it isn't really needed for any
recent-generation systems, and could be made optional with
a few lines of code in iTCO_wdt.c.
Guenter
