Re: [PATCH 1/1] arm/dts: Tegra30: Add device tree support for SMMU

diff --git a/drivers/of/of_dma.c b/drivers/of/of_dma.c
new file mode 100644
index 0000000..1db1ccd
--- /dev/null
+++ b/drivers/of/of_dma.c

@@ -0,0 +1,35 @@
+/*
+ * Stealed from:

+ *	"arch/microblaze/kernel/prom_parse.c"
+ *	"arch/powerpc/kernel/prom_parse.c"
+ */
+
+#include <linux/of_address.h>
+
+void of_parse_dma_window(struct device_node *dn, const void *dma_window_prop,
+		unsigned long *busno, unsigned long *phys, unsigned long *size)
+{
+	const u32 *dma_window;

+	u32 cells;
+	const unsigned char *prop;
+
+	dma_window = dma_window_prop;
+
+	/* busno is always one cell */
+	if (busno)
+		*busno = *(dma_window++);

+
+	prop = of_get_property(dn, "#dma-address-cells", NULL);
+	if (!prop)
+		prop = of_get_property(dn, "#address-cells", NULL);
+
+	cells = prop ? *(u32 *)prop : of_n_addr_cells(dn);

+	*phys = of_read_number(dma_window, cells);
+
+	dma_window += cells;
+
+	prop = of_get_property(dn, "#dma-size-cells", NULL);
+	cells = prop ? *(u32 *)prop : of_n_size_cells(dn);