Power Saving modes on BBB?

Gábor Paller gaborpaller at gmail.com
Thu Jul 30 10:52:37 UTC 2015


Here is what I have:
root at localhost:~# cat
/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
cat: /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq: No such file or
dire
ctory

root at localhost:~# ls
/sys/devices/system/cpu/cpu0/cpufreq/
ls: cannot access /sys/devices/system/cpu/cpu0/cpufreq/: No such file or
directo
ry

root at localhost:~# ls
/sys/devices/system/cpu/cpu0/
crash_notes       of_node  power
topology
crash_notes_size  online   subsystem  uevent

TI SDK uses the ondemand governor and all the sys files are correctly in
place.

Again:
root at localhost:~# uname
-a
Linux localhost.localdomain 3.19.0-18-generic #18-Ubuntu SMP Tue May 19
18:34:38
 UTC 2015 armv7l armv7l armv7l GNU/Linux

This is a 15.04 Snappy on BBB without any kernel hacking.

"is this under the same userspace too (i.e. are you sure it is kernel
induced and not some bad userspace component) ?"

My test is the following. I created an SD card from the stock Snappy image,
flashed it and booted it. I waited for the boot sequence to finish and
waited for the idle prompt. I measure 340 mA of consumption. I did the same
with the TI SDK and I measure 250 mA. Hence the 40% difference.

As with any Linux distribution it is not only the "kernel" that is running
in any of these cases but a bunch of drivers/daemons too. But there is no
userspace component in these cases, at least I did not install/run any.

Regards,
Gabor

On Thu, Jul 30, 2015 at 11:27 AM, Oliver Grawert <ogra at ubuntu.com> wrote:

> hi,
> Am Donnerstag, den 30.07.2015, 09:45 +0200 schrieb Gábor Paller:
> > Am I right that the entire cpufreq subsystem is also disfunctional on
> > Snappy BBB?
> here it seems to default to the ondemand governor and to run at 275MHz
> by default on a 15.04 image (and i see it scale up fine up to 720MHz
> when the system gets under load). What governor does the TI kernel
> default to ?
>
> >
> > Snappy consumes 40% more current on idle prompt (boot completed, no
> > user task is running) than the baseline TI SDK
>
> is this under the same userspace too (i.e. are you sure it is kernel
> induced and not some bad userspace component) ?
>
> ciao
>         oli
>
>
>
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