Re: [edk2-devel] [PATCH v2 15/30] EmbeddedPkg: Add PcdPrePiCpuIoSize width for LOONGARCH64

["Chao Li" <lichao@loongson.cn>]

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Hi Pedro,

I think this size is the CPU IO or PCI IO space width, like you saied, 
LoongArch doesn't mapped the IO ports, but it has IO area.

For example, it can map the LPC IO or PCI IO ports onto the physical 
addres space and register the CPU IO or PCI IO protocols to access them.

The *Loongson.dsc* of edk2-platforms sets this value to 32. I think this 
value is too wide since most IO device only use 16-bit width, so I 
changed this value from 32 to 16 at this point.


Thanks,
Chao
On 2023/11/16 16:15, Pedro Falcato wrote:
> On Wed, Nov 15, 2023 at 6:55 PM Leif Lindholm<quic_llindhol@quicinc.com>  wrote:
>> On 2023-11-06 03:29, Chao Li wrote:
>>> Added LoongArch64 architecture CPU IO width.
>>>
>>> https://bugzilla.tianocore.org/show_bug.cgi?id=4584
>>>
>>> Cc: Leif Lindholm<quic_llindhol@quicinc.com>
>>> Cc: Ard Biesheuvel<ardb+tianocore@kernel.org>
>>> Cc: Abner Chang<abner.chang@amd.com>
>>> Cc: Daniel Schaefer<git@danielschaefer.me>
>>> Signed-off-by: Chao Li<lichao@loongson.cn>
>> Reviewed-by: Leif Lindholm<quic_llindhol@quicinc.com>
>>
>> I note that as a result of this we are now definining this token
>> individually for 5 different architectures, in order to provide two
>> different default values. We should probably look at consolidating
>> those, but that responsibility doesn't have to land on this set.
>>
>> /
>>       Leif
>>
>>> ---
>>>    EmbeddedPkg/EmbeddedPkg.dec | 3 +++
>>>    1 file changed, 3 insertions(+)
>>>
>>> diff --git a/EmbeddedPkg/EmbeddedPkg.dec b/EmbeddedPkg/EmbeddedPkg.dec
>>> index 341ef5e6a6..241d4f3acc 100644
>>> --- a/EmbeddedPkg/EmbeddedPkg.dec
>>> +++ b/EmbeddedPkg/EmbeddedPkg.dec
>>> @@ -165,6 +165,9 @@
>>>    [PcdsFixedAtBuild.X64]
>>>      gEmbeddedTokenSpaceGuid.PcdPrePiCpuIoSize|16|UINT8|0x00000011
>>>
>>> +[PcdsFixedAtBuild.LOONGARCH64]
>>> +  gEmbeddedTokenSpaceGuid.PcdPrePiCpuIoSize|16|UINT8|0x00000011
>>> +
> Leif,
>
> Can you clarify the meaning of PcdPrePiCpuIoSize? I was thinking it's
> supposed to be the size of the port-mapped IO for the
> architecture/platform (as hinted by in X64 = IA32 = 16, and ARM=0),
> but from a quick git grep I can tell that
> 1) most platforms define it to something else (ArmVirt defines it to
> 16, real platforms have a plethora of other values)
> 2) gEmbeddedTokenSpaceGuid.PcdPrePiCpuIoSize has no internal consumer
> in EmbeddedPkg, but only in ArmPlatformPkg and LoongArchQemuPkg (and
> BeagleBoardPkg's PrePi)
> 3) Platform/Loongson/LoongArchQemuPkg/Loongson.dec:
> gEmbeddedTokenSpaceGuid.PcdPrePiCpuIoSize|0|UINT8|0x00010001 <-- ??
>
> and FWIW, LoongArch does not seem to have port-mapped IO at all.
>


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