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 at amd.com> >> >> 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.
