[BUG/RFC/PATCH] drm: Fix for non-coherent DMA PowerPC

[Benjamin Herrenschmidt]

> Xorg (v7.1.1, Debian Etch) crashes with this patch (applied to 2.6.25-rc3)
> on my AmigaOne with a Radeon 9200 (PCIGART mode enabled). See the attached
> log file for the stack trace.

That doesn't look possible, which is weird... looks like we are passing
0 to clean_dcache_range().

Interestingly enough, I can -see- possible issues with the ppc32 DMA API
when trying to use HIGHMEM but that isn't the case here... 

Can you add printk's to ati_pcigart.c to print the arguments passed to

+               dma_sync_single_for_device(&dev->pdev->dev,
+                                          bus_address,
+                                          max_pages * sizeof(u32),
+                                          PCI_DMA_TODEVICE);
+

And also print the result of bus_to_virt(bus_address) ?

Ben.