DDR Overclocking on XU4

A new higher DDR frequency is now available on XU4 series.
Both of Android and Ubuntu supports the frequency set,
and only Android provides DRAM governor interface.

On Android, you can adjust DDR frequency and governor using a new ODROID Utility.

# cat /sys/class/devfreq/exynos5-devfreq-mif/available_governors
simple_exynos   performance

# cat /sys/class/devfreq/exynos5-devfreq-mif/available_frequencies
165000  206000  275000  413000  543000  633000  728000  825000  933000

ODROID Utility has been updated with the new release version.
You can change devfreq governor and frequency using it.

On kernel 4.9, you can change ddr frequency using boot.ini interface.
The available frequency set is 933MHz, 825MHz, 728MHz and 633MHz
and the default one is 825MHz.
As we check the benchmark score using mbw, about 10% improvement can be expected.

Please find ddr_freq in boot.ini and change the value.

...
# DRAM Frequency
# Sets the LPDDR3 memory frequency
# Supported values: 933 825 728 633 (MHZ)
setenv ddr_freq 825
...
# set DDR frequency
dmc ${ddr_freq}
...

And then please make sure to reboot the system.

# sudo reboot

Here is a AnTuTu benchmark score.
We checked the following two cases.

• Case 1 : cpu governor - performance / devfreq governor - performance / devfreq clock - 825MHz
• Case 2 : cpu governor - performance / devfreq governor - performance / devfreq clock - 933MHz