On 2025/4/23 下午4:36, Li Chen wrote:
Hi Bibo,
---- On Wed, 23 Apr 2025 14:27:36 +0800 bibo mao <maob...@loongson.cn> wrote
---
>
>
> On 2025/4/22 下午8:03, Li Chen wrote:
> > This series introduces a new machine option, spcr=on|off, allowing users
> > to disable the ACPI SPCR (Serial Port Console Redirection) table.
> > By default, SPCR is enabled. Disabling it can help ensure that the guest
> console behavior is determined solely by kernel command-line parameters
> Hi Li,
>
> SPCR only provides serial port HW description information.
>
> However how to use is determined by Linux kernel, Can you describe the
> detailed scenario which is unintended serial console configurations
> imposed by firmware?
Yes, it is decided by the kernel, more specifically, by how
architecture-specific code utilizes acpi_parse_spcr. For example, in the 5.10
arm64 kernel
https://elixir.bootlin.com/linux/v5.10.236/source/arch/arm64/kernel/acpi.c#L236,
it passes true to acpi_parse_spcr's param enable_console.
So, SPCR consoles are respected by Arm64 Linux by default. Therefore, even
without a console=ttyAMA0 configuration, ttyAMA0 is still added as a preferred
console
and used by printk.
About serial port, there is ACPI SPCR table and DSDT table. About how to
use, it is decided by kernel, so I think that it probably kernel usage
issue.
However I have no opposing view with your patch, adding option
"spcr=on|off" sounds good.
Regards
Bibo Mao
Regards,
Li
