Hi Gerd,

Thanks,
Chao

On 2024/3/15 18:34, Gerd Hoffmann wrote:

On Fri, Mar 15, 2024 at 06:19:12PM +0800, Chao Li wrote:

Hi Gerd,


Thanks,
Chao
On 2024/3/15 17:36, Gerd Hoffmann wrote:

On Mon, Mar 11, 2024 at 05:39:08PM +0800, Chao Li wrote:

Add a early serial port output library into LoongArchVirt that named
EarlyFdtSerialPortLib16550, this library is referenced from
MdeModulePkg.

Why create your own copy?  What are the differences to
MdeModulePkg/Library/BaseSerialPortLib16550?

This library is used in the PEI stage, same as the Hook Library, LoongArch
QEMU is runs on flash in PEI stage, MdeModule version does not support to
get the SerialRegisterBase via registers or HOB or FDT,

It uses PcdSerialRegisterBase.

Having a quick look at the PCD code it looks like the PCD are stored in
in a HOB (gPcdDataBaseHobGuid), so setting dynamic PCDs should work even
when running directly from flash.

I guess if the PCD type is FixedAtbuild, then it might not be in the HOB, because the global symbols will be in the GOT table. And it really doesn't work in the flash stage(I tried it before and I just tried it again).


take care,
  Gerd

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