Idle States (C-States)

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Posted by Victor Marmol

on Feb 01 2011 02:28 AM

Hi, I'm working on measuring the power consumption of an OMAP3530 (BeagleBoard) in different cpu active and cpu idle states. I am not able to get Linux kernel support for c-states however. I've tried the latest version of the Angstrom distribution and that has a somewhat working CPUIdle subsystem. It is able to go down to the first idle C-state but no further even though it recognizes 7 possible c-states.

Doas anyone know a kernel version, branch, or configuration that has good support for c-states? Does TI provide a sample Linux kernel with software support for the chip's features?

Thanks! Any ideas or resources are greatly appreciated!

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Posted by Abhilash Koyamangalath

on Feb 02 2011 03:25 AM

Prodigy180 points

Victor,

I faced a similar problem of not entering any states deeper than the first ( with 2.6.37). I found that this was getting disallowed because that the uart time-out values were zeros ( which means no timeout).

I put finite values ( small integers) into /sys/devices/platform/omap/omap_uart.[0-3]/sleep_timeout and it worked.

This might help.

-Abhilash

Posted by Victor Marmol

on Feb 02 2011 23:15 PM

Prodigy20 points

Hi Abhilash,

Thanks for the tip! I actually didn't have a /sys/devices/platform/omap/omap_uart.[0-3]/sleep_timeout but I did the following:

echo 1 > /debug/pm_debug/sleep_while_idle

echo 1 > /debug/pm_debug/enable_off_mode

echo 1 > /debug/pm_debug/voltage_off_while_idle

And the board got all the way down to C3! While not the lowest state, its still pretty good.

If you don't mind my asking, I am a bit curious about your setup. The 2.6.37 kernel is from the OMAP branch? Is this up and running on a BeagleBoard? Do you use some pre-build distro or roll your own?

Thanks again!

Victor Marmol

Posted by Enrique Contreras

on Jun 12 2012 10:21 AM

Prodigy10 points

Hi,

I also want to change the work state in the cpuidle driver that runs in a OMAP3 BeagleBoard C4, but I have the same problem and it's that I only can change from state0 to state1 and vice versa. I have tried the changes proposed in previous posts, but my problem persists. The OS used is an Angstrom distribution with a Linux kernel version 2.6.32. Someone has any idea about what is the cause of this problem and how solved it?

Thanks!!

Enrique Contreras