[Intel-gfx] Intel IVCH, Bug 49838

[Thomas Richter]

Hi Daniel, hi Ville,

as promised, I was recently able to borrow an X30 that - similar to the 
R31 - features the intel DVO VCH. As Ville mentioned, this notebook 
suffers from bug #49838, namely the screen is blank after a resume from 
suspend.

With some debugging, I was able to resolve this problem. The bug here is 
that the bios of the X30 apparently forgets to re-initialize the 
registers of the DVO; especially, the PLL remains uninitialized and the
panel output timing remains unitialized. No miracle the panel remains blank.

I added a bit of code that reads the registers of the DVO upon 
initialization (hopefully correctly installed by the DVO) and resets the 
DVO when installing a mode.

This fixes bug #49838.

I still have to cleanup the code and test the code on the R31 (which 
also sits here).

I have to travel a bit in the next days, so it's probably not going to 
be ready this week, but at least it is another 830-related bug resolved.

Greetings,
	Thomas