libata: add ata_ratelimit(), use it in AHCI driver irq handler

drivers/scsi/ahci.c

@@ -672,17 +672,36 @@ static irqreturn_t ahci_interrupt (int irq, void *dev_instance, struct pt_regs *
 
         for (i = 0; i < host_set->n_ports; i++) {
 		struct ata_port *ap;
-		u32 tmp;
 
-		VPRINTK("port %u\n", i);
+		if (!(irq_stat & (1 << i)))
+			continue;
+
 		ap = host_set->ports[i];
-		tmp = irq_stat & (1 << i);
-		if (tmp && ap) {
+		if (ap) {
 			struct ata_queued_cmd *qc;
 			qc = ata_qc_from_tag(ap, ap->active_tag);
-			if (ahci_host_intr(ap, qc))
-				irq_ack |= (1 << i);
+			if (!ahci_host_intr(ap, qc))
+				if (ata_ratelimit()) {
+					struct pci_dev *pdev =
+					  to_pci_dev(ap->host_set->dev);
+					printk(KERN_WARNING
+					  "ahci(%s): unhandled interrupt on port %u\n",
+					  pci_name(pdev), i);
+				}
+
+			VPRINTK("port %u\n", i);
+		} else {
+			VPRINTK("port %u (no irq)\n", i);
+			if (ata_ratelimit()) {
+				struct pci_dev *pdev =
+				  to_pci_dev(ap->host_set->dev);
+				printk(KERN_WARNING
+				  "ahci(%s): interrupt on disabled port %u\n",
+				  pci_name(pdev), i);
+			}
 		}
+
+		irq_ack |= (1 << i);
 	}
 
 	if (irq_ack) {

drivers/scsi/libata-core.c

@@ -48,6 +48,7 @@
 #include <linux/completion.h>
 #include <linux/suspend.h>
 #include <linux/workqueue.h>
+#include <linux/jiffies.h>
 #include <scsi/scsi.h>
 #include "scsi.h"
 #include "scsi_priv.h"
@@ -4688,6 +4689,27 @@ static void __exit ata_exit(void)
 module_init(ata_init);
 module_exit(ata_exit);
 
+static unsigned long ratelimit_time;
+static spinlock_t ata_ratelimit_lock = SPIN_LOCK_UNLOCKED;
+
+int ata_ratelimit(void)
+{
+	int rc;
+	unsigned long flags;
+
+	spin_lock_irqsave(&ata_ratelimit_lock, flags);
+
+	if (time_after(jiffies, ratelimit_time)) {
+		rc = 1;
+		ratelimit_time = jiffies + (HZ/5);
+	} else
+		rc = 0;
+
+	spin_unlock_irqrestore(&ata_ratelimit_lock, flags);
+
+	return rc;
+}
+
 /*
  * libata is essentially a library of internal helper functions for
  * low-level ATA host controller drivers.  As such, the API/ABI is
@@ -4729,6 +4751,7 @@ EXPORT_SYMBOL_GPL(sata_phy_reset);
 EXPORT_SYMBOL_GPL(__sata_phy_reset);
 EXPORT_SYMBOL_GPL(ata_bus_reset);
 EXPORT_SYMBOL_GPL(ata_port_disable);
+EXPORT_SYMBOL_GPL(ata_ratelimit);
 EXPORT_SYMBOL_GPL(ata_scsi_ioctl);
 EXPORT_SYMBOL_GPL(ata_scsi_queuecmd);
 EXPORT_SYMBOL_GPL(ata_scsi_error);

include/linux/libata.h

@@ -410,6 +410,8 @@ extern int ata_scsi_queuecmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmn
 extern int ata_scsi_error(struct Scsi_Host *host);
 extern int ata_scsi_release(struct Scsi_Host *host);
 extern unsigned int ata_host_intr(struct ata_port *ap, struct ata_queued_cmd *qc);
+extern int ata_ratelimit(void);
+
 /*
  * Default driver ops implementations
  */