Question regarding "boot-hartid" DT node

[Heinrich Schuchardt]

On 12/2/21 16:05, Sunil V L wrote:
> Hi All,
>     I am starting this thread to discuss about the "boot-hartid" DT node
>     that is being used in RISC-V Linux EFI stub.
> 
>     As you know, the boot Hart ID is passed in a0 register to the kernel
>     and hence there is actually no need to pass it via DT. However, since
>     EFI stub follows EFI application calling conventions, it needs to
>     know the boot Hart ID so that it can pass it to the proper kernel via
>     a0. For this issue, the solution was to add "/chosen/boot-hartid" in
>     DT. Both EDK2 and u-boot append this node in DT.
> 
>     But above approach causes issue for ACPI since ACPI initialization
>     happens late in the proper kernel. Same is true even if we pass this
>     information via SMBIOS.
> 
>     Do you have any suggestions what can be done in ACPI case? Can we use
>     a UEFI variable with RVI specific GUID to pass this information? This
>     will have the advantage that it can work with either DT or ACPI.
>     Also, we may not need any UEFI spec update. Do you see any issue with
>     this approach? Your inputs will be very helpful.

What happened to your suggestions in

https://linuxplumbersconf.org/event/11/contributions/1099/attachments/781/1602/LPC_2021_ACPI_RISCV_Sunil.pdf

Best regards

Heinrich

> 
> Thanks!
> Sunil
>