Official wiki page
http://odroid.com/dokuwiki/doku.php?id=en:c2_adjust_ddrclk
Guide to change DDR Clock by android update and recovery.
Open
https://dn.odroid.com/S905/BootLoader/ODROID-C2/
Download files.
updatepackage-odroidc2-ddr-408.zip
updatepackage-odroidc2-ddr-792.zip
updatepackage-odroidc2-ddr-912.zip
updatepackage-odroidc2-ddr-1104.zip
Open Utility app.
Select "Package install from storage"
Select "File Manager" -> Download folder
Select updatepackage-odroidc2-ddr-xxx.zip wanted DDR clock.
Recovery!
After reboot, you can check the DDR configuration using the following logs of boot loader if you have a usb-uart module kit.
BL2 Built : 11:44:26, Nov 25 2015.
gxb gfb13a3b-c2 - jcao@wonton
Board ID = 8
set vcck to 1100 mv
set vddee to 1070 mv
CPU clk: 1536MHz
DDR channel setting: DDR0 Rank0+1 same
DDR0: 2048MB(auto) @ 1104MHz(2T)-14