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

[Andrew Jones <drjones@redhat.com>]

On Mon, Jan 13, 2020 at 09:57:55PM +0800, Guoheyi wrote:
> 
> 在 2020/1/13 20:08, Igor Mammedov 写道:
> > On Thu, 19 Dec 2019 14:47:59 +0800
> > Heyi Guo <guoheyi@huawei.com> 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 it's does not make sense?
> > Have you checked commit f264d51d8, that added _ADR?
> 
> I searched in SPCR spec and ACPI spec, but didn't find such requirement for
> serial port device description.
> 
> Hi Andrew,
> 
> Could you help to explain the reason?

tl;dr: It was a mistake and I agree with removing _ADR from SPCR.

The long version is that ACPI support for ARM took a long time to get
merged upstream. In the meantime Linaro and Red Hat had ACPI support
in their downstream trees. The initial, never upstreamed implementation
of Linux SPCR support used _ADR to find the console UART (probably
because some vendor hacked their ACPI tables that way). I made the
mistake of using the out-of-tree Linux kernel code as my "specification".

Upstream kernels never had this problem and I don't think we need to
worry about any of those downstream kernels which did. They'd be five
years old by now anyway.

Thanks,
drew

> 
> Thanks,
> 
> Heyi
> 
> 
> 
> > 
> > > ---
> > > 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
> > > index b5895cb22446860a0b9be3d32ec856feb388be4c..a759ff739a071d5fbf50519a6aea296e5e0f1e0c 100644
> > > GIT binary patch
> > > delta 72
> > > zcmbO@f$>*ABbQ6COUN&G1_q{66S<_BT5Bh&t1wzk^tIeLL4lL8ZSqD=gU!!5x$Pt+
> > > c1HyxxIO07#U3dfh0t}oDoEbRcLp@y>07w882mk;8
> > > 
> > > delta 94
> > > zcmey>&p2@cBbQ6CONgKc0|V26iCof5J#`b+RhV2^Ci+-%al|{i1o1F1FmP^cRp4ao
> > > tnY@hCfEg&X`7$S;oxFTNc#soEyoaX?Z-8HbfwO@#16Tu)4E1zj005fm7mWY_
> > > 
> > > diff --git a/tests/data/acpi/virt/DSDT.memhp b/tests/data/acpi/virt/DSDT.memhp
> > > index 69ad844f65d047973a3e55198beecd45a35b8fce..6e5cc61977e4cd24f765fec0693f75a528c144c1 100644
> > > GIT binary patch
> > > delta 72
> > > zcmX>#i*fTTMlP3Nmk?uL1_q|eiCof5eHSLGt1wzk^tIeLL4lL8ZSqD=gU!!5U7RH)
> > > c1HyxxIO07#U3dfh0t}oDoEbRcLp@y>03)CjmjD0&
> > > 
> > > delta 94
> > > zcmdlyi}BPfMlP3Nmk=*s1_q}3iCof5t(PXMt1!8;O!Tqj;)r*23F2X3VBp-?s=&$E
> > > tGkF=O0W(l&^JPwVXL<R6@E|9Scn?n(-T=P<17`zg2CxPo8S3f6006qZ7#siq
> > > 
> > > diff --git a/tests/data/acpi/virt/DSDT.numamem b/tests/data/acpi/virt/DSDT.numamem
> > > index b5895cb22446860a0b9be3d32ec856feb388be4c..a759ff739a071d5fbf50519a6aea296e5e0f1e0c 100644
> > > GIT binary patch
> > > delta 72
> > > zcmbO@f$>*ABbQ6COUN&G1_q{66S<_BT5Bh&t1wzk^tIeLL4lL8ZSqD=gU!!5x$Pt+
> > > c1HyxxIO07#U3dfh0t}oDoEbRcLp@y>07w882mk;8
> > > 
> > > delta 94
> > > zcmey>&p2@cBbQ6CONgKc0|V26iCof5J#`b+RhV2^Ci+-%al|{i1o1F1FmP^cRp4ao
> > > tnY@hCfEg&X`7$S;oxFTNc#soEyoaX?Z-8HbfwO@#16Tu)4E1zj005fm7mWY_
> > > 
> > 
> > .
> 
>