1 files changed, 20 insertions, 7 deletions

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 49761bc12cf2..6f089b899a1a 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -597,6 +597,20 @@ static inline void __iomem *ahci_port_base(struct ata_port *ap)
         return __ahci_port_base(ap->host, ap->port_no);
 }
 
+static void ahci_enable_ahci(void __iomem *mmio)
+{
+        u32 tmp;
+
+        /* turn on AHCI_EN */
+        tmp = readl(mmio + HOST_CTL);
+        if (!(tmp & HOST_AHCI_EN)) {
+                tmp |= HOST_AHCI_EN;
+                writel(tmp, mmio + HOST_CTL);
+                tmp = readl(mmio + HOST_CTL);   /* flush && sanity check */
+                WARN_ON(!(tmp & HOST_AHCI_EN));
+        }
+}
+
 /**
  *      ahci_save_initial_config - Save and fixup initial config values
  *      @pdev: target PCI device
@@ -619,6 +633,9 @@ static void ahci_save_initial_config(struct pci_dev *pdev,
         u32 cap, port_map;
         int i;
 
+        /* make sure AHCI mode is enabled before accessing CAP */
+        ahci_enable_ahci(mmio);
+
         /* Values prefixed with saved_ are written back to host after
          * reset.  Values without are used for driver operation.
          */
@@ -1043,13 +1060,10 @@ static int ahci_reset_controller(struct ata_host *host)
         /* 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)) {
-                tmp |= HOST_AHCI_EN;
-                writel(tmp, mmio + HOST_CTL);
-        }
+        ahci_enable_ahci(mmio);
 
         /* global controller reset */
+        tmp = readl(mmio + HOST_CTL);
         if ((tmp & HOST_RESET) == 0) {
                 writel(tmp | HOST_RESET, mmio + HOST_CTL);
                 readl(mmio + HOST_CTL); /* flush */
@@ -1068,8 +1082,7 @@ static int ahci_reset_controller(struct ata_host *host)
         }
 
         /* turn on AHCI mode */
-        writel(HOST_AHCI_EN, mmio + HOST_CTL);
-        (void) readl(mmio + HOST_CTL);  /* flush */
+        ahci_enable_ahci(mmio);
 
         /* some registers might be cleared on reset.  restore initial values */
         ahci_restore_initial_config(host);