Re: Add support for ACPI Module Device ACPI0004?

On Thursday, April 20, 2017 02:29:30 AM Dexuan Cui wrote:
> > From: John Baldwin [mailto:jhb_at_freebsd.org]
> > Sent: Thursday, April 20, 2017 02:34
> > > Can we add the support of "ACPI0004" with the below one-line change?
> > >
> > >  acpi_sysres_probe(device_t dev)
> > >  {
> > > -    static char *sysres_ids[] = { "PNP0C01", "PNP0C02", NULL };
> > > +    static char *sysres_ids[] = { "PNP0C01", "PNP0C02", "ACPI0004", NULL };
> > >
> > Hmm, so the role of C01 and C02 is to reserve system resources, though we
> > in turn allow any child of acpi0 to suballocate those ranges (since historically
> > c01 and c02 tend to allocate I/O ranges that are then used by things like the
> > EC, PS/2 keyboard controller, etc.).  From my reading of ACPI0004 in the ACPI
> > 6.1 spec it's not quite clear that ACPI0004 is like that?  In particular, it
> > seems that 004 should only allow direct children to suballocate?  This
> > change might work, but it will allow more devices to allocate the ranges in
> >  _CRS than otherwise.
> > 
> > Do you have an acpidump from a guest system that contains an ACPI0004
> > node that you can share?
> > 
> > John Baldwin
> 
> Hi John,
> Thanks for the help!
> 
> Please see the attached file, which is got by
> "acpidump -dt | gzip -c9 > acpidump.dt.gz"
> 
> In the dump, we can see the "ACPI0004" node (VMOD) is the parent of
> "VMBus" (VMBS). 
> It looks the _CRS of ACPI0004 is dynamically generated. Though we can't
> see the length of the MMIO range in the dumped asl code, it does have
> a 512MB MMIO range [0xFE0000000, 0xFFFFFFFFF].
> 
> It looks FreeBSD can't detect ACPI0004 automatically.
> With the above one-line change, I can first find the child device 
> acpi_sysresource0 of acpi0, then call AcpiWalkResources() to get
> the _CRS of acpi_sysresource0, i.e. the 512MB MMIO range.
> 
> If you think we shouldn't touch acpi_sysresource0 here, I guess
> we can add a new small driver for ACPI0004, just like we added VMBus
> driver as a child device of acpi0?

Hmmm, so looking at this, the "right" thing is probably to have a device
driver for the ACPI0004 device that parses its _CRS and then allows its
child devices to sub-allocate resources from the ranges in _CRS.  However,
this would mean make VMBus be a child of the ACPI0004 device.  Suppose
we called the ACPI0004 driver 'acpi_module' then the 'acpi_module0' device
would need to create a child device for all of its child devices.  Right
now acpi0 also creates devices for them which is somewhat messy (acpi0
creates child devices anywhere in its namespace that have a valid _HID).
You can find those duplicates and remove them during acpi_module0's attach
routine before creating its own child device_t devices.  (We associate
a device_t with each Handle when creating device_t's for ACPI handles
which is how you can find the old device that is a direct child of acpi0
so that it can be removed).

Then when you are the "VMBus" device_t your parent is the ACPI0004 device
so you can easily talk to it to obtain resources (probably ACPI0004 can
just intercept bus_if.m resource methods to manage the resources).

-- 
John Baldwin