Am 12.04.2017 um 18:55 schrieb Bjorn Helgaas:
[SNIP]
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.
I've never seen _SRS for host bridges either. I'm curious about what
sort of new table will be proposed. It seems like the existing ACPI
resource framework could manage it, but I certainly don't know all the
issues.
No idea either since I'm not involved into that. My job is to get it
working on the existing hw generations and that alone is enough work :)
My best guess is that MS is going to either make _SRS on the host bridge
or a pre-configured 64bit window mandatory for the BIOS.
+ 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?
Logically, this should be done before we enumerate the PCI devices
below the host bridge, so a PCI device fixup is not the ideal place
for it, but it might be the most practical.
Since the modification must be done on a device connected to the root
bus I run into quite a chicken and egg problem if I try to do it before
the enumeration.
I could imagine some sort of quirk like the ones in
drivers/pnp/quirks.c that could add the window to the host bridge _CRS
and program the bridge to open it. But the PCI host bridges aren't
handled through the path that applies those fixups, and it would be
messy to identify your bridges (you currently use PCI vendor/device
IDs, which are only available after enumerating the device). So this
doesn't seem like a viable strategy.
I've tried that, but gave up rather quickly. Looks like the current
approach indeed work find even with "pci=realloc", so I'm going to stick
with that.
Regards,
Christian.
