Re: Add support for ACPI Module Device ACPI0004?

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.

Thanks,
sephe

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