Availability of XO-1.5 ATest-2 machines

Richard A. Smith richard at laptop.org
Mon Jul 20 16:02:02 EDT 2009

Benjamin M. Schwartz wrote:

> Yes. You can use the rtcwake command to set wakeup timers for the future
> from userspace.  However, my impression is that this is only safe if the
> timer is at least 2 seconds in the future at the time of suspend, due to a
> potential race with the EC.

Not a race with the EC.  Rtcwake does not go through the EC therefore 
the EC cannot guarantee you don't violate the minimum off time for the 
cpu rail.  Violations result in a cpu lockup.

Paul Fox's olpc-powerd does extra checking to see that an rtcwake is 
never scheduled such that it might violate that timing.  Thats all 
that's required.

For XO-1.5 firmware I've implemented timed EC wakeups.  If that gets 
used for 1.5 then it's an easy backport to XO-1.  It does not offer much 
additional advantage over using the rtc except <1s wakeups.

Richard Smith  <richard at laptop.org>
One Laptop Per Child

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