diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 9f3c591c7214090f2cc4b5f17b921dd7de48f6c4..b615390b6b8a0fc7c52d4bc09060562f3f490a5c 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -827,8 +827,14 @@ static int ahci_reset_controller(struct ata_host *host)
 	void __iomem *mmio = host->iomap[AHCI_PCI_BAR];
 	u32 tmp;
 
-	/* global controller reset */
+	/* we must be in AHCI mode, before using anything
+	 * AHCI-specific, such as HOST_RESET.
+	 */
 	tmp = readl(mmio + HOST_CTL);
+	if (!(tmp & HOST_AHCI_EN))
+		writel(tmp | HOST_AHCI_EN, mmio + HOST_CTL);
+
+	/* global controller reset */
 	if ((tmp & HOST_RESET) == 0) {
 		writel(tmp | HOST_RESET, mmio + HOST_CTL);
 		readl(mmio + HOST_CTL); /* flush */