power management

[Jordan Crouse]

On 28/03/07 21:49 -0500, Gopi Palaniappan wrote:
> 1. Does the hardware support Voltage/Frequency scaling?

No.

> 2. What kind of sleep modes does it support?

Just suspend to RAM.

> 3. Is there an infrastructure for power measurements? Do we have any current
> drain measurements/readings?

The best way to measure overall power consumption is to solder a small
resistor on one of the leads from the power brick (I use a 24 milliohm
resistor).  Then, measure the voltage and do the math.

> 4. Where are you experiencing the instability..is it at the hardware layer
> or the syspend-resume mechanism?

Right now it is instability in the key drivers, but we're pretty close
to getting those resolved.

> 5. Recently we did a lot of cleanup in the kernel to short-circuit the
> default pm_suspend process, which has unnecessary layers that trumps the
> suspends... the biggest one that comes to my mind is the dealing with
> UNINTERRUPTIBLE SLEEP processes. I am not sure if you are experiencing
> similar issues?

Not right now.

> 6. Is there a need for periodic wakeup? on mobile devices its required to
> wakeup almost every minute to update clock display, battery level, rf
> levels.it makes sense to sync up all these activities during the wakeup
> period.I am not sure if a laptop has such a requirement..

We have the infrastructure to do periodic wakeups, but its not clear if
those will be needed or not.  Right now, we're trying to make the most
stable and fastest suspend/resume that we can - we'll find good uses
for a very fast suspend later.

> 7. Usually display/backlight is the biggest sucker of power.. do we use any
> special displays that support partial refresh?

Yes.

> 8. Suspend to RAM is good..it will give an "Instant-On" experience..is this
> in the main kernel now or does it need special patches? If so where can i
> find these patches?

What we have is in the powermgmt tree in the olpc-2.6 git repository on
dev.laptop.org.  When we stabilize the situation, then we'll be able to
provide a bit more detail.

Jordan