Re: [PATCH RESEND v4 0/3] Upgrade ACPI SPCR table to support SPCR table revision 4 format

[Sunil V L <sunilvl@ventanamicro.com>]

Hi Jee Heng,

On Mon, Aug 26, 2024 at 07:04:11AM +0000, JeeHeng Sia wrote:
> 
> 
> > -----Original Message-----
> > From: Sunil V L <sunilvl@ventanamicro.com>
> > Sent: Friday, August 23, 2024 10:29 PM
> > To: JeeHeng Sia <jeeheng.sia@starfivetech.com>
> > Cc: qemu-arm@nongnu.org; qemu-devel@nongnu.org; qemu-riscv@nongnu.org; mst@redhat.com; imammedo@redhat.com;
> > anisinha@redhat.com; peter.maydell@linaro.org; shannon.zhaosl@gmail.com; palmer@dabbelt.com; alistair.francis@wdc.com;
> > bin.meng@windriver.com; liwei1518@gmail.com; dbarboza@ventanamicro.com; zhiwei_liu@linux.alibaba.com
> > Subject: Re: [PATCH RESEND v4 0/3] Upgrade ACPI SPCR table to support SPCR table revision 4 format
> > 
> > Hi Jee Heng,
> > On Fri, Aug 23, 2024 at 04:31:39AM -0700, Sia Jee Heng wrote:
> > > Update the SPCR table to accommodate the SPCR Table revision 4 [1].
> > > The SPCR table has been modified to adhere to the revision 4 format [2].
> > >
> > > Meanwhile, the virt SPCR golden reference file for RISC-V have been updated to
> > > accommodate the SPCR Table revision 4.
> > >
> > > [1]: https://learn.microsoft.com/en-us/windows-hardware/drivers/serports/serial-port-console-redirection-table
> > > [2]: https://github.com/acpica/acpica/pull/931
> > >
> > Just curious - whether this needs changes in linux side as well? Does
> > current linux code work fine with version 4 of SPCR table on RISC-V?
> The current Linux ACPI Table has not yet been updated to support SPCR v4.
> However, Linux RISC-V will be able to use the information in the QEMU's
> SPCR table to boot with behaviour similar to ARM. 
> > 
So, it means even if qemu risc-v SPCR is upgraded to version 4,
current linux continues to work. It may be just able to decode SPCR v2
fields only until enhanced to understand v4 but but doesn't break
anything or crash. Is that correct?

Just wanted to confirm qemu changes can get merged without any
dependency.

Thanks!
Sunil