Re: [PATCH 10/10] x86, ACPI: default to reboot via ACPI (again)

H. Peter Anvin
2008-11-13T03:19:00Z

Zhao Yakui wrote:
>
> Peter Anvin suggests that OS attempt reboot via 0xCF9 port if avaiable.
> This is not very good. 0xCF9 I/O port is the reset control register
> defined in Intel ICH6/7/8/9 chipset. In theory it is effective for Intel
> chipset. Maybe it is not applied for other chipset(For example: Nvidia,
> ALI, VIA). There exists a laptop in bug 11942, in which the 0xCF9 I/O
> port is defined as the RESET_REG. But unfortunately it can't be rebooted
> Via 0xCF9 I/O port.
> In fact although the 0xCF9 is defined for Intel ICH chipset, it
> doesn't mean that all the box based on ICH chipset can be rebooted via
> 0xCF9 I/O port. For example: we have a laptop based on intel ICH6
> chipset that can't be rebooted by writing the 0x06 to 0xCF9 I/O port.
>

Port CF9 isn't universal, but other vendors are increasingly
implementing it -- I know ALi are in their more recent chipsets. Either
way, I agree that we need to figure out how to get ACPI to work, but CF9
is a low risk fallback before going to the KBC.

-hpa