[PATCH] x86_64: Use function pointers to call DMA mapping functions

AK: I hacked Muli's original patch a lot and there were a lot
of changes - all bugs are probably to blame on me now.
There were also some changes in the fall back behaviour
for swiotlb - in particular it doesn't try to use GFP_DMA
now anymore. Also all DMA mapping operations use the
same core dma_alloc_coherent code with proper fallbacks now.
And various other changes and cleanups.

Known problems: iommu=force swiotlb=force together breaks
                needs more testing.

This patch cleans up x86_64's DMA mapping dispatching code. Right now
we have three possible IOMMU types: AGP GART, swiotlb and nommu, and
in the future we will also have Xen's x86_64 swiotlb and other HW
IOMMUs for x86_64. In order to support all of them cleanly, this
patch:

- introduces a struct dma_mapping_ops with function pointers for each
  of the DMA mapping operations of gart (AMD HW IOMMU), swiotlb
  (software IOMMU) and nommu (no IOMMU).

- gets rid of:

  if (swiotlb)
      return swiotlb_xxx();

- PCI_DMA_BUS_IS_PHYS is now checked against the dma_ops being set
This makes swiotlb faster by avoiding double copying in some cases.

Signed-Off-By: Muli Ben-Yehuda <mulix@mulix.org>
Signed-Off-By: Jon D. Mason <jdmason@us.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/arch/x86_64/kernel/pci-swiotlb.c b/arch/x86_64/kernel/pci-swiotlb.c
new file mode 100644
index 000000000000..3569a25ad7fb
--- /dev/null
+++ b/arch/x86_64/kernel/pci-swiotlb.c
@@ -0,0 +1,42 @@
+/* Glue code to lib/swiotlb.c */
+
+#include <linux/pci.h>
+#include <linux/cache.h>
+#include <linux/module.h>
+#include <asm/dma-mapping.h>
+#include <asm/proto.h>
+#include <asm/swiotlb.h>
+#include <asm/dma.h>
+
+int swiotlb __read_mostly;
+EXPORT_SYMBOL(swiotlb);
+
+struct dma_mapping_ops swiotlb_dma_ops = {
+        .mapping_error = swiotlb_dma_mapping_error,
+        .alloc_coherent = swiotlb_alloc_coherent,
+        .free_coherent = swiotlb_free_coherent,
+        .map_single = swiotlb_map_single,
+        .unmap_single = swiotlb_unmap_single,
+        .sync_single_for_cpu = swiotlb_sync_single_for_cpu,
+        .sync_single_for_device = swiotlb_sync_single_for_device,
+        .sync_single_range_for_cpu = swiotlb_sync_single_range_for_cpu,
+        .sync_single_range_for_device = swiotlb_sync_single_range_for_device,
+        .sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
+        .sync_sg_for_device = swiotlb_sync_sg_for_device,
+        .map_sg = swiotlb_map_sg,
+        .unmap_sg = swiotlb_unmap_sg,
+        .dma_supported = NULL,
+};
+
+void pci_swiotlb_init(void)
+{
+        /* don't initialize swiotlb if iommu=off (no_iommu=1) */
+        if (!iommu_aperture && !no_iommu &&
+            (end_pfn > MAX_DMA32_PFN || force_iommu))
+               swiotlb = 1;
+        if (swiotlb) {
+                swiotlb_init();
+                printk(KERN_INFO "PCI-DMA: Using software bounce buffering for IO (SWIOTLB)\n");
+                dma_ops = &swiotlb_dma_ops;
+        }
+}