power management experiences with joyride-1572

[Richard A. Smith]

Chris Ball wrote:

>    >> Can I wake up 10 seconds from now?  Is there a timer in any of the
>    >> hardware that is left running?
> 
>    > Yes, but the software does not support this yet.  See bug #4606:
>    > http://dev.laptop.org/ticket/4606
> 
> We don't *use* the southbridge RTC wakeup, but it's not strictly true
> that we don't support it.  You can set your own wakeups easily:
> 
>    # rtcwake -s 120
>    <after 30s, the laptop should suspend due to idleness>
>    <after another 90s, the laptop should wake itself>
> 
> rtcwake is in the OLPC build already.
> 
> - Chris.

RTC wakeups have a chance of hitting #1835 because the EC cannot prevent 
the short cycle of the control line to the voltage regulator so we don't 
use them.  Andres has discussed prohibiting RTC wakeups in kernel space 
but I suggested we put that in the "don't do that" category since he has 
higher priority stuff to worry about.

The safe way to schedule a future wake up will be to use a EC timer.

The framework for this exists but I don't have the kernel facing EC 
command plumbed yet.  This timer will allow you to schedule a wakeup 
with about 10ms resolution up to 24 days in the future.

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