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

1 files changed, 8 insertions, 59 deletions

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index 48175e5bd001..97683e45ab04 100644
--- 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");