There seem to be two memory regions that need to be reserved, otherwise
the system just hangs when running:
$ stress --vm-bytes $(awk '/MemFree/{printf "%d\n", $2 * 0.9;}' < /proc/meminfo)k \
  --vm-keep -m 1

The first memory region is really crucial and without it the system
hangs. I could not find any references to this in Amlogic's GPL kernel
sources.
The second region is used by the "suspend firmware". The u-boot sources
(/arch/arm/cpu/aml_meson/m8/firmwareld.c) state that the suspend
firmware is located at "64M + 15M" which matches CONFIG_MESON_SUSPEND in
the Amlogic GPL kernel sources. The "suspend firmware" is responsible
for waking up the system from suspend state.

This also fixes reading the full SD card as without this the system
would simply hang (probably related to the first memory region, if some
buffer is allocated there).
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>