[Gta04-owner] low battery charging

[Andreas Kemnade]

Hi,

i found time to analyze some of my low battery charging issues (seen
with various kernels, tested
with /sys/class/power_supply/twl4030_usb/device/max_current = 500mA:
I have several bad usb cables with cannot provide 600mA without going
below the disconnect voltage so i am always using 500mA by default.

Precharging:
If i start to cycle with a flat battery so that gta04 does not go on,
it often goes on when i stop at traffic lights or steep hills (and then
soon goes off again...). I cannot 100% always reproduce this with
another power source but i have not measured vbat during that. But the
timing seems to precise to be just random. Maybe there is a voltage
range in which the gta04 switches on when the charging current goes
below a certain threshold. I guess I have to dig into the TRM again.

Device is on, Battery voltage < 3.2 V (i do not know the exact limit
here):
That can be from precharging.
If power is connected:
If automatic charging is enabled, 100mA from usb is drawn which means
that the device is slowly discharged if not in suspend. No action taken
by userspace, replugging does not help.
If linear charging is enabled, the configured maximum current is drawn
from usb (or something reduced if the power source is not that powerful
and voltage breaks down), so real charging occurs.

Greetings
Andreas Kemnade