1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/ide/sis5513.c b/drivers/ide/sis5513.c
index afca22beaadf..3b88eba04c9c 100644
--- a/drivers/ide/sis5513.c
+++ b/drivers/ide/sis5513.c
@@ -2,7 +2,7 @@
  * Copyright (C) 1999-2000      Andre Hedrick <andre@linux-ide.org>
  * Copyright (C) 2002           Lionel Bouton <Lionel.Bouton@inet6.fr>, Maintainer
  * Copyright (C) 2003           Vojtech Pavlik <vojtech@suse.cz>
- * Copyright (C) 2007           Bartlomiej Zolnierkiewicz
+ * Copyright (C) 2007-2009      Bartlomiej Zolnierkiewicz
  *
  * May be copied or modified under the terms of the GNU General Public License
  *
@@ -281,11 +281,13 @@ static void config_drive_art_rwp(ide_drive_t *drive)
 
         pci_read_config_byte(dev, 0x4b, &reg4bh);
 
+        rw_prefetch = reg4bh & ~(0x11 << drive->dn);
+
         if (drive->media == ide_disk)
-                rw_prefetch = 0x11 << drive->dn;
+                rw_prefetch |= 0x11 << drive->dn;
 
-        if ((reg4bh & (0x11 << drive->dn)) != rw_prefetch)
-                pci_write_config_byte(dev, 0x4b, reg4bh|rw_prefetch);
+        if (reg4bh != rw_prefetch)
+                pci_write_config_byte(dev, 0x4b, rw_prefetch);
 }
 
 static void sis_set_pio_mode(ide_drive_t *drive, const u8 pio)