From: Alan Cox <alan@lxorguk.ukuu.org.uk>

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


diff -puN drivers/ata/pata_atiixp.c~pata_atiixp-audit-notes-on-locking drivers/ata/pata_atiixp.c
--- a/drivers/ata/pata_atiixp.c~pata_atiixp-audit-notes-on-locking
+++ a/drivers/ata/pata_atiixp.c
@@ -173,6 +173,9 @@ static void atiixp_set_dmamode(struct at
  *
  *	When DMA begins we need to ensure that the UDMA control
  *	register for the channel is correctly set.
+ *
+ *	Note: The host lock held by the libata layer protects
+ *	us from two channels both trying to set DMA bits at once
  */
 
 static void atiixp_bmdma_start(struct ata_queued_cmd *qc)
@@ -199,6 +202,9 @@ static void atiixp_bmdma_start(struct at
  *
  *	DMA has completed. Clear the UDMA flag as the next operations will
  *	be PIO ones not UDMA data transfer.
+ *
+ *	Note: The host lock held by the libata layer protects
+ *	us from two channels both trying to set DMA bits at once
  */
 
 static void atiixp_bmdma_stop(struct ata_queued_cmd *qc)
_