Re: [Dri-devel] PPC Lockup (ati-pcigart-branch)

Hi,

On Mon, 22 Jan 2001, Jeff Hartmann wrote:

Later on this list of pages will be mapped into user space by the DRM's
mmap routine.  It uses vma_nopage to accomplish this.  vma_nopage
functions should return struct page *, we do this by returning
pagelist[page_offset_in_pages_from_start_of_vma].  This should work on
fine on any arch's kernel.  We haven't gotten to this point in the code
yet, so its not the issue we are addressing.

Do you make the page private already?

Another thing that happens later is that we need the bus address of each
of these pages to program the card to do scatter gather dma from this
region.  We do virt_to_bus(pagelist[i]->virtual) to accomplish this
translation.

Better use page_address() to get the virtual address and then use
pci_map_single() or pci_map_sg() to get a dma address.

I know on the ia32 a pgd/pmd can actually point to 4MB pages rather then
a real pte.  Does the PowerPC have anything like this?  I would doubt
that I would encounter anything like this from a vmalloc'ed area of
memory (since vmalloc is arch independent and it would call alloc_page
for each individual pte.)  Am I correct in this assumption?

ppc doesn't have page table, it either uses a hash table or the tlb
entries have to be filled by software. Anyway, pgd/pmd/pte are used to
keep the management compatible to Linux and are like ia32 also two levels.

Another thing we might be running into here is that vmalloc does not
guarantee a virtually contiguous area of memory (or so I am told.)  I've
NEVER seen this in practice on an ia32 platform.  Does this happen only
happen on other platforms, or perhaps happen more often on other platforms?

Someone was confused :). vmalloc can't guarantee that it allocates a
physical contiguous area.

bye, Roman


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