u-boot low-battery handling
mail at mmontour.net
Tue Aug 26 07:23:33 CEST 2008
Andy Green wrote:
> Weurgh it's a scary mess in there -- not your patches the whole U-Boot
> power thing.
I agree there's some nasty stuff, but I think that a lot of it comes
from the hardware and is not u-boot's fault (like the PMU's choice of
which registers are preserved in "save" mode, and which ones reset to
mask-programmed defaults). My head hurts after reading through that
> Maybe the best way to come at this is going to be move GTA02 to Qi which
> has no power handling and fix GTA02 at the same time we allegedly solve
> the GTA03 booting-under-100mA thing. At that point, the bootloader has
> no part in charging action and it just waits for kernel to handle it (as
> it has to anyway).
I haven't looked at Qi yet - maybe that's a project for next weekend.
I don't know if you'll be able to put all of the PMU control logic into
Linux. It seems that it might still make sense to have code in the
earliest bootloader for cases like deeply-discharged batteries (e.g.
turn on the charger, flash an LED, and wait for the voltage to reach
some threshold before powering up the glamo, SD card, and whatever else
is needed to boot Linux).
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