1 files changed, 27 insertions, 14 deletions

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 25f63f1096b4..b6bd05e3d439 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -18,9 +18,17 @@
 #include "hcd.h"	/* for usbcore internals */
 #include "usb.h"
 
+struct api_context {
+	struct completion	done;
+	int			status;
+};
+
 static void usb_api_blocking_completion(struct urb *urb)
 {
-	complete((struct completion *)urb->context);
+	struct api_context *ctx = urb->context;
+
+	ctx->status = urb->status;
+	complete(&ctx->done);
 }
 
 
@@ -32,20 +40,21 @@ static void usb_api_blocking_completion(struct urb *urb)
  */
 static int usb_start_wait_urb(struct urb *urb, int timeout, int *actual_length)
 { 
-	struct completion done;
+	struct api_context ctx;
 	unsigned long expire;
 	int retval;
-	int status = urb->status;
 
-	init_completion(&done); 	
-	urb->context = &done;
+	init_completion(&ctx.done);
+	urb->context = &ctx;
 	urb->actual_length = 0;
 	retval = usb_submit_urb(urb, GFP_NOIO);
 	if (unlikely(retval))
 		goto out;
 
 	expire = timeout ? msecs_to_jiffies(timeout) : MAX_SCHEDULE_TIMEOUT;
-	if (!wait_for_completion_timeout(&done, expire)) {
+	if (!wait_for_completion_timeout(&ctx.done, expire)) {
+		usb_kill_urb(urb);
+		retval = (ctx.status == -ENOENT ? -ETIMEDOUT : ctx.status);
 
 		dev_dbg(&urb->dev->dev,
 			"%s timed out on ep%d%s len=%d/%d\n",
@@ -54,11 +63,8 @@ static int usb_start_wait_urb(struct urb *urb, int timeout, int *actual_length)
 			usb_pipein(urb->pipe) ? "in" : "out",
 			urb->actual_length,
 			urb->transfer_buffer_length);
-
-		usb_kill_urb(urb);
-		retval = status == -ENOENT ? -ETIMEDOUT : status;
 	} else
-		retval = status;
+		retval = ctx.status;
 out:
 	if (actual_length)
 		*actual_length = urb->actual_length;
@@ -411,15 +417,22 @@ int usb_sg_init (
 		 * Some systems need to revert to PIO when DMA is temporarily
 		 * unavailable.  For their sakes, both transfer_buffer and
 		 * transfer_dma are set when possible.  However this can only
-		 * work on systems without HIGHMEM, since DMA buffers located
-		 * in high memory are not directly addressable by the CPU for
-		 * PIO ... so when HIGHMEM is in use, transfer_buffer is NULL
+		 * work on systems without:
+		 *
+		 *  - HIGHMEM, since DMA buffers located in high memory are
+		 *    not directly addressable by the CPU for PIO;
+		 *
+		 *  - IOMMU, since dma_map_sg() is allowed to use an IOMMU to
+		 *    make virtually discontiguous buffers be "dma-contiguous"
+		 *    so that PIO and DMA need diferent numbers of URBs.
+		 *
+		 * So when HIGHMEM or IOMMU are in use, transfer_buffer is NULL
 		 * to prevent stale pointers and to help spot bugs.
 		 */
 		if (dma) {
 			io->urbs [i]->transfer_dma = sg_dma_address (sg + i);
 			len = sg_dma_len (sg + i);
-#ifdef CONFIG_HIGHMEM
+#if defined(CONFIG_HIGHMEM) || defined(CONFIG_IOMMU)
 			io->urbs[i]->transfer_buffer = NULL;
 #else
 			io->urbs[i]->transfer_buffer =