Am 24.03.2017 um 16:47 schrieb Bjorn Helgaas:
On Mon, Mar 13, 2017 at 01:41:35PM +0100, Christian König wrote:
From: Christian König <christian.koenig@xxxxxxx>
Most BIOS don't enable this because of compatibility reasons.
Can you give any more details here? Without more hints, it's hard to
know whether any of the compatibility reasons might apply to Linux as
well.
Unfortunately not, I could try to ask a few more people at AMD if they
know the background.
I was told that there are a few boards which offers that as a BIOS
option, but so far I haven't found any (and I have quite a few here).
My best guess is that older windows versions have a problem with that.
Manually enable a 64bit BAR of 64GB size so that we have
enough room for PCI devices.
From the context, I'm guessing this is enabling a new 64GB window
through the PCI host bridge?
Yes, exactly. Sorry for the confusion.
That might be documented as a "BAR", but
it's not anything the Linux PCI core would recognize as a BAR.
At least the AMD NB documentation calls this the host BARs. But I'm
perfectly fine with any terminology.
How about calling it host bridge window instead?
I think the specs would envision this being done via an ACPI _SRS
method on the PNP0A03 host bridge device. That would be a more
generic path that would work on any host bridge. Did you explore that
possibility? I would prefer to avoid adding device-specific code if
that's possible.
I've checked quite a few boards, but none of them actually implements it
this way.
M$ is working on a new ACPI table to enable this vendor neutral, but I
guess that will still take a while.
I want to support this for all AMD CPU released in the past 5 years or
so, so we are going to deal with a bunch of older boards as well.
+ pci_bus_add_resource(dev->bus, res, 0);
We would need some sort of printk here to explain how this new window
magically appeared.
Good point, consider this done.
But is this actually the right place of doing it? Or would you prefer
something to be added to the probing code?
I think those fixups are applied a bit later, aren't they?
Best regards,
Christian.
