[Bug 212] Charging seems completely broken

bugzilla-daemon at bugzilla.openmoko.org bugzilla-daemon at bugzilla.openmoko.org
Sat Mar 10 19:32:52 CET 2007


laforge at openmoko.org changed:

           What    |Removed                     |Added
                 CC|                            |sean_chiang at fic.com.tw
         AssignedTo|sean_chiang at fic.com.tw      |werner at openmoko.org

------- Additional Comments From laforge at openmoko.org  2007-03-10 19:32 -------
I think what might happen here is that we get into some loop where 

1) the PMU decides that the battery voltage is high enough to boot
2) it switches on the CPU, which in turn switches on various peripherals, most
notably high-power peripherals such as backlight
3) due to the high current draw, the battery voltage decreases below the
threshold of the PMU
4) the PMU powers the device off
5) due to no more current draw [or 100mA charger], the battery voltage increases
again to a level above the threshold
6) GOTO 1

So the big question is how to prevent this from happening.

a) we could set a higher Vlowbat (minimum battery voltage) threshold.  This
sucks because we would shut down the phone even before the battery is empty.

b) we could put some heuristics into u-boot to find out if many reboots are
happening in too short a timeframe.  If we can detect this, we still need a way
to prevent it happening again and again.  We need to find out for what reason
the PMU decides to power up in the first place.

In order to debug this, I would recommend (Werner?) a patch to u-boot which
dumps the 'power up reason' and interrupt as well as battery voltage monitor
registers to the serial port.  This means once we get into the loop, we should
get those registers on the serial console and can deduct what's happening

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