ahci: retry enabling AHCI a few times before spitting out WARN_ON()

Some chips need AHCI_EN set more than once to actually set it.  Try a
few times before giving up and spitting out WARN_ON().

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Peer Chen <pchen@nvidia.com>
Cc: Volker Armin Hemmann <volker.armin.hemmann@tu-clausthal.de>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 986e3324e3026230bee39dbf9b0001fe23c15c64..7c4f886f1f1635cc99911db1085f5630ac9ba77f 100644 (file)
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -556,16 +556,27 @@ static inline void __iomem *ahci_port_base(struct ata_port *ap)
 
 static void ahci_enable_ahci(void __iomem *mmio)
 {
+       int i;
        u32 tmp;
 
        /* turn on AHCI_EN */
        tmp = readl(mmio + HOST_CTL);
-       if (!(tmp & HOST_AHCI_EN)) {
+       if (tmp & HOST_AHCI_EN)
+               return;
+
+       /* Some controllers need AHCI_EN to be written multiple times.
+        * Try a few times before giving up.
+        */
+       for (i = 0; i < 5; i++) {
                tmp |= HOST_AHCI_EN;
                writel(tmp, mmio + HOST_CTL);
                tmp = readl(mmio + HOST_CTL);   /* flush && sanity check */
-               WARN_ON(!(tmp & HOST_AHCI_EN));
+               if (tmp & HOST_AHCI_EN)
+                       return;
+               msleep(10);
        }
+
+       WARN_ON(1);
 }
 
 /**