[Gta04-owner] Modem off

NeilBrown neilb at suse.de
Wed Nov 13 00:10:05 CET 2013


On Tue, 12 Nov 2013 21:04:22 +0100 "Dr. H. Nikolaus Schaller"
<hns at goldelico.com> wrote:

> 
> Am 11.11.2013 um 23:49 schrieb NeilBrown:
> 
> > On Mon, 11 Nov 2013 16:38:31 +0100 Andreas Kemnade <andreas at kemnade.info>
> > wrote:
> > 
> >>> 
> >>> I look forward to hearing of your results.
> >> 
> >> At the moment I even cannot reproduce your the lower currents when the
> >> module is removed or unbind is done (when the modem does not show up on
> >> the bus). I measured current_now directly after suspend and retried also
> >> with that 5-min average using charge_now.
> > 
> > What current do you measure? 
> > Is it consistent over several measurements?
> > What kernel are you using?
> > 
> >> 
> >>> Meanwhile, here is a result that turned out more effective than I expected....
> >>> 
> >>> I've automated some parts of my power-usage-monitoring a bit more.  With my
> >>> phone running normally with USB enabled etc with my current 3.7 kernel, the
> >>> average-current-over-5-minutes frequency histogram looks like:
> >>> 
> >> does this mean, modem shows up on the usb bus during the tests?
> > 
> > For those tests, yes.  I've done a number of tests with the modem disabled,
> > and some with the modem enabled.
> > 
> > With the modem disable and the ehci-hcd module loaded and unloaded, on a 3.7
> > kernel I get 
> > 
> > 19411 69
> > 21567 24
> > 43056 1
> > 
> > With the modem enabled I get
> > 
> > 23728 44
> > 25884 120
> > 28057 31
> > 30207 6
> > 32358 1
> > 36684 1
> > 51699 1
> > 75488 1
> > 
> > 
> > With the pulldown removed I get
> > 
> > 17251 45
> 
> Getting down to 17 mA is already really good. And shows how effective the pull-down-removal is.
> 
> > 19410 143
> > 21561 36
> > 23717 5
> > 25888 2
> > 30203 2
> > 43038 1
> > 45527 1
> > 49525 1
> > 243729 1
> 
> Ok, this is quite consistent with a modem that is waking up from time to time and drawing 30-50 mA.
> Depending on when you sample you will see all values between.

That certainly explains much of the variability.  But even with the modem
turned off I see some variability.
The 243mA is rather high, but very uncommon.
30mA above the minimum is the most I've seen with the modem off.

> 
> > 
> > 
> > And all of these numbers are very close to multiples of 2.15mA.
> 
> That may be some effect of the ADC precision.

I had thought that I had checked and found that not to be consistent with my
observations, but I had it wrong.

If I watch the charge_now value on the bq27000 it changes by alternately 178
and 179.  So presumably the precision is 178.5 and it rounds off.
So it can report each decrease of 178.5 micro Amp Hours (uAH).

A current of 2.15mA for one hour would be 2150 uAH.  For 5 minutes it would
be 179uAH, so that is exactly the granularity I can measure.
More precisely, 178.5uAH * 12 = 2.142mA is the granularity for 5 minute
measurements.

Thanks,
NeilBrown
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