Re: 2.6.33-rc3: pci host bridge windows ignored (works with pci=use_crs)

Bjorn Helgaas
2010-01-14T18:08:05Z

On Thursday 14 January 2010 12:46:22 am Yinghai Lu wrote:
> On 01/13/2010 05:24 AM, Jeff Garrett wrote:
> > On Wed, Jan 13, 2010 at 12:45:17AM -0800, Yinghai Lu wrote:
> >> On Wed, Jan 13, 2010 at 12:44 AM, Yinghai Lu <yinghai@kernel.org> wrote:
> >>> On Tue, Jan 12, 2010 at 9:37 PM, Jeff Garrett <jeff@jgarrett.org> wrote:
> >>>> Took a stab at getting the right emails. If I missed anyone, sorry...
> >>>>
> >>>> I have a desktop machine with a radeon HD 4850, and on recent kernels
> >>>> the radeon driver has failed with the message "No valid linear
> >>>> framebuffer address". lspci on the broken configuration showed the
> >>>> first memory region at d0000000 of the radeon card to be ignored. dmesg
> >>>> showed there to be a host bridge window at that address which was also
> >>>> ignored.

> >>> it seems HW IOH only can use [e000000 - fdffffff] under that bridge...
> >>>
> >>> and _CRS said the peer root bus could use [c000000 - dfffffff]
> >>>
> >>> could be that we need to check other register to decide if we can use
> >>> reading from ioh reg directly.

> not sure why [0xc000000 - 0xcffffff] should work with 00:07.0
>
> checked with intel doc, that is out of scope to LMMIOL register...
>
> really don't know how it works with your platform.

I wonder about that [mem 0xc0000000-0xcfffffff] range, too. But as
far as I can tell, we don't actually try to use that anywhere yet.
(We assign part of that range to the 00:1c.0 bridge to bus 03, but
I don't see any devices actually using it.)

One problem I see is that _CRS includes the [mem 0xd0000000-0xdfffffff]
range, but intel_bus.c didn't find it. We DO need this range for the
Radeon, and the Radeon works with "pci=use_crs", so the host bridge must
be routing it.

I think this must be a detail of the Intel host bridge, not something
specific to Jeff's Dell system. This problem should affect all systems
using that host bridge.

PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0xe0000000-0xefffffff] (base 0xe0000000)

ACPI: PCI Root Bridge [PCI0] (0000:00)
pci_root PNP0A08:00: host bridge window [mem 0xc0000000-0xdfffffff]
pci_root PNP0A08:00: host bridge window [mem 0xf0000000-0xfed8ffff]

IOH bus: [00, fb]
IOH bus: 00 index 1 mmio: [e0000000, fdffffff]

pci 0000:00:07.0: PCI bridge to [bus 04-04]
pci 0000:00:07.0: bridge window [mem 0xd0000000-0xdfffffff 64bit pref]
pci 0000:04:00.0: reg 10: [mem 0xd0000000-0xdfffffff 64bit pref]

Another problem is that intel_bus.c didn't remove the MMCONFIG region
[mem 0xe0000000-0xefffffff] from the window. I think there's code there
to do that, but there must be something wrong with it.

Bjorn