Several devices, including the Fuze+ have great trouble recovering from
very low battery states, even in the presence of USB power. This is partly
due to buggy Sigmatel boot stubs and Rockbox bootloader doing unsafe power
operations on boot (should be fixed soon). In such a state, it is impossible
to boot either the OF and Rockbox, so only the recovery mode is available.
With this commit, mkimxboot can now create a very small stub which only
does one thing but does it well: setup charging to recover from any situation.
It does not provide a fancy charging screen or whatever, screen will just
stay black and the device will slowly charge at ~100mA. When the battery is
back to a normal level, just unplug and boot normally.
Change-Id: Ib50880af85ed1f4f64a7eed0f2221e73c889c351
Now boot to RB if play/pause is pressed during 1 second, and to OF if
back is pressed 1 second. Otherwise power off. If hold is on, also power
off. In USB and alarm context, always boot and back determines OF vs RB.
Change-Id: Ie1d6c971901d6473255461cc7d71a5ee3177ecad
Rewrite dualboot in C code instead of assembly. Also properly
handle subtarget and simply Makefile. This should make the
dualboot stub more readable and easier to extend. The new code
also gracefully handles power up from RTC alarm on imx233.
Change-Id: I7c225254b1463a97e76b6cb4de476aa2d2c9d2f9
