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

[Chris Ball]

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?

   > * 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.
-- 
Chris Ball   <cjb at laptop.org>