Power management support in Chromium OS

[Sergii Kovalchuk]

Hi all,

We are working on power management support in Chromium OS on ARM-based
board. The board itself has some good things to adjust beyond ordinary
kernel support - such as scaling down GPU/RAM clocks (when not
needed), real-time adjustments of CPU cache sizes etc.

Currently, most of the powerd/powerman daemons functionality is not
working for us and we see a lot of hardcoded sysfs and proc paths to
work with light sensor, backlight and other stuff for CR-48.

We see the following issues:

- Screen resolution re-configuration part is using XRandr library
functions, therefore it is not clean, why backlight control code is
using /sys/class/backlight/<dev>/brightness directly.
- Audio detector queries /proc/asound/card0/pcm0p/sub0/status to
detect audio activities
- Light sensor code is CR-48 specific. Maybe not, however, in any
case, accessing light sensor at hardcoded path of the like "/sys/bus/
iio/devices/device0/illuminance0_input" doesn't look good
- It is not clear, why two power management daemons exist - most of
the functionality of powerman, as lower power management interface can
be moved directly into powerd?

Is there any plans to get rid of hardcoded stuff and make the power
daemons more generic, so we wouldn't have any platform dependencies?
If so, is this work in progress or it is sheduled for some later time
in future?
If this work is not started yet, then where can I find some
architectual documents, describing Chromium OS power management?

[Sonny Rao]

+ power team

I think the power team is working on reorganizing some of the powerd
stuff in R14
perhaps they can address some of the issues or could take a look at
any patches you might have

Sonny

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[Chris Masone]

The reason for powerm and powerd is to split the required level of privilege.  One runs as root so it can do special things.  Everything that does not need that privilege is split off into the other daemon.

Also, one of the benefits of targeting a narrow hardware profile for Google Chrome OS devices is that we can assume and hardcode some things, allowing us to keep the code simpler and faster.  I'd be against compromising simplicity, speed or security in order to support non-supported devices :-)

[sanjay...@gmail.com]

DearyAll,

 

  I am quite curious to know current power management suport on Chromium OS R25.

 

   Are there any references / performance parameters analysis available w.r.t. any reference HW platform ) available?

 

  I appreciate if someone can throw some light on it.

 

regds

Sanjay

[Sameer Nanda]

Sanjay,

This is how battery life testing is done for Chrome OS devices:

http://dev.chromium.org/chromium-os/testing/power-testing

Let me know if you have any specific questions that the above doesn't answer.

--
Sameer