It looks like some or most devices with this gpu can be oc'ed,

maybe changing the line 65 of file
linux-3.0 / drivers / staging / mrst / pvr / services4 / system / intel_drm / sysconfig.c

define SYS_SGX_CLOCK_SPEED (400000000)

into what we want would do the trick

edit: didn't see the #

However, I been looking at how is done in other platforms, check here:
https://github.com/Quarx2k/jordan-kernel/commits?author=Quarx2k

And search for "gpu"

I know, it is specific for omap platforms, but maybe we can find the equivalent.

Its interesting not only because we can gain more performance on games, but also because we can underclock the gpu while its sleeping, and thus, save us some battery.