[Letux-kernel] generic-adc-battery

H. Nikolaus Schaller hns at goldelico.com
Wed Feb 10 08:49:52 CET 2016


Am 10.02.2016 um 07:38 schrieb Andreas Kemnade <andreas at kemnade.info>:

> Hi,
> 
> On Tue, 9 Feb 2016 09:55:50 +0100
> "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> 
>> Hi,
>> @Andreas:
>> 
>> yes, the status is broken. We just know how much current is coming in through USB.
>> We do not know how it is split between system and charging.
>> 
>> I think we can compensate by charge-current-offset-mA. I.e. if we subtract
>> the default power consumption, any excess current from USB will charge.
>> 
> maybe we can also use some dU magic. There are ModelGauge things from Maxim.
> I think they do something like that.

Ok, that would need to store some voltage samples over time and detect the differences.

> 
>> I.e. offset: 400mA
>> 
> Maybe there could be a range named "unknown",
> That state is possible in the interface.

Well, it is not really "unknown" - it is not precisely enough known which is almost the same
but only almost.

Anyways, I have found the slides Pavel was referring to. But they don't show the
formula:

http://cseweb.ucsd.edu/~trosing/lectures/battery.pdf

Here is the full response (including an extended formula by Pavel for the range below
3.3V and 19%):

https://lkml.org/lkml/2015/4/1/557

Now I understand a little why Pavel is behaving so strangely since that discussion.

He did some technical contribution and we did not appreciate enough. I don't remember
why, but most likely because the discussion already took more time than we had for it
and running such discussions is time consuming (and distracting from other important
things). Upstreaming is a full-day-job...

So we should probably pick up at exactly this mail. Something like:

What about adding this formula as a default for the voltage-to-percent-conversion to
the generic-adc-battery driver (and converting it to DT)? Would that be a better solution
than a table driven and twl4030 only driver?

BR,
Nikolaus



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