[libata] AHCI: enable AHCI mode, before using AHCI reset
AHCI spec says host-reset bit may only be set when the ahci-enable bit
is also set.
Noticed by Peer Chen <peerchen@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 9f3c591..b615390 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -827,8 +827,14 @@
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 */