Re: alpha iommu fixes

[Richard Henderson]

On Mon, May 21, 2001 at 03:51:51PM +0400, Ivan Kokshaysky wrote:
> I'm unable reproduce it with *8Mb* window, so I'm asking.

Me either.  But Tom Vier, the guy who started this thread
was able to use up the 8MB.  Which is completely believable.

The following should aleviate the situation on these smaller
machines where the direct map does cover all physical memory.
Really, we were failing gratuitously before.

On Tsunami and Titan, espectially with more than 4G ram we
should probably just go ahead and allocate the 512M or 1G
scatter-gather arena.

(BTW, Andrea, it's easy enough to work around the Cypress
problem by marking the last 1M of the 1G arena in use.)

r~

diff -ruNp linux/arch/alpha/kernel/pci_iommu.c linux-new/arch/alpha/kernel/pci_iommu.c
--- linux/arch/alpha/kernel/pci_iommu.c	Fri Mar  2 11:12:07 2001
+++ linux-new/arch/alpha/kernel/pci_iommu.c	Mon May 21 01:25:25 2001
@@ -402,8 +402,20 @@ sg_fill(struct scatterlist *leader, stru
 	paddr &= ~PAGE_MASK;
 	npages = calc_npages(paddr + size);
 	dma_ofs = iommu_arena_alloc(arena, npages);
-	if (dma_ofs < 0)
-		return -1;
+	if (dma_ofs < 0) {
+		/* If we attempted a direct map above but failed, die.  */
+		if (leader->dma_address == 0)
+			return -1;
+
+		/* Otherwise, break up the remaining virtually contiguous
+		   hunks into individual direct maps.  */
+		for (sg = leader; sg < end; ++sg)
+			if (sg->dma_address == 2 || sg->dma_address == -2)
+				sg->dma_address = 0;
+
+		/* Retry.  */
+		return sg_fill(leader, end, out, arena, max_dma);
+	}
 
 	out->dma_address = arena->dma_base + dma_ofs*PAGE_SIZE + paddr;
 	out->dma_length = size;