Zhao Yakui <yakui.zhao@xxxxxxxxx> writes: > 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). Looking at the coreboot source. It is indeed defined for Nvidia, SIS, AMD and several others. A lot of boards use: outb(0x02, 0xcf9); outb(0x06, 0xcf9); Instead of just writing a plain 6. I think at least on some machines there is a requirement for a low to hight transition. > 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. Right. The only scary question is will a motherboard hang if you write to 0xcf9. If we don't know of an example where writing to 0xcf9 will prevent us from getting to the next reset method then adding a generic 0xcf9 is safe. If we are totally paranoid we can build of a whitelist of motherboards where writing to 0xcf9 works. By reading and checkup on the chipset docs, but don't make the mistake of thinking 0xcf9 is an Intel only thing. Eric -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
