ahci: fix notification handling

Asynchronous notification on ICH9 didn't work because it didn't write
AN FIS into the RX area - it only updates SNotification.  Also,
snooping SDB_FIS RX area is racy against further SDB FIS receptions.
Let sata_async_notification() determine using SNTF if it's available
and snoop RX area iff SNTF isn't available

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 21 insertions, 9 deletions

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 6633c7422fc4..abfb72aae3de 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1420,6 +1420,7 @@ static void ahci_port_intr(struct ata_port *ap)
         void __iomem *port_mmio = ap->ioaddr.cmd_addr;
         struct ata_eh_info *ehi = &ap->link.eh_info;
         struct ahci_port_priv *pp = ap->private_data;
+        struct ahci_host_priv *hpriv = ap->host->private_data;
         u32 status, qc_active;
         int rc, known_irq = 0;
 
@@ -1432,17 +1433,28 @@ static void ahci_port_intr(struct ata_port *ap)
         }
 
         if (status & PORT_IRQ_SDB_FIS) {
-                /* If the 'N' bit in word 0 of the FIS is set, we just
-                 * received asynchronous notification.  Tell libata
-                 * about it.  Note that as the SDB FIS itself is
-                 * accessible, SNotification can be emulated by the
-                 * driver but don't bother for the time being.
+                /* If SNotification is available, leave notification
+                 * handling to sata_async_notification().  If not,
+                 * emulate it by snooping SDB FIS RX area.
+                 *
+                 * Snooping FIS RX area is probably cheaper than
+                 * poking SNotification but some constrollers which
+                 * implement SNotification, ICH9 for example, don't
+                 * store AN SDB FIS into receive area.
                  */
-                const __le32 *f = pp->rx_fis + RX_FIS_SDB;
-                u32 f0 = le32_to_cpu(f[0]);
-
-                if (f0 & (1 << 15))
+                if (hpriv->cap & HOST_CAP_SNTF)
                         sata_async_notification(ap);
+                else {
+                        /* If the 'N' bit in word 0 of the FIS is set,
+                         * we just received asynchronous notification.
+                         * Tell libata about it.
+                         */
+                        const __le32 *f = pp->rx_fis + RX_FIS_SDB;
+                        u32 f0 = le32_to_cpu(f[0]);
+
+                        if (f0 & (1 << 15))
+                                sata_async_notification(ap);
+                }
         }
 
         /* pp->active_link is valid iff any command is in flight */