Re: [MICROPATCH] Make x86_64 build work without GART_IOMMU

[corbet@lwn.net (Jonathan Corbet)]

> > "Nuts" means that the X server goes into an unkillable, 100% system time
> > state.  It manages to scribble a mess onto the screen first.  Pointer moves
> > (I believe that's in hardware) but the server does not respond to anything.
> 
> Most likely it is a problem with the AGP driver. I assume you have AGP 
> compiled in. Does it work when you boot with agp=off ? 

If you turn on CONFIG_GART_IOMMU, it seems to force CONFIG_AGP as well, so
yes.  And yes, if I boot with agp-off, it works.

Andrew had asked:

> There are various loops where the driver spins on a
> hardware register, with an mdelay() in the loop.
> 
> Can you get a sysrq-p trace?

There's this little problem in that, to make things go wrong, I have to
fire up X.  That pretty well hoses the display, and an attempt to chvt back
to a regular console just hangs.  I guess I may have to dig in and try to
track this one down the hard way; wish I knew more about AGP hardware...

Thanks,

jon