AHCI: Do not read HOST_IRQ_STAT reg in multi-MSI mode

As described in AHCI v1.0 specification chapter 10.6.2.2
"Multiple MSI Based Messages" generation of interrupts
is not controlled through the HOST_IRQ_STAT register.

Considering MMIO access is expensive remove unnecessary
reading and writing of HOST_IRQ_STAT register.

Further, serializing access to the host data is no longer
needed and the interrupt service routine can avoid competing
on the host lock.

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Suggested-by: "Jiang, Dave" <dave.jiang@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: "Jiang, Dave" <dave.jiang@intel.com>
Cc: linux-ide@vger.kernel.org

diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index 6a22055..40f0e34 100644 (file)
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -304,7 +304,7 @@ struct ahci_port_priv {
        unsigned int            ncq_saw_d2h:1;
        unsigned int            ncq_saw_dmas:1;
        unsigned int            ncq_saw_sdb:1;
-       u32                     intr_status;    /* interrupts to handle */
+       atomic_t                intr_status;    /* interrupts to handle */
        spinlock_t              lock;           /* protects parent ata_port */
        u32                     intr_mask;      /* interrupts to enable */
        bool                    fbs_supported;  /* set iff FBS is supported */

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index 48175e5..97683e4 100644 (file)
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -1794,14 +1794,11 @@ static irqreturn_t ahci_port_thread_fn(int irq, void *dev_instance)
        struct ata_port *ap = dev_instance;
        struct ahci_port_priv *pp = ap->private_data;
        void __iomem *port_mmio = ahci_port_base(ap);
-       unsigned long flags;
        u32 status;
 
-       spin_lock_irqsave(&ap->host->lock, flags);
-       status = pp->intr_status;
-       if (status)
-               pp->intr_status = 0;
-       spin_unlock_irqrestore(&ap->host->lock, flags);
+       status = atomic_xchg(&pp->intr_status, 0);
+       if (!status)
+               return IRQ_NONE;
 
        spin_lock_bh(ap->lock);
        ahci_handle_port_interrupt(ap, port_mmio, status);
@@ -1810,67 +1807,19 @@ static irqreturn_t ahci_port_thread_fn(int irq, void *dev_instance)
        return IRQ_HANDLED;
 }
 
-static void ahci_update_intr_status(struct ata_port *ap)
+static irqreturn_t ahci_multi_irqs_intr(int irq, void *dev_instance)
 {
+       struct ata_port *ap = dev_instance;
        void __iomem *port_mmio = ahci_port_base(ap);
        struct ahci_port_priv *pp = ap->private_data;
        u32 status;
 
-       status = readl(port_mmio + PORT_IRQ_STAT);
-       writel(status, port_mmio + PORT_IRQ_STAT);
-
-       pp->intr_status |= status;
-}
-
-static irqreturn_t ahci_multi_irqs_intr(int irq, void *dev_instance)
-{
-       struct ata_port *ap_this = dev_instance;
-       struct ahci_port_priv *pp = ap_this->private_data;
-       struct ata_host *host = ap_this->host;
-       struct ahci_host_priv *hpriv = host->private_data;
-       void __iomem *mmio = hpriv->mmio;
-       unsigned int i;
-       u32 irq_stat, irq_masked;
-
        VPRINTK("ENTER\n");
 
-       spin_lock(&host->lock);
-
-       irq_stat = readl(mmio + HOST_IRQ_STAT);
-
-       if (!irq_stat) {
-               u32 status = pp->intr_status;
-
-               spin_unlock(&host->lock);
-
-               VPRINTK("EXIT\n");
-
-               return status ? IRQ_WAKE_THREAD : IRQ_NONE;
-       }
-
-       irq_masked = irq_stat & hpriv->port_map;
-
-       for (i = 0; i < host->n_ports; i++) {
-               struct ata_port *ap;
-
-               if (!(irq_masked & (1 << i)))
-                       continue;
-
-               ap = host->ports[i];
-               if (ap) {
-                       ahci_update_intr_status(ap);
-                       VPRINTK("port %u\n", i);
-               } else {
-                       VPRINTK("port %u (no irq)\n", i);
-                       if (ata_ratelimit())
-                               dev_warn(host->dev,
-                                        "interrupt on disabled port %u\n", i);
-               }
-       }
-
-       writel(irq_stat, mmio + HOST_IRQ_STAT);
+       status = readl(port_mmio + PORT_IRQ_STAT);
+       writel(status, port_mmio + PORT_IRQ_STAT);
 
-       spin_unlock(&host->lock);
+       atomic_or(status, &pp->intr_status);
 
        VPRINTK("EXIT\n");