[Bug 212] Charging seems completely broken

bugzilla-daemon at bugzilla.openmoko.org bugzilla-daemon at bugzilla.openmoko.org
Tue Mar 13 04:59:32 CET 2007


------- Additional Comments From werner at openmoko.org  2007-03-13 04:59 -------
The PMU takes care of properly feeding the battery. All we need to do is tell
it how much current it can draw from the charger. But the problem isn't
deciding how to charge the battery, but to avoid trying to bring up the
system when the battery is too weak.

If we have enough juice to last a whole 7 seconds, we could indeed do the
full USB protocol exchange with the host to get permission to use 500 mA
and/or detect the charger, which also lets us use maximum power.

However, I'm afraid that a battery that's even in worse shape may not give
us enough time to get that far. With the backlight turned off (but the LCM
receiving power), my bv2 still wants 160 mA from the battery while idling
in u-boot.

A possible solution may be to do the USB protocol exchange in u-boot before
anything else if the PMU indicates a charger connect (which can be
misleading). We should be able to do this while staying within the 100 mA
envelope. Once this is done, u-boot can return to standby mode and charge
at full speed.

If the PMU doesn't indicate a charger connect, the normal startup process
would happen. I.e., the user wouldn't have to wait for USB.

But I think we still need a mechanism to catch the phone if it enters that
vicious circle. Something slightly more sophisticated than my current hack,
but not too complex either.

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