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

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Date:	Sat, 08 Jan 2011 10:58:01 +0100
From:	Jiri Slaby <jirislaby@...il.com>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
CC:	Jiri Slaby <jslaby@...e.cz>, jbarnes@...tuousgeek.org,
	linux-pci@...r.kernel.org, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Thomas Renninger <trenn@...e.de>
Subject: Re: [PATCH 1/1] PCI: tune up ICH4 quirk for broken BIOSes

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.

>>> ACPI probably reports this region via the FADT (the GPE PM register
>>> blocks) and possibly a PNP0C02 device.  These will probably report
>>> something that doesn't conflict with the legacy IDE ports, i.e., a
>>> subset of the 0x100-0x17f range.
>>>
>>> Ooooh, I notice in the bugzilla that something's wrong with SMBIOS
>>> (comment 29) and ACPI is disabled because we couldn't find the
>>> RSDP (dmesg in comment 27).  What sort of machine is this, anyway?
>>> We didn't find PNPBIOS, either.
>>
>> Hmm, it looks like some old crap. What exact information you would like
>> to know? I've just asked if ACPI is not disabled in BIOS. There should
>> be no machine without ACPI running still in the 21st century, I think.
> 
> I'm just wondering if the machine actually does have ACPI, but
> there's some Linux problem related to finding the tables.  If it's
> really old enough, that wouldn't be so surprising, but I see USB
> and gigabit NIC hardware, so it's not truly ancient.

The box is:
http://www.xembedded.com/content/vme/processors/xvme-690.php
and has ACPI, but the user disabled ACPI (I don't know why yet).

thanks,
-- 
js
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