[Intel-gfx] How to disable the internal graphics device of Q45 for lower power consumption

[joseph wang]

Hi all,
I wonder if there is a way to disable or power off the built-in graphics
device that is integrated in chipset if it is not used for most of the
time, for instance, on servers. What I have tried is, experiment on Q45
chipset, set bit 3 and 4 of register 'deven' at offset 54-57h in the PCI
configuration space belonging to device 0 function 0. The datasheet of Q45
tells setting these bits can disable the internal graphics(deveice 2
function 0 and 1). I tried and it turned out that if the VGA cable is
connected, setting the bits leads up to shut-off of signal and the power
meter shows less dissipation. That is great. But if I unplug the VGA cable,
I can also see the same drop in degree as much as which if I disable the
device. That means if cable is unconnected, disable the device cannot
further reduce the power consumption. So I am guessing the graphics device
is not fully powered off by this method. The questions goes, is there any
way which can fully power off the device or at least put it into much much
lower power state. If that is possible I can do it on our online servers to
save energy. The sever is Atom based platform with GMA 3150 graphics
integrated.
Thanks,
Joseph**
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