Factor out AHCI enabling into ahci_enable_ahci() and enabling AHCI
before reading CAP in ahci_save_initial_config() as the spec requires
enabling AHCI mode before accessing any other registers.

Signed-off-by: Tejun Heo <[EMAIL PROTECTED]>
---
 drivers/ata/ahci.c |   27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

Index: work/drivers/ata/ahci.c
===================================================================
--- work.orig/drivers/ata/ahci.c
+++ work/drivers/ata/ahci.c
@@ -597,6 +597,20 @@ static inline void __iomem *ahci_port_ba
        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(str
        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.
         */
@@ -1042,13 +1059,10 @@ static int ahci_reset_controller(struct 
        /* 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 */
@@ -1067,8 +1081,7 @@ static int ahci_reset_controller(struct 
        }
 
        /* 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);
-
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