[Gta04-owner] [Community] GTA04 power management [was: About cost and business models for community hardware]

Neil Brown neilb at suse.de
Wed Sep 30 01:18:04 CEST 2015


"H. Nikolaus Schaller" <hns at goldelico.com> writes:

> Hi Neil,
>
> Am 29.09.2015 um 02:45 schrieb Neil Brown <neilb at suse.de>:
>
>> "H. Nikolaus Schaller" <hns at goldelico.com> writes:
>>>> 
>>>> I think Radek ‘lost interest' because of lack of some of the lower level points in my list above, principally the battery consumption.
>> 
>> Battery consumption is the main issue that depresses my enthusiasm.
>> It *seems* insoluble.  It probably isn't, but I haven't found a way
>> forward.
>
> I think we should address it a little more analytically.
>
> IMHO we have two problems with more modern kernels:
> * they do not yet have all features (e.g. we are still lacking e.g. hardware voice routing and some other features)
> * device tree and CPU power management has changed significantly - and faster than we can understand the changes
>
> Therefore we have no stable basis ("all features work") to optimize power.
>
> Regarding power saving I think we have to address:
> * all peripherals are properly turned off in power-down mode
> * RAM is in self refresh
> * CPU is sleeping in lowest possible state
> * until a call is coming in, a button is pressed or USB power is plugged in
>
> So which parts are not working well?

That's the $60,000 question.  The only measurement I have to suggest any
problem is that the power drain on the battery is too high.  I have
looked at every component and every driver in every way I know how and I
cannot see a difference between 4.2 and 3.7, but 4.2 uses nearly twice
the current in suspend.
All the regulators that can be turned of are off.  All the sensors that
can't be turned off are in their lowest power state, the RAM refresh
programming is identical in the two kernels (or I tried copying the
relevant code from 3.7 to 4.2 and it made no difference).  The CPU seems
to be reaching the same low-power state.
There is clearly something that I'm missing, but I'm at a loss to
identify it.

> Is this related to our code or to CPU core driver?
> How (well) does the N900 (RX51) mainline code handle this?
>
>> 
>>> 
>>> Well, with 3.7 it was almost good.
>> 
>> I would say 3.7 is just barely usable - if you have a new battery.
>> 
>>> 
>>> A problem for me is that QtMoko has some very nice tools to support battery consumption measurements. But because it does neither run on 3.12 or later kernels, we can’t even test battery consumption easily. How to improve the kernel if a good GUI is missing.
>> 
>> Measuring battery usage isn't that hard.  In the simplest case you just
>> need to log the time (seconds) and the charge-now value from the
>> bq27000 and graph those.  I log them on every 'suspend' and 'resume' so I
>> can easily get data.
>
> Yes, there are other techniques, but QtMoko already provides such
> tools.

But as QtMoko is not available, that doesn't seem relevant.

>
>> 
>> I find it a bit harder at present because all of my batteries with
>> bq27000 in them have died.
>
> Oops. How does this come? I now have the first of several that appears
> to have a problem (charges within short time and is then empty...).

I don't know much about battery chemistry, but I assume there is some
shelf-life issue.

>
>>  I've got a Nokia BL-5C in my phone at the
>> moment.
>> I ripped the bq27000 board off one of the dead batteries and managed to
>> attach it to another BL-5C so I can do measurements, but only on my old
>> "spare" board (which has lost its USB connector so I need WIFI for all
>> networking...)
>
> For the GTA04A5 board there will be an additional bq27621 chip on the main
> board to measure battery status. So even a battery w/o bq27000 can be measured.
> But I don't know the precision.

That's an excellent idea.  In the battery is best of course, but on the
board as well means we don't have to depend on the battery.


>
>> 
>> If I could even get current mainline down to 3.7 power usage levels I'd
>> probably be motivated to keep working on upstreaming things, but I've
>> hit a brick all there too.
>
> The question is in which subsystem the problem is located? Where do
> you hit bricks? What is not working as you expect?

As I said only one thing is not working as expected.  Power usage is too
high.

Thanks,
NeilBrown

>
> Probably we should discuss more about such issues and help
> each other instead of individually trying to run against walls in small
> black boxes.
>
> BR,
> Nikolaus
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