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
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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