yp-r0: improve the charging code

Some people reported strange charging times and
strange battery life.
Charging by OF: 25 hours; RB: 18 hours
It has been found that there are at least two issues here:

1) the way of getting battery charging status wasn't
really accurate. This attempts to fix that issue.
This patch also simplifies some code (opening a
device is no more needed, for example).

To technically explain, battery charging implies first a constant
current mode (where the voltage increases) and then a constant
voltage mode (where, obviously, the voltage reads more or less
the same). The old way the End Of Charge was detected was based solely
on the voltage, while now it is based on chip's EOC interrupt,
which should be more accurate.

2) OF explicitly sets a constant current 350 mA, while we usually had
55 mA (by as3543 default).
This wasn't discovered before since there is a caching problem
("an accurate guess") in the Samsung power mgmt Linux module,
thus its debugging dumper wasn't really working, reporting a 55 mA current.
Strangely this option should have been set by the bootloader
but apparently it does not.

Some testing is still needed, but I confirm that with this patch
I could run a benchmark for 25 hours (vs. 18 hours), by charging
within Rockbox of course.

Change-Id: I3bd921e86b9018d1cc3c720d15cc46896e8490b3

0 files changed, 0 insertions, 0 deletions