1 files changed, 100 insertions, 0 deletions
diff --git a/arch/x86/kernel/pci-nommu.c b/arch/x86/kernel/pci-nommu.c
new file mode 100644
index 00000000000..aec43d56f49
--- /dev/null
+++ b/arch/x86/kernel/pci-nommu.c
@@ -0,0 +1,100 @@
+/* Fallback functions when the main IOMMU code is not compiled in. This
+   code is roughly equivalent to i386. */
+#include <linux/mm.h>
+#include <linux/init.h>
+#include <linux/pci.h>
+#include <linux/string.h>
+#include <linux/dma-mapping.h>
+#include <linux/scatterlist.h>
+
+#include <asm/gart.h>
+#include <asm/processor.h>
+#include <asm/dma.h>
+
+static int
+check_addr(char *name, struct device *hwdev, dma_addr_t bus, size_t size)
+{
+	if (hwdev && bus + size > *hwdev->dma_mask) {
+		if (*hwdev->dma_mask >= DMA_32BIT_MASK)
+			printk(KERN_ERR
+			    "nommu_%s: overflow %Lx+%zu of device mask %Lx\n",
+				name, (long long)bus, size,
+				(long long)*hwdev->dma_mask);
+		return 0;
+	}
+	return 1;
+}
+
+static dma_addr_t
+nommu_map_single(struct device *hwdev, phys_addr_t paddr, size_t size,
+	       int direction)
+{
+	dma_addr_t bus = paddr;
+	WARN_ON(size == 0);
+	if (!check_addr("map_single", hwdev, bus, size))
+				return bad_dma_address;
+	flush_write_buffers();
+	return bus;
+}
+
+
+/* Map a set of buffers described by scatterlist in streaming
+ * mode for DMA.  This is the scatter-gather version of the
+ * above pci_map_single interface.  Here the scatter gather list
+ * elements are each tagged with the appropriate dma address
+ * and length.  They are obtained via sg_dma_{address,length}(SG).
+ *
+ * NOTE: An implementation may be able to use a smaller number of
+ *       DMA address/length pairs than there are SG table elements.
+ *       (for example via virtual mapping capabilities)
+ *       The routine returns the number of addr/length pairs actually
+ *       used, at most nents.
+ *
+ * Device ownership issues as mentioned above for pci_map_single are
+ * the same here.
+ */
+static int nommu_map_sg(struct device *hwdev, struct scatterlist *sg,
+	       int nents, int direction)
+{
+	struct scatterlist *s;
+	int i;
+
+	WARN_ON(nents == 0 || sg[0].length == 0);
+
+	for_each_sg(sg, s, nents, i) {
+		BUG_ON(!sg_page(s));
+		s->dma_address = sg_phys(s);
+		if (!check_addr("map_sg", hwdev, s->dma_address, s->length))
+			return 0;
+		s->dma_length = s->length;
+	}
+	flush_write_buffers();
+	return nents;
+}
+
+/* Make sure we keep the same behaviour */
+static int nommu_mapping_error(dma_addr_t dma_addr)
+{
+#ifdef CONFIG_X86_32
+	return 0;
+#else
+	return (dma_addr == bad_dma_address);
+#endif
+}
+
+
+const struct dma_mapping_ops nommu_dma_ops = {
+	.map_single = nommu_map_single,
+	.map_sg = nommu_map_sg,
+	.mapping_error = nommu_mapping_error,
+	.is_phys = 1,
+};
+
+void __init no_iommu_init(void)
+{
+	if (dma_ops)
+		return;
+
+	force_iommu = 0; /* no HW IOMMU */
+	dma_ops = &nommu_dma_ops;
+}