Re: [PATCH 1/1] PCI: tune up ICH4 quirk for broken BIOSes

[Bjorn Helgaas <bjorn.helgaas@hp.com>]

On Saturday, January 08, 2011 02:58:01 am Jiri Slaby wrote:
> On 01/08/2011 01:16 AM, Bjorn Helgaas wrote:
> > On Friday, January 07, 2011 04:29:00 pm Jiri Slaby wrote:
> >> On 01/08/2011 12:03 AM, Bjorn Helgaas wrote:
> >>> On Friday, January 07, 2011 01:44:35 pm Jiri Slaby wrote:
> >>>> On 01/06/2011 08:24 PM, Bjorn Helgaas wrote:
> >>>>> Theoretically, ACPI tells us about the GPIO/TCO/etc. regions in a
> >>>>> generic way via namespace devices or something in the static tables.
> >>>>> Is that generic information missing, or is it there and Linux is
> >>>>> ignoring it?  If we're ignoring it, I'd rather fix that.
> >>>>
> >>>> It works for most boxes I would say. Try to google for "claimed by ICH4
> >>>> ACPI/GPIO/TCO", it reports sane ranges like 0400-047f or 4000-407f.
> >>>
> >>> My point is that BIOS should be telling the OS about GPIO/TCO/etc.
> >>> regions via an ACPI mechanism, and, ideally, we would use that rather
> >>> than reading the address out of chipset-dependent registers.
> >>>
> >>> Even though PMBASE says the ACPI registers occupy 128 bytes from
> >>> 0x100-0x17f, it's likely there's no actual conflict between the
> >>> last 16 bytes and the IDE device.
> >>
> >> I wouldn't say so. According to the datasheet 0x60-0x7f of the space
> >> (i.e. 0x160-0x17f here) is for TCO registers. There:
> >> 0x10 -- Software IRQ Generation Register (i.e. 0x170)
> >> 0x11-0x1f -- reserved (0x171-0x17f)
> >>
> >> So at least 0x170 should be conflicting. Unless TCO is unused/disabled
> >> and not mapped there at all. May be that the case?
> > 
> > Maybe.  All your patch does is avoid reserving this 0x100-0x1f7
> > region; it doesn't actually *move* anything.  And the IDE device
> > apparently works at the 0x170 compatibility address.  So the
> > ICH ACPI stuff is still at 0x100-0x17f, so apparently they don't
> > conflict or maybe the ICH ACPI stuff is disabled.  If the box
> > doesn't even have ACPI, I suppose there would be no reason to
> > have the ACPI registers enabled.  Is there something in ICH
> > that tells us whether they're enabled?
> 
> Hmm, there is:
> bit 4: ACPI Enable (ACPI_EN) — R/W.
>   0 = Disable.
>   1 = Decode of the I/O range pointed to by the ACPI Base register is
> enabled, and the ACPI power management function is enabled. Note that
> the APM power management ranges (B2/B3h) are always enabled and are not
> affected by this bit.
> 
> at 0x44 in the bridge conf space. So we should definitely check the value.
> 
> I don't have the actual value in that register when ACPI is disabled in
> BIOS. From the run where acpi=off was passed to the kernel, there is
> 0x10 (i.e. ACPI_EN=1). However I don't know whether ACPI was disabled in
> BIOS at that time.

Checking ACPI_EN before doing anything in the quirk looks like
the simplest thing (if the BIOS actually sets ACPI_EN=0 when
it disables ACPI).

Bjorn