dual intel/rage xl with 1.5 xserver - how to get to work?

[Mike Ranweiler]

I'm trying to get a dual intel/mach64 setup working.  We have a system
with an onboard Intel and an ATI Rage XL in a PCI slot.  We're stuck
with the 1.5 X server to stay on a SLES base and with the Intel adapter
as the primary because of issues with intel-agp if it's set as the
secondary.

After some modification, the mach64 driver appears to initialize the
secondary, the LCD backlight comes on and the LCD info button will show
the H/V sync and resolution as set, but the video is junk.  There are no
errors in the logs that don't show up when the ATI adapter is the
primary adapter.  The default driver fails when it tries to do register
reads in ATIMach64Detect.

I got a suggestion to toggle the MEMORY and IO bits, similarly to what I
think xf86SetPciVideo used to do, amongst other things.  I toggle on and
then back off that in ATIPreInit, ATIMach64Sync, and ATIScreenInit.
Then I can get the screen up to at least come up, but the video is junk.
If I don't toggle the bits, but just set and leave them the driver works
fine, but then the Intel adapter doesn't.  Which makes sense.

I've looked, and as far as I can tell there is nothing PreInit that is
not covered (or that matters) with the toggling.  I didn't see anything
that was previously done outside of initialization sequence to handle
secondaries like this in the older scheme.

Are there any ideas on where I should look next?  Should I be looking
into the X server rather than just the driver?  Suggestions on where?
Are there other drivers doing this sort of things I should look at?

Thanks,

Mike

-- 
Mike Ranweiler