[mythtv-users] ACPI sleep problems

Greg Woods greg at gregandeva.net
Mon Sep 19 19:36:35 UTC 2005


On Mon, 2005-09-19 at 20:28 +0100, Steve Hill wrote:
>   Everything I read says I just need to set the 
> wake-up alarm by echoing a time and date to /proc/acpi/alarm and then 
> suspend the machine by doing:
>      echo -n mem > /sys/power/state

Where did you read this? I'd like to know because everything *I* have
read says that ACPI suspend-to-RAM doesn't really work on Linux. I have
never been able to make it work on my laptop; I can get it to suspend to
RAM by doing "echo 3 > /proc/acpi/sleep", but there appears to be no way
to wake it up after that. Suspend-to-disk (so-called "software suspend")
supposedly works but I've never been able to make that work either (and
even if it did, it wouldn't be suitable for this purpose because there's
no way to do a wakeup other than physically powering it on). ACPI is
essentially a power management standard that pushes all the power
management out of the BIOS hardware and into the OS. The more paranoid
among us think this was a ploy by Microsoft to make it harder to run
non-Windows OS's on PC laptops. But either way, the ACPI implementation
in Linux is not very robust as yet. Whether or not it will work will
likely depend on exactly what kernel version you are running and what
motherboard and BIOS chip. But it is highly unlikely that it will be as
simple as echoing something to a /proc or /sys file. If you do manage to
make it work, I'd love to hear about it.

--Greg




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