Is OLPC going for ACPI support?

[Mitch Bradley]

Manish Regmi wrote:
> Hi all,
>     Will ACPI be used in OLPC. I read a lot of wonderful discussions
> for ACPI. Most of the discussions were against it.
> http://mailman.laptop.org/pipermail/devel/2006-July/000608.html
>
> This doc says some work is going on for ACPI...
> http://wiki.laptop.org/go/Hardware_Power_Domains#Power_management_test_plan_.28work_in_progress.29 
>
>
> But what was the conclusion? Will there be ACPI support on OLPC?

The OLPC OS does not use the ACPI interface, nor does the OLPC firmware 
support it .  The OS drivers perform the appropriate power management 
operations directly, with full knowledge of the behavior of the hardware 
on which they operate.  The firmware exports a low-level suspend-to-RAM 
function in the form of a subroutine.  The OS, after doing whatever 
driver work is necessary, calls that subroutine.  The firmware then 
saves the core state and puts the hardware into a low-power state with 
RAM powered in self-refresh mode.  Upon a wakeup event, the firmware 
restores the core state and returns from the subroutine.

The current size of the firmware suspend/resume code is about 1K.  It is 
written in assembly language, optimized to do its job as quickly as 
possible.  We hope to be able to do "micro sleeps" so fast that the user 
will not realize that the system is sleeping.

OLPC has special hardware features for retaining the image on the screen 
and for performing wireless mesh routing while the main processor is 
powered off.