Re: [edk2-devel] [PATCH v4 19/37] UefiCpuPkg: Add MMIO method in CpuIo2Dxe

["Ard Biesheuvel" <ardb@kernel.org>]

On Thu, 21 Dec 2023 at 13:11, Chao Li <lichao@loongson.cn> wrote:
>
> Hi Ard,
>
>
> Thanks,
> Chao
> On 2023/12/21 15:31, Ard Biesheuvel wrote:
>
> On Thu, 21 Dec 2023 at 04:48, Chao Li <lichao@loongson.cn> wrote:
>
> ...
>
> Ard,
>
> PcdPciIoTranslationIsEnabled is only use for whether to trigger the Ffio read or write, it seem that only x86 or x64 need them, not others.
>
> When I was submitted the patch V2, CpuIo2Dxe was private to LoongArch, just like Arm and RISC-V. Gerd recommended finding a better place for ArmPciCpuIo2Dxe so that other ARCH can easily use it. And then I found the UefiCpuPkg/CpuIo2Dxe might be able to accommodate the MMIO methods, so I merged them togeter in this change.
>
> I think it makes sense to have a shared implementation under
> UefiCpuPkg or even MdeModulePkg. But merging it with the x86
> implementation using function pointers that are dereferenced at
> runtime seems unnecessary to me.
>
> So what do you suggest? Write some new functions to handle the MMIO method under the CpuIo2Dxe?
>

A given platform will either be able to use port IO, or it will need
to use MMIO translation. So a driver that can do both based on a PCD
is not very useful, it makes more sense to have two different drivers,
and the platform incorporates the one it can use.


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