Lower GPU clock of ODROID-XU4 for headless servers to save energy

Per default the Mali-T628 GPU inside the ODROID-XU4 will run at maximum speed (600MHz) the whole time.
This doesn’t consume that much energy if there is no load on the GPU but nevertheless you can tune this a little bit if you don’t need the GPU at all.

Your kernel needs the following commit: mali: restore sysfs entries
Newer 3.10 ODROID-XU4 kernels should have this activated. I tested this with my own custom build kernel. You can grab it here. Source.

To lock the GPU frequency to the lowest frequency possible (177MHz) do the following. This will automatically lower the voltage as well (see

cat /sys/devices/11800000.mali/vol

apt-get install sysfsutils
vi /etc/sysfs.conf

---
# lower mali gpu clock to min
devices/11800000.mali/dvfs_max_lock = 177
---

service sysfsutils start

With this change you will lower ODROID-XU4 power consumption by about 0.7W.
The SOC will be 1-2°C cooler as well  Perfect for headless servers.