enable i915 rc6 save 7 watt on kernel 3.2

[Chen Wei <weichen027@gmail.com>]

Hi List,

Since recently upgraded to kernel 3.2, the core temperature on my laptop
seems raised few degrees. An external power meter shows big difference
in power consumption. The power usage raised from 15w on kernel 2.6.39,
to 22w on kernel 3.2.1. A bit of google later, it was suggested that
enable i915_enable_rc6 parameter may improves power consumption as well
as graphic performance. And indeed it is, after put
“i915.i915_enable_rc6=1” in grub config, the overall power usage drops
to 15w, while the glxgears score increases from 39xxFPS to 47xxFPS.

The system: i5-2410M, using integrated HD3000 GPU
            Debian Squeeze with backports xorg



-- 
Chen Wei