Re: [edk2-devel] [PATCH v1 17/26] OvmfPkg/LoongArchVirt: Add serial port hook library

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

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Hi Ard and Gerd,


Thanks,
Chao
On 2024/3/15 17:54, Chao Li wrote:
>
> Hi Ard,
>
> On 2024/3/15 17:51, Ard Biesheuvel wrote:
>> On Fri, 15 Mar 2024 at 10:49, Chao Li<lichao@loongson.cn>  wrote:
>>> Hi Gerd,
>>>
>>>
>>> Thanks,
>>> Chao
>>> On 2024/3/15 17:33, Gerd Hoffmann wrote:
>>>
>>> On Mon, Mar 11, 2024 at 05:39:02PM +0800, Chao Li wrote:
>>>
>>> Add a serial port hook library in LoongArchVirt named
>>> Fdt16550SerialProtHookLib, this library is referenced from ArmVirtPkg.
>>>
>>> LoongArch QEMU virtual machine uses register of LOONGARCH_CSR_KS1 to
>>> transfer serial port base addres from the PEI phase to the DXE phase.
>>>
>>> Why use LOONGARCH_CSR_KS1?  Can't you simply set PcdSerialRegisterBase?
>>>
>>> The LoongArch QEMU PEI stage runs on flash and does not allow set PCD operations(memory have not enabled), so the address can only be transferred through a SAVE register.
>>>
>> Then maybe use a HOB instead?
> Ha, I forgot this way, let's me try.

I remember, before committing the first version, I tried to usb the HOB 
in this library, but if the HOB library is referenced, the 
UefiDevicePathLibDevicePathProtocol.inf and UefiLib.inf will be cycle 
consumed, I rememberd the UefiDevicePathLibDevicePathProtocol.inf 
included a constructor that will cause the cycle comsumed.

So, I think it is a better choice for this library to use register KCS1.

>>
> 


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