Re: [edk2-devel] [edk2-platforms][PATCH 1/1] AmpereAltraPkg: Update ArmPlatformLib to work with changed ARM_CORE_INFO

["Rebecca Cran" <rebecca@bsdio.com>]

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On 1/17/23 09:40, Ard Biesheuvel wrote:

> On Tue, 17 Jan 2023 at 13:55, Rebecca Cran<rebecca@quicinc.com>  wrote:
>> I was under the impression that this is becoming a more standard format?
>>
> If this is not defined in an ARM spec somewhere, we shouldn't add it
> to ArmPkg at this point.

 From what I've found, the ARM specs such as the Arm Architecture 
Reference Manual for A-profile architecture don't define the meaning of 
the affinity fields? That appears to be left up to the individual Arm 
core TRMs.

For example, the Cortex-X2 TRM says:

Affinity level 0. This is the affinity level that is most significant 
for determining PE behavior. Higher affinity
levels are increasingly less significant in determining PE behavior. The 
assigned value of the MPIDR.{Aff2,
Aff1, Aff0} or AArch64-MPIDR_EL1.{Aff3, Aff2, Aff1, Aff0} set of fields 
of each PE must be unique within the
system as a whole.
0b00000000
Only one thread.


Affinity level 1. See the description of Aff0 for more information.
Value read from the CPUID configuration pins. Identification number for 
each CPU in an cluster counting from
zero.


Affinity level 2. See the description of Aff0 for more information.
The value will be determined by the CLUSTERIDAFF2 configuration pins.


Affinity level 3. See the description of Aff0 for more information.
The value will be determined by the CLUSTERIDAFF3 configuration pins.


-- 
Rebecca Cran

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