Re: [PATCH 0/7] Add MMIO serial ports support and SPCR detection

[Benjamin Herrenschmidt]

On Fri, 2022-09-02 at 16:12 +1000, Benjamin Herrenschmidt wrote:
> This series improves our legacy serial support to add the ability
> to use MMIO based serial ports on x86 and to use ACPI's SPCR to
> automatically configure the default port.
> 
> An MMIO serial port can be specified explicitely using the
> "mmio," prefix for the --port argument to the 'serial' command,
> the register access size can also be specified via a suffix,
> and when 'serial' is used without arguments, it will try to use
> an ACPI SPCR entry (if any) to add the default port and configure
> it appropriately (speed, parity etc...)

I forgot to mention that typically MMIO UARTs are found on AWS EC2
"metal" instances, whose firmware also conveniently populates SPCR.

This allows grub serial to work on these.

Cheers,
Ben.