Power Saving modes on BBB?

g4 at novadsp.com g4 at novadsp.com
Thu Jul 30 10:26:53 UTC 2015


Again not quite sure of the state of play with the current Snappy kernel but IIRC you also need to switch off the PMIC and HDMI to further reduce power consumption. The TI stuff may be doing this for you.

 

Cpufreq-xxx looks good on 4.1 with (for example)

 

------------------------------snip--------------------------------

root at arm:/home/debian# cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq

1000000

root at arm:/home/debian# cpufreq-set -f 300mhz

root at arm:/home/debian# cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq

300000

 

From: Gábor Paller [mailto:gaborpaller at gmail.com] 
Sent: 30 July 2015 08:45
To: Paolo Pisati
Cc: jerry evans; Snappy Devel
Subject: Re: Power Saving modes on BBB?

 

Am I right that the entire cpufreq subsystem is also disfunctional on Snappy BBB?

Snappy consumes 40% more current on idle prompt (boot completed, no user task is running) than the baseline TI SDK and I can't find the frequency scaling files under /sys.

Also, bizarrely, if the BBB is entirely shut down, Snappy still consumes around 120 mA while TI SDK goes down to almost 0.

 

This, along with the lack of power-saving modes is pretty much a showstopper for any serious battery-operated application on Snappy.

Regards,

Gabor

 

On Fri, Jul 24, 2015 at 3:57 PM, Paolo Pisati <paolo.pisati at canonical.com> wrote:

On Thu, Jul 23, 2015 at 6:27 PM, Gábor Paller <gaborpaller at gmail.com> wrote:
> 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

I'm looking into this, but this is as good as upstream goes - if you
want better PM support you should consider using the official TI
kernel:

https://git.ti.com/ti-linux-kernel/ti-linux-kernel/trees/master

albeit i'm facing problems there too.

Can you open an LP bug for this so we track the development?
Thanks.
--
bye,
p.

 

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