commit 6bd09032a496354cf7aec0142e36ab92c96bda8e
Author: Piotr Ziecik <kosmo@semihalf.com>
Date:   Wed Jun 17 10:40:40 2009 +0200

    usb: Fix cache flush/invalidate operation.
    
    USB stack implements cache flush and invalidate operations
    as bus_dma sychronization. However used synchronization flags
    does not caused required cache operation on all architectures.
    
    This patch fixes this problem passing correct flags to bus_dmamap_sync()
    function.

diff --git a/sys/dev/usb/usb_busdma.c b/sys/dev/usb/usb_busdma.c
index 3d6a5be..69a6fff 100644
--- a/sys/dev/usb/usb_busdma.c
+++ b/sys/dev/usb/usb_busdma.c
@@ -658,8 +658,7 @@ usb_pc_cpu_invalidate(struct usb_page_cache *pc)
 		/* nothing has been loaded into this page cache! */
 		return;
 	}
-	bus_dmamap_sync(pc->tag, pc->map,
-	    BUS_DMASYNC_POSTWRITE | BUS_DMASYNC_POSTREAD);
+	bus_dmamap_sync(pc->tag, pc->map, BUS_DMASYNC_PREREAD);
 }
 
 /*------------------------------------------------------------------------*
@@ -672,8 +671,7 @@ usb_pc_cpu_flush(struct usb_page_cache *pc)
 		/* nothing has been loaded into this page cache! */
 		return;
 	}
-	bus_dmamap_sync(pc->tag, pc->map,
-	    BUS_DMASYNC_PREWRITE | BUS_DMASYNC_PREREAD);
+	bus_dmamap_sync(pc->tag, pc->map, BUS_DMASYNC_PREWRITE);
 }
 
 /*------------------------------------------------------------------------*