GTA02 is now an expensive brick / pcf50633 defaults

Mike Montour mail at
Wed Jan 7 19:04:50 CET 2009

Andy Green wrote:

> There's two interesting ideas from Mike though, one is that disable USB
> insert as ON will help by giving longer for VB_SYS to charge and the
> other is leave charger enabled.  For both of these, they are defeated
> (USB insert is ON action, charger disabled) by NOPOWER and we have no
> control then. 

I'm not considering the NOPOWER case, because as you point out there is 
nothing that can be done in software to help with that problem.

Another software workaround for this issue is to never let the main 
battery drain into the cutoff state. The PMU can generate a low-battery 
interrupt. If the FR gets this interrupt, it can re-program the PMU with 
safe settings and then immediately power off the main device and the 
Calypso. The battery will still drain a bit from leakage current and 
self-discharge, but at a much slower rate.

That's the simple version - more work is needed to handle cases like 
hot-swapping batteries while the device is plugged into external power 
(which could also generate a low-battery signal). There should also be 
an opportunity for userspace to do a clean shutdown of the device when 
the battery gets low, but before it reaches the critically-low level to 
trigger an immediate shutdown.

I have not looked at any recent kernels or u-boots (for several months) 
to see if this has already been implemented. It's somewhere on my to-do 

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