Re: Add support for ACPI Module Device ACPI0004?

On Friday, April 28, 2017 05:38:32 PM Sepherosa Ziehau wrote:
> On Thu, Apr 27, 2017 at 12:14 AM, John Baldwin <jhb_at_freebsd.org> wrote:
> > On Wednesday, April 26, 2017 09:18:48 AM Sepherosa Ziehau wrote:
> >> On Wed, Apr 26, 2017 at 4:36 AM, John Baldwin <jhb_at_freebsd.org> wrote:
> >> > 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).
> >>
> >> The remove/reassociate vmbus part seems kinda "messy" to me.  I'd just
> >> hook up a new acpi0004 driver, and let vmbus parse the _CRS like what
> >> we did to the hyper-v's pcib0.
> >
> > The acpi_pci driver used to do the remove/reassociate part.  What acpi0
> > should probably be doing is only creating device_t nodes for immediate
> > children.  This would require an ACPI-aware isa0 for LPC devices below
> > the ISA bus in the ACPI namespace.  We haven't done that in part because
> > BIOS vendors are not always consistent in placing LPC devices under an
> > ISA bus.  However, you otherwise have no good way to find your parent
> > ACPI0004 device.  You could perhaps find your ACPI handle, ask for its
> > parent handle, then ask for the device_t of that handle to find the
> > ACPI0004 device, but then you'd need to have all your bus_alloc_resource
> > calls go to that device, not your "real" parent of acpi0, which means
> > you can't use any of the standard bus_alloc_resource() methods like
> > bus_alloc_resource_any() but would have to manually use BUS_ALLOC_RESOURCE
> > with the ACPI0004 device as the explicit first argument.  It is primarily
> > the ability to let ACPI0004's driver transparently intercept all the
> > resource allocation so it can manage that is the reason for "VMBus"
> > to be a child of ACPI0004 rather than its sibling.
> 
> Well, there could be more then one ACPI0004 typed devices, which could
> not form a device tree for vmbus.

Are you saing a vmbus would need resources from multiple ACPI0004 devices?
That would seem a bit odd.  OTOH, if you can have multiple ACPI0004 devices
each with its own VMBus child (in the ACPI namespace) then having the VMBus
be a child of ACPI0004 in new-bus would make it easy to find the "right"
ACPI0004 parent device.

-- 
John Baldwin