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.
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