diff --git a/[refs] b/[refs]
index a7cce889823a..52e00ae1354e 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 17bb34a3c548c4fd2a7c859123a631f97c2af09f
+refs/heads/master: 4d4681f6b994baf93dff0e4f59ab4fe38b49ef13
diff --git a/trunk/drivers/scsi/libata-core.c b/trunk/drivers/scsi/libata-core.c
index 673ddf611d0e..c8d2201b126f 100644
--- a/trunk/drivers/scsi/libata-core.c
+++ b/trunk/drivers/scsi/libata-core.c
@@ -4202,14 +4202,17 @@ void ata_bmdma_setup(struct ata_queued_cmd *qc)
 
 void ata_bmdma_irq_clear(struct ata_port *ap)
 {
-    if (ap->flags & ATA_FLAG_MMIO) {
-        void __iomem *mmio = ((void __iomem *) ap->ioaddr.bmdma_addr) + ATA_DMA_STATUS;
-        writeb(readb(mmio), mmio);
-    } else {
-        unsigned long addr = ap->ioaddr.bmdma_addr + ATA_DMA_STATUS;
-        outb(inb(addr), addr);
-    }
+	if (!ap->ioaddr.bmdma_addr)
+		return;
 
+	if (ap->flags & ATA_FLAG_MMIO) {
+		void __iomem *mmio =
+		      ((void __iomem *) ap->ioaddr.bmdma_addr) + ATA_DMA_STATUS;
+		writeb(readb(mmio), mmio);
+	} else {
+		unsigned long addr = ap->ioaddr.bmdma_addr + ATA_DMA_STATUS;
+		outb(inb(addr), addr);
+	}
 }