Re: [PATCH 2/2] arm/virt/acpi: remove _ADR from devices identified by _HID

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Jan 05, 2020 at 07:34:01AM -0500, Michael S. Tsirkin wrote:
> On Thu, Dec 19, 2019 at 02:47:59PM +0800, Heyi Guo wrote:
> > According to ACPI spec, _ADR should be used for device which is on a
> > bus that has a standard enumeration algorithm. It does not make sense
> > to have a _ADR object for devices which already have _HID and will be
> > enumerated by OSPM.
> > 
> > Signed-off-by: Heyi Guo <guoheyi@huawei.com>
> 
> Are you sure? I would think this depends on the ID and the device
> really. E.g. PCI devices all are expected to have _ADR and some of them
> have a _HID.


To clarify I am not commenting on patches.
The spec says this:
	6.1.5 _HID (Hardware ID)

	This object is used to supply OSPM with the device’s PNP ID or ACPI ID. 1

	When describing a platform, use of any _HID objects is optional. However, a _HID object must be

	used to describe any device that will be enumerated by OSPM. OSPM only enumerates a device

	when no bus enumerator can detect the device ID. For example, devices on an ISA bus are

	enumerated by OSPM. Use the _ADR object to describe devices enumerated by bus enumerators

	other than OSPM.


Note: "detect the device ID" not "enumerate the device" which I think
means there's a driver matching this vendor/device ID.

So it seems fine to have _ADR so device is enumerated, and still have
_HID e.g. so ACPI driver can be loaded as fallback if there's
no bus driver.


Note I am not saying the patch itself is not correct.
Maybe these devices are not on any standard bus and that
is why they should not have _ADR? I have not looked.

I am just saying that spec does not seem to imply _HID and _ADR
can't coexist.


> CC Corey who added a device with both HID and ADR to x86 recenly.
> 
> Apropos Corey, why was HID APP0005 chosen?
> 
> > ---
> > Cc: Shannon Zhao <shannon.zhaosl@gmail.com>
> > Cc: Peter Maydell <peter.maydell@linaro.org>
> > Cc: "Michael S. Tsirkin" <mst@redhat.com>
> > Cc: Igor Mammedov <imammedo@redhat.com>
> > Cc: qemu-arm@nongnu.org
> > Cc: qemu-devel@nongnu.org
> > ---
> >  hw/arm/virt-acpi-build.c          |   8 --------
> >  tests/data/acpi/virt/DSDT         | Bin 18449 -> 18426 bytes
> >  tests/data/acpi/virt/DSDT.memhp   | Bin 19786 -> 19763 bytes
> >  tests/data/acpi/virt/DSDT.numamem | Bin 18449 -> 18426 bytes
> >  4 files changed, 8 deletions(-)
> > 
> > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> > index 9f4c7d1889..be752c0ad8 100644
> > --- a/hw/arm/virt-acpi-build.c
> > +++ b/hw/arm/virt-acpi-build.c
> > @@ -78,11 +78,6 @@ static void acpi_dsdt_add_uart(Aml *scope, const MemMapEntry *uart_memmap,
> >                               AML_EXCLUSIVE, &uart_irq, 1));
> >      aml_append(dev, aml_name_decl("_CRS", crs));
> >  
> > -    /* The _ADR entry is used to link this device to the UART described
> > -     * in the SPCR table, i.e. SPCR.base_address.address == _ADR.
> > -     */
> > -    aml_append(dev, aml_name_decl("_ADR", aml_int(uart_memmap->base)));
> > -
> >      aml_append(scope, dev);
> >  }
> >  
> > @@ -170,7 +165,6 @@ static void acpi_dsdt_add_pci(Aml *scope, const MemMapEntry *memmap,
> >      aml_append(dev, aml_name_decl("_CID", aml_string("PNP0A03")));
> >      aml_append(dev, aml_name_decl("_SEG", aml_int(0)));
> >      aml_append(dev, aml_name_decl("_BBN", aml_int(0)));
> > -    aml_append(dev, aml_name_decl("_ADR", aml_int(0)));
> >      aml_append(dev, aml_name_decl("_UID", aml_string("PCI0")));
> >      aml_append(dev, aml_name_decl("_STR", aml_unicode("PCIe 0 Device")));
> >      aml_append(dev, aml_name_decl("_CCA", aml_int(1)));
> > @@ -334,7 +328,6 @@ static void acpi_dsdt_add_gpio(Aml *scope, const MemMapEntry *gpio_memmap,
> >  {
> >      Aml *dev = aml_device("GPO0");
> >      aml_append(dev, aml_name_decl("_HID", aml_string("ARMH0061")));
> > -    aml_append(dev, aml_name_decl("_ADR", aml_int(0)));
> >      aml_append(dev, aml_name_decl("_UID", aml_int(0)));
> >  
> >      Aml *crs = aml_resource_template();
> > @@ -364,7 +357,6 @@ static void acpi_dsdt_add_power_button(Aml *scope)
> >  {
> >      Aml *dev = aml_device(ACPI_POWER_BUTTON_DEVICE);
> >      aml_append(dev, aml_name_decl("_HID", aml_string("PNP0C0C")));
> > -    aml_append(dev, aml_name_decl("_ADR", aml_int(0)));
> >      aml_append(dev, aml_name_decl("_UID", aml_int(0)));
> >      aml_append(scope, dev);
> >  }
> > diff --git a/tests/data/acpi/virt/DSDT b/tests/data/acpi/virt/DSDT
> 
> 
> Please do not include binary changes in acpi patches.
> 
> See comment at the top of tests/bios-tables-test.c for documentation
> on how to update these.
> 
> -- 
> MST