[Testing] Final review for Power Management Requirements, Trial-2

[Dan Williams]

On Mon, 2007-07-16 at 11:14 -0400, Chris Ball wrote:
> Hi Kim,
> 
> Thanks for writing this up and for the reminder to comment.
> 
>    > PW1 Whenever possible the laptop should go into DCON mode, which is
>    > the lowest possible power usage to conserve battery life. If the
>    > laptop is powered up and left running without intervention with
>    > default 'suspend' power settings, the laptop battery life should
>    > exceed 24 hours.
> 
> Just switching to DCON mode will not have enough of an effect to get
> battery life up to 24 hours.  The CPU is still turned on in DCON mode;
> all that's off is the memory traffic between the CPU and DCON.  We would
> still expect to be drawing CPU + backlight + wireless, which is going to
> be around 3-4 watts ~= 5 hours.
> 
> Maybe the second sentence is talking about the battery life we get in
> *suspend* mode, not DCON mode; if so, it should be in a different
> section.  That's what's implied by "the lowest possible power usage",
> I think?
> 
>    > PW1.1 While in DCON mode or when coming in and out of DCON mode,
>    > the student will not notice anything as the screen will remain
>    > on. (See Screen off below, which WILL be noticed by the student).
> 
> Agreed.
> 
>    > * PW2 After 10 minutes of inactivity through keyboard, mouse,
>    > directional, or gamepad keys, the screen will turn completely off
>    > (black).
> 
> Disagree.  Watching a two-hour movie would mean you have to deal with
> the screen turning off until a wakeup press twelve times.  I think we
> can rephrase this to:
> 
> * PW2 After 10 minutes of inactivity through keyboard, mouse,
>   directional, or gamepad keys, the screen will turn completely off
>   (black), unless a running activity has asked to inhibit this timeout.
> 
>    * PW3 The screen will turn back on at the press of any
>    > key on the keyboard, mouse, directional or gamepad keys. The back
>    > light will come back on to the level it was before the screen saver
>    > turned on.
> 
> Agreed.
> 
>    > * PW4 Pushing the 'Suspend/Resume' button (used to be the power
>    > button), will put the laptop into suspend mode, which includes
>    > Screen off.  + PW4.1 In suspend mode, the laptop will continue to
>    > forward wireless packets if it is in the path between another
>    > laptop and an internet connection (school server, XO as MPP).
>    > + PW4.2 Pushing the 'Suspend/Resume' button when the laptop is
>    > suspended will return it to powered on state with the same
>    > activities running as before it suspended.
> 
> We need to add a section on what happens when the lid closes -- it
> should be "Suspend including Screen Off", as already defined.  But,
> if closing the lid achieves that, it's not clear that there's a good
> reason for the power button suspend to exist, since it does the same
> thing.  I'd originally thought that power button suspend would leave
> the screen on (either with backlight on or backlight off).  Jim, any
> ideas?

I guess I don't really see the utility of the power button suspend as
we've got it now.  It's pretty well useless.  I can't really think of
what the power button suspend should do differently than a lid-closed
suspend (they both should turn go into "only wifi on" mode), and having
two methods seems redundant, but whatever...  In any case, I just think
having the panel and backlight on but suspended via the power button
isn't really useful.  Ohm should be idle-suspending you in between
gamekey presses anyway for soemthing like ebook mode, you shouldn't have
to push the button.

Dan

>    > * PW5 When the battery gets to its defined shut down level, whether
>    > in suspend mode or full operational mode, it will shut down
>    > gracefully, without data destruction.
> 
> Agreed.  (For FRS, we like the idea of having a suspend-to-NAND that can
> be used when the battery is low and there is enough space on the NAND,
> so that the kids don't have to reboot completely every time their
> battery runs out.  That isn't well-specified enough to go in this
> document yet, though.)
> 
>    > * PW6 The student must be able to execute a full power down of the
>    > laptop from the Sugar home view.
> 
> Agreed.
> 
> (Sorry if I sound like I'm complaining without taking the time to
> rewrite -- I'm happy to work on the rewriting once we have consensus.)
> 
> - Chris.