GTA02 is now an expensive brick / pcf50633 defaults
mail at mmontour.net
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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