preliminary 750GX PLL control patch

[Kevin Diggs]

Hi,

         I've attached a patch that adds preliminary access to the HID1 
register in the 750GX (aka the PLL config register). The patch is 
against 2.4.30. It has been lightly tested on a PowerMac 8600 with a 
PowerLogix PowerForce 750GX cpu card.

         Depending on the values for the pllx_cfg field, this should 
work on the 750FX as well ... except for the stuff in idle_6xx.S. Since 
there are plenty of people on this list way more smarterer than me I was 
hoping someone could answer a question about the powersave modes that 
some of the PowerPC processors have:

         Since, as I understand it, the clock is shut off to much of the 
chip when a powersave mode is engaged does it really buy you that much 
to switch to a lower clock speed? Wouldn't you be better off shutting 
off the unused PLL?

         Also, please note that I am not very experienced creating 
patches so please use a backup of your source tree.

                                         kevin

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