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

[Marcelo Tosatti]

On Mon, Jul 16, 2007 at 02:47:10PM -0400, Dan Williams wrote:
> 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...  

I agree. I don't see the utility of power button suspend given the
target should be automatic suspend whenever possible.

> 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.