Re: [RFC v2 2/2] hw/riscv: Add server platform reference machine

[Heinrich Schuchardt <heinrich.schuchardt@canonical.com>]

On 3/22/24 08:14, Marcin Juszkiewicz wrote:
> W dniu 22.03.2024 o 05:55, Alistair Francis pisze:
>> I see no mention of device trees in the spec, but I do see ACPI. Do we
>> really expect a server platform to use DTs?
> 
> This platform "kind of" follows sbsa-ref where we have very minimalistic 
> device tree sharing information qemu->firmware.
> 
> libfdt is small, format is known and describes hardware. Firmware is 
> free to make use of it in any way it wants.
> 
> On sbsa-ref we parse DT in TF-A (base firmware) and provide hardware 
> information to higher level (edk2) via SMC mechanism. Then EDK2 creates 
> ACPI tables and provide them to the Operating System.

We should ensure that only either an ACPI table or a device-tree 
description is passed to the OS and not both, e.g. when using

     qemu-system-riscv64 -kernel vmlinux -M sbsa-ref

But that requirement is not machine specific.

Best regards

Heinrich

> 
> In physical system some parts of information provided in DT would be 
> read by firmware from onboard Embedded Controller chip.
> 
>> These functions should be shared with the virt machine if we really do
>> want DTs, but I'm not convinced we do
>