Re: [edk2-devel] [PATCH v1 1/2] OvmfPkg: Add no hardcode version of FtdNorFlashQemuLib

["xianglai" <lixianglai@loongson.cn>]

Hi Marcin:
> W dniu 17.05.2024 o 09:17, Chao Li via groups.io pisze:
>> This library is copied from ArmVirtPkg, in the Arm version, the value of
>> PcdFlashNvStorageVariableBase, PcdFlashNvStorageFtwWorkingBase and
>> PcdFlashNvStorageFtwSpareBase are hardcoded in INC file.
>>
>> This version will calculate them from FDT resource and using the set PCD
>> to store when the NorFlashInitialise is called. By default, the first
>> available flash(not used for storage UEFI code) as NV variable storage
>> medium.
>>
>> In this way, UEFI can better handle the change of flash base address,
>> which is suitable for different cpu architecture board implementation.
>>
>> BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=4770
>>
>> Cc: Ard Biesheuvel<ardb+tianocore@kernel.org>
>> Cc: Leif Lindholm<quic_llindhol@quicinc.com>
>> Cc: Sami Mujawar<sami.mujawar@arm.com>
>> Cc: Gerd Hoffmann<kraxel@redhat.com>
>> Cc: Jiewen Yao<jiewen.yao@intel.com>
>> Signed-off-by: Chao Li<lichao@loongson.cn>
>> Signed-off-by: Xianglai Li<lixianglai@loongson.cn>
>
> Can you split it into driver itself and part which uses DT data to 
> setup parameters?
>
> This way driver can be used on other platforms as well, despite do 
> they hardcode flash data, read it via Firmware Handoff protocol, SMC 
> calls to embedded controller or have other way to keep flash data.

This lib is provided for resolving pfalsh base addresses for virtual 
machines emulated by qemu.

The pfash base address of the arm and riscv architectures emulated by 
qemu is hardcoded in UEFI.
After this lib is committed, arm and riscv can easily use this lib by 
modifying the dsc and VarStore.fdf.inc files.
Later, we will send out the patch of arm and riscv, then arm and riscv 
will also be realized by resolving the pflash base address through fdt.

So, what other qemu emulation platforms do you think will hard-code fdt 
base addresses?:-)
Or are there specific scenarios that require hard-coded pflash base 
addresses?:-)

I admit that there is more flexibility, but do we really need to do 
that?:-)

Thanks!
Xianglai.



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