+#ifdef CONFIG_DMA_RESTRICTED_POOL
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/slab.h>
+#endif

I don't think any of this belongs into swiotlb.c.  Marking
swiotlb_init_io_tlb_mem non-static and having all this code in a separate
file is probably a better idea.

+#ifdef CONFIG_DMA_RESTRICTED_POOL
+static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
+				    struct device *dev)
+{
+	struct io_tlb_mem *mem = rmem->priv;
+	unsigned long nslabs = rmem->size >> IO_TLB_SHIFT;
+
+	if (dev->dma_io_tlb_mem)
+		return 0;
+
+	/* Since multiple devices can share the same pool, the private data,
+	 * io_tlb_mem struct, will be initialized by the first device attached
+	 * to it.
+	 */

This is not the normal kernel comment style.

+#ifdef CONFIG_ARM
+		if (!PageHighMem(pfn_to_page(PHYS_PFN(rmem->base)))) {
+			kfree(mem);
+			return -EINVAL;
+		}
+#endif /* CONFIG_ARM */

And this is weird.  Why would ARM have such a restriction?  And if we have
such rstrictions it absolutely belongs into an arch helper.

+		swiotlb_init_io_tlb_mem(mem, rmem->base, nslabs, false);
+
+		rmem->priv = mem;
+
+#ifdef CONFIG_DEBUG_FS
+		if (!debugfs_dir)
+			debugfs_dir = debugfs_create_dir("swiotlb", NULL);
+
+		swiotlb_create_debugfs(mem, rmem->name, debugfs_dir);

Doesn't the debugfs_create_dir belong into swiotlb_create_debugfs?  Also
please use IS_ENABLEd or a stub to avoid ifdefs like this.