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