Fan control for PowerMac7_3 (#3)

[Benjamin Herrenschmidt]

On Sat, 2004-10-16 at 15:32, H. Peter Anvin wrote:

> It's the backside fan that oscillates; backside_fan_pwm varies between 
> 30 and 100 in what is pretty much a squarewave.  See attached graph (and 
> note how the other fans vary with workload.)
> 
> I probably need to write a "power virus" program for the G5 to really 
> test out the high end (a power virus is a program which keeps the chip 
> running as hard as it can; generally keep all pipelines stuffed.)

think about also banging FPU and Altivec units then :)

Since it's low oscillation point is 30, I suppose it properly detects
U3H (can you verify that in the code, adding a printk for example in
init_backside_state()).

I'll double check the values used for the PID in darwin

Ben