1 files changed, 6 insertions, 5 deletions

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index c611b3cbc67b..0fee5c66fd64 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -579,11 +579,12 @@ int __usb_get_extra_descriptor(char *buffer, unsigned size,
  * address (through the pointer provided).
  *
  * These buffers are used with URB_NO_xxx_DMA_MAP set in urb->transfer_flags
- * to avoid behaviors like using "DMA bounce buffers", or tying down I/O
- * mapping hardware for long idle periods.  The implementation varies between
+ * to avoid behaviors like using "DMA bounce buffers", or thrashing IOMMU
+ * hardware during URB completion/resubmit.  The implementation varies between
  * platforms, depending on details of how DMA will work to this device.
- * Using these buffers also helps prevent cacheline sharing problems on
- * architectures where CPU caches are not DMA-coherent.
+ * Using these buffers also eliminates cacheline sharing problems on
+ * architectures where CPU caches are not DMA-coherent.  On systems without
+ * bus-snooping caches, these buffers are uncached.
  *
  * When the buffer is no longer used, free it with usb_buffer_free().
  */
@@ -608,7 +609,7 @@ void *usb_buffer_alloc(
  *
  * This reclaims an I/O buffer, letting it be reused.  The memory must have
  * been allocated using usb_buffer_alloc(), and the parameters must match
- * those provided in that allocation request. 
+ * those provided in that allocation request.
  */
 void usb_buffer_free(
         struct usb_device *dev,