Custom resolution for HDMI on NanoPC T3

Hi!

Following the Wiki [1], I'm trying to get my NanoPC T3 work with a monitor,
which is connected to the HDMI port using an HDMI -> DVI converter and does
not support any of the HD video modes.

I would like to set the resolution to 1680x1050@60Hz. Modifying the file
arch/arm/mach-s5p6818/dev-display.c on line 354, changing the resolution to
1680x1050 there, recompiling and updating the kernel on the SD card did not
work. My screen still goes back to powersave after displaying garbage for a
few seconds when booting the NanoPC.

Could someone please help me with that?

[1]
http://wiki.friendlyarm.com/wiki/index.php/NanoPC-T3#LCD.2FHDMI_Resolution

We are sorry to tell you that currently the HDMI driver only tested 1080P
and 720P, and the driver is lack of support for resolution 1600 x 900 and
1366 x 768, the CPU user manual doesn't describe these two modes too,
therefore, we don't recommend that you use these modes.
FROM :https://github.com/friendlyarm/linux-3.4.y/issues/6