Crowdfunding an Ubuntu smartphone

[NeilBrown]

On Sat, 24 Aug 2013 15:31:19 +0200 "Dr. H. Nikolaus Schaller"
<hns at goldelico.com> wrote:

> Hm. That sounds quite different from the situation about 1 year ago when
> you did the first releases of QtMoko and I always thought that the
> 3.7 kernel is working well enough, so that I started to add new features.
> 
> Has it become worse since then?

I like drawing graphs.  So I did - see attachment.

For the last year or so my GTA04 has been logging the power usage during
suspend for every suspend cycle longer than a few seconds.  I do this by 
reading the "charge_now" value from the bq27000 in the battery, comparing the
"before" and "after" values, and dividing by the number of seconds.

I currently have my phone configured to wake from suspend every 5 minutes,
check that the modem is still working, and go back to suspend.  This has
helped collect quite a lot of values.

To get the graphs I collected all those values, discarded negative numbers
(when the battery was charging) and a few numbers that were clearly
ridiculous (numbers more than 1 amp), and sorted the remainder.


So we get a cumulative frequency graph of different current levels.

The red line ('/tmp/uamp') is for the last couple of days since last reboot. 
This is running 3.7 with offmode disabled.
The green line ('tmp/uamp2') is for the last year, running a variety of
different kernels.

Obviously there is a very different number of samples in each. 342 in uamp
10031 in uamp2.  So I normalised the X values so the graphs are comparable.
They are much the same shape which suggests  the pattern is fairly robust.

The Y axis is microamps.
The green values below 20000 (20mA) are with offmode enabled I assume.
The red values are all greater because I have offmode turned off to improve
reliability.

The steps are a bit of a surprise.  They are all about 2mA.  I don't think
this is an artefact of the precision with which measurements are taken as the
charge value read from the battery has a much higher precision.
I think it must be an actual 2mA difference in (average) current usage.
This could be 2mA more for the whole time, or 4mA more with a 50% duty cycle
etc.

So if we can make off-mode really usable (which possibly means find and fix
some bug in the omap usb code) and if we can find out what is causing these
2mA steps and resolve that, then might might be a little closer to
acceptable power usage.

I might try running for a while with the modem turned off and see what result
I get.

NeilBrown
-------------- next part --------------
A non-text attachment was scrubbed...
Name: current.png
Type: image/png
Size: 4589 bytes
Desc: not available
URL: <http://lists.openmoko.org/pipermail/community/attachments/20130827/32aeb444/attachment-0001.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 828 bytes
Desc: not available
URL: <http://lists.openmoko.org/pipermail/community/attachments/20130827/32aeb444/attachment-0001.sig>