On 01/14/2011 01:15 AM, Linus Torvalds wrote:
> On Thu, Jan 13, 2011 at 3:19 PM, Bjorn Helgaas <bjorn.helgaas@xxxxxx> wrote:
>>
>> I think we're back to the question of why we have the ICH4 quirk in
>> the first place, and I don't know the answer to that.
>
> Iirc, there were several laptops that didn't have the ACPI region
> mentioned in any of the regular places, and we'd allocate the PCMCIA
> IO region on top of them. The machine would boot, but if anybody ever
> inserted a PCCard into the machine, the first access to the IO region
> would generally just halt it (because it was trying to read the
> PCCard, but the APCI region decodes first, and then the read from that
> usually put the CPU in a sleep state that it would never wake up from
> for obvious reasons).
>
> So we do want the ICH4 quirk.
Yes, this is an "official" way how ICH4 (and later) advertises the region.
The original commit says:
commit df4ba87cfc2239aa85e21178fca35cf6644a6dd1
Author: Linus Torvalds <torvalds@xxxxxxxxxxxxx>
Date: Thu Oct 23 17:52:25 2003 -0700
Add a quirk for the Intel ICH-[45] to add special ACPI regions.
This fixes resource conflicts due to IO decode that doesn't show
up with a normal PCI probe (we do similar quirks for most other
chipsets). Without it, the kernel doesn't know about some magic
IO decodes for the chips.
>> Maybe you could make the ICH4 quirk only claim the region if it's
>> above PCIBIOS_MIN_IO, i.e., if it's in the area where we could put
>> another PCI device on top of it?
>
> That may well be the best solution - we'd only mark it reserved if it
> might conflict with a dynamic allocation, and if it conflicts with
> other motherboard resources (like the IDE ports), then we don't know
> what the decode priority is anyway, so..
>
> In this case, it looks like the legacy IDE ports get decoded before
> the dynamic BAR's. Which is not too much of a surprise (fixed
> addresses tend to be the first to get decoded).
I will attach 2 patches for this as a reply. I created 2 variants:
A is for all quirk
B is only for ICH4 and ICH6
thanks,
--
js
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