[PATCH] vgahw: Resurrect disabling of legacy VGA support

[Egbert Eich]

On Tue, Aug 13, 2013 at 04:57:55PM +0200, Mark Kettenis wrote:
> > Currently (at least on 49ee1c26ea982e) the idea seems to be that readST01 
> > is routed thru the PIO access path possibly for timing reasons. This will
> > however not work for PowerPC.
> 
> At least not without further fixes to libpciaccess and your kernel...

Looking thru the Xserver code as well libpciaccess everything seems to be in 
place to make this work. I have not looked thru the powerpc specific code
in the kernel to see if everything is inplace there.
It could well be that the reason why things MCed was that the VGA IOBase
was not initialized correctly.

> 
> Yes, this is the issue I was hinting at below.
> 
> > Moreover there's a bug in the libvgaHW so that IOBase does not get set
> > correctly at least for vgaHWSave/RestoreColormap(). This function would 
> > require the same logic as vgaHWSave/RestoreFonts().
> 
> Or rather make sure vgaHWGetIOBase() gets called by the nv driver.

Right. libvgahw seems to keep the IOBase setting well in sync to the
MiscOut register this this seems to be the most viable option.

I'm still contemplating about adding an assert function to libvgahw
to make sure the problem is noted.

> 
> I'll see if I can find some time to dust off my G5 iMac and figure out
> what's the best approach here.

I'd be curious if fixing the IOBase already takes care of the problem.
Will mail out the patches for the NV driver in a minute.

Cheers,
	Egbert.