Subject: Re: AGPGART driver for ArticiaS - ioremap() problem

From: "Gerhard Pircher" <[email-masked]>
Date: Wed, 18 Jan 2006 20:40:54 +0100 (MET)

> > That's the problem: we don't have the datasheet for the ArticiaS. :-( 
> > But the driver initializes correctly with the Uninorth code now and
> > with the DRI/DRM code changed. (The code in drm_vm.c checks for Apple's
> > PCI vendor ID. Therefore I just added a check for MAI's PCI vendor ID.)
> > But the X server freezes after the login screen is displayed (IIRC the
> > mouse still works, but the keyboard is dead!?).
> 
> That check is only necessary because Apple bridge puts the AGP aperture
> at bus address 0. This is probably not the case for you. You may not
> have that right. Check what you put in agp_bridge->gart_bus_addr
Hmm, I'm not sure what value agp_bridge->gart_bus_addr should have. The BIOS
doesn't setup it and the VIA AGPGART driver even reads it out from the
northbridge's registers! Where does the value for agp_bridge->gart_bus_addr
come from? For now it is set to 0x0, which would require the modification in
drm_vm.c!?

> > >  - The AGP aperture itself. The main issue there is wether your
> > > chipset makes the AGP aperture visible to the CPU or not. The Apple
> > > UniNorth one doesn't for example, it;'s only visible to the graphic
> > > chip. That is why the uninorth driver sets cant_use_aperture to 1.
> > > That forces the DRM to generate AGP mappings by using the real memory 
> > > pages and putting them together into a virtual mapping instead of
> > > doing a direct mapping of the AGP aperture on the bus. Most x86
> > > chipsets however _can_, thus a simple remapping of pages is enough.
> 
> > Good question! How would I have to modify the Uninorth driver to use a
> > direct mapping of the AGP aperture on the bus?
> 
> Don't set cant_use_aperture to 1 :)
:) The driver seems to work better with cant_use_aperture set to 1, so I
leave it as it is. BTW: What's the meaning of needs_scratch_page?

Thanks for your support!

Gerhard

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