Re: [PATCH 1/1] EmbeddedPkg/AcpiLib: add GICC table init macro for ACPI 6.3

["Pete Batard" <pete@akeo.ie>]

On 2020.03.30 14:20, Ard Biesheuvel wrote:
> On Mon, 30 Mar 2020 at 15:12, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>>
>> On Mon, 30 Mar 2020 at 15:09, Pete Batard <pete@akeo.ie> wrote:
>>>
>>> On 2020.03.30 14:06, Ard Biesheuvel wrote:
>>>> On Fri, 27 Mar 2020 at 14:06, Pete Batard <pete@akeo.ie> wrote:
>>>>>
>>>>> Incidentally, this is not an [edk2-platform] patch, as the subject line
>>>>> from previous mail seemed to indicate, but an [edk2] patch.
>>>>>
>>>>
>>>> Do we have a user for this?
>>>
>>> Yes we do. I have a pachset lined up that updates the Raspberry Pi ACPI
>>> to 6.3, that has a dependency on this.
>>>
>>
>> But does the RPi have SPE and the associated overflow interrupt?

No, but it doesn't matter since the specs indicate that SPE values can 
be set to zero if unused/non-applicable.

>> ACPI
>> is designed to be backward compatible, so it is perfectly acceptable
>> to use the 6.2 macros in the context of a firmware implementation that
>> complies with 6.3.

This is what happens if you try to use EFI_ACPI_6_0_GICC_STRUCTURE_INIT 
in a 6.3 context:

/usr/src/edk2/MdePkg/Include/IndustryStandard/Acpi10.h:297:33: error: 
excess elements in scalar initializer [-Werror]
  #define EFI_ACPI_RESERVED_BYTE  0x00
                                  ^~~~
Building ... 
/usr/src/edk2/MdePkg/Library/DxeCoreHobLib/DxeCoreHobLib.inf [AARCH64]
/usr/src/edk2/EmbeddedPkg/Include/Library/AcpiLib.h:64:30: note: in 
expansion of macro ‘EFI_ACPI_RESERVED_BYTE’
      {EFI_ACPI_RESERVED_BYTE, EFI_ACPI_RESERVED_BYTE, 
EFI_ACPI_RESERVED_BYTE}         \
                               ^~~~~~~~~~~~~~~~~~~~~~
/usr/src/edk2-platforms/Platform/RaspberryPi/AcpiTables/Madt.aslc:64:5: 
note: in expansion of macro ‘EFI_ACPI_6_0_GICC_STRUCTURE_INIT’
      EFI_ACPI_6_0_GICC_STRUCTURE_INIT (
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The only reason I'm sending an EDK2 patch, which I'd always rather avoid 
so that edk2-platforms patches can be applied faster, is that I haven't 
been able to find a way to make the existing 6.0 macros work in a 6.3 
context, and I expect that this will be the case for others.

>> Or is there another reason you want to update the
>> MADT to 6.3?

I just want to fix the compilation error, as well as make sure that 
folks who need the ACPI 6.3 SPE init can get it without having to spend 
time waiting for an EDK2 patch to be applied.

> BTW, this patch sets the size of the GICC entry to 'sizeof
> (EFI_ACPI_6_0_GIC_STRUCTURE)' so it is likely that the parser will
> choke on it.

The structure size hasn't changed. There were 3 reserved bytes, and now 
there's one reserve byte and one 16-bit word for the SPE.

Since I actually need this patch as part of a platform update, I did 
validate compilation, so, no, the parser doesn't choke on it.

Regards,

/Pete