There are two ways in which a flashed firmware image may be booted, which we
call mode 0 and mode 1 - see the Flash-boot-modes write-up in the
freecalypso-tools repository for the details.  All TI official firmwares
including our TCS211 reference version have used flash boot mode 1, and the
present Magnetite firmware is unchanged in this regard.

Some FCDEV3B boards have a non-understood hardware problem that causes flash
boot to fail (the visible symptom is a dead hang with even JTAG not working)
when the firmware image in flash uses boot mode 1.  It is not currently known
how many boards are affected by this problem; it is possible that the Mother's
S/N 001 board is the only one that exhibits this oddity.

Once the discovery was made that the flash boot problem occurs only when the fw
image uses flash boot mode 1, a workaround became apparent: switch to using
flash boot mode 0.  Redesigning Magnetite fw to use interrupt and exception
vectors in the ROM branching to 0x80001C-0x800034 in IRAM is not in line with
the Mother's vision, but a surgical hack to make the Magnetite fw flash image
receive control from the boot ROM in mode 0, disable the boot ROM via the
FFFF:FB10 register and jump to 0 as if in mode 1 is quite doable, and it
accomplishes the job of producing a flash image of FC Magnetite that boots
without a hitch on the flash-boot-challenged FCDEV3B.

The standard FC Magnetite build is unchanged and unaffected, i.e., the hack in
question is NOT applied by default.  However, if you have a board that has
trouble booting the regular Magnetite fwimage.bin that uses flash boot mode 1,
you can run 'make fwimage.mode0' in your build directory to get an image patched
with the flash boot mode 0 hack.