Hi!

quoted

quoted

quoted

to introduce coefficients for temperature and discharge rate?

What do you mean? Nothing like that is used in current driver why do
we need to add it?

Well, conversion between Li-ion's voltage and state of charge at 0
current is well known:

We can’t measure at 0 current since the OMAP is driven from battery
and charger and may also draw some mA…

Yes, but you know how many mA you are taking just now. So if you knew
the internal resistance, you could compute the voltage at 0
current. (And it should also work during charging, as long as you know
how much current is going in.)

quoted

   def percent(m, v):
   	u = 0.0387-(1.4523*(3.7835-v))
       if u < 0:
           return 0
         return (0.1966+math.sqrt(u))*100

And there's not much to calibrate there, and it should become library
helper function; there's no need to write it to every single dts.

The charge/discharge difference is due to internal battery resistance,
and Ohm's law. (Then, you should not need different values for
charging/discharging case.)

Yes, and that also depends on the board and battery type. So you always
need to specify some battery specific coefficient for that in the DT.

Yes, and that coefficient should be internal battery resistance ;-).

We simply did choose a table, because calculating the right coefficients
is more complex and getting the table values can easily be done from
running one full charge-discharge-charge cycle.

Well.. One set of coefficients would be kind of ok. But you are doing
two, because it really depends on current, not charge/discharge. So
why not do it right, for all currents...?

quoted

With your aproach, you'll get lower percentage when phone is under
load vs. idle. Taking internal resistance into account would give you
more precise readings. (Attached, old patch for zaurus shows the
needed computation).

This is why we have a charging and a discharging table to compensate
for this effect.

Yes, but there's very different current during "idle" phone and during
call (for example). So yes, you are compensating for different current
during charge and discharge, but it is possible to do better.

quoted

I guess this should go into library somewhere, because many machines
need similar code.

Is a library easier to maintain and handle than just a set of table
values?

I think so, yes, because otherwise you need a set of tables for each
machine.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html