Hi Bjorn,
On 21.09.2016 21:18, Bjorn Helgaas wrote:
On Wed, Sep 21, 2016 at 11:58:22AM -0700, Duc Dang wrote:
On Wed, Sep 21, 2016 at 11:04 AM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
On Wed, Sep 21, 2016 at 03:05:49PM +0100, Lorenzo Pieralisi wrote:
The existing x86 practice is to use PNP0C02 devices for this purpose,
and I think we should just follow that practice.
...
My point is that the hard-coding should not be buried in a driver
where it's invisible to the rest of the kernel. If we hard-code it in
a quirk that adds _CRS entries, then the kernel will work just like it
would if the firmware had been correct in the first place. The
resource will appear in /sys/devices/pnp*/*/resources and /proc/iomem,
and if we ever used _SRS to assign or move ACPI devices, we would know
to avoid the bridge resource.
Are you suggesting to add code similar to functions in
linux/drivers/pnp/quirks.c to declare/attach the additional resource
that the host need to have when the resource is not in MCFG table?
Yes, but what I'm suggesting is actually a little stronger. This has
nothing to do with whether a resource is in the MCFG table or not.
I'm suggesting ACPI firmware should always describe the resource. If the
firmware is defective and doesn't describe it, we should add a quirk in
pnp/quirks.c to add a resource for it.
Thanks for pointers Bjorn.
ThunderX is the case where we cannot change firmware, also it has no
PNP0c02 device in tables. So in order to use pnp/quirks.c we would have
to fabricate PNP0c02 in kernel and then add quirk entry. I am looking
for the best place to put such emulation code but it seems not trivial.
Thanks,
Tomasz
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