libahci: Implement the capability to override the generic ahci interrupt handler.

This patch implements the capability to override the generic AHCI
interrupt handler so that specific ahci drivers can implement their
own custom interrupt handler routines.  It also exports
ahci_handle_port_intr so that custom irq_handler implementations can
use it.

tj: s/ahci_irq_handler/irq_handler/ and updated description.
Signed-off-by: Suman Tripathi <stripathi@apm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
(cherry picked from linux-next commit f070d671)
[ dannf: backported to v4.4 ]
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/ata/ahci.h

@@ -352,6 +352,7 @@ struct ahci_host_priv {
 	 * be overridden anytime before the host is activated.
 	 */
 	void			(*start_engine)(struct ata_port *ap);
+	irqreturn_t 		(*irq_handler)(int irq, void *dev_instance);
 };
 
 extern int ahci_ignore_sss;
@@ -400,6 +401,7 @@ int ahci_reset_em(struct ata_host *host);
 void ahci_print_info(struct ata_host *host, const char *scc_s);
 int ahci_host_activate(struct ata_host *host, struct scsi_host_template *sht);
 void ahci_error_handler(struct ata_port *ap);
+u32 ahci_handle_port_intr(struct ata_host *host, u32 irq_masked);
 
 static inline void __iomem *__ahci_port_base(struct ata_host *host,
 					     unsigned int port_no)

drivers/ata/libahci.c

@@ -112,6 +112,9 @@ static ssize_t ahci_store_em_buffer(struct device *dev,
 				    const char *buf, size_t size);
 static ssize_t ahci_show_em_supported(struct device *dev,
 				      struct device_attribute *attr, char *buf);
+static irqreturn_t ahci_single_edge_irq_intr(int irq, void *dev_instance);
+
+static irqreturn_t ahci_single_level_irq_intr(int irq, void *dev_instance);
 
 static DEVICE_ATTR(ahci_host_caps, S_IRUGO, ahci_show_host_caps, NULL);
 static DEVICE_ATTR(ahci_host_cap2, S_IRUGO, ahci_show_host_cap2, NULL);
@@ -511,6 +514,11 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
 
 	if (!hpriv->start_engine)
 		hpriv->start_engine = ahci_start_engine;
+
+	if (!hpriv->irq_handler)
+		hpriv->irq_handler = (hpriv->flags & AHCI_HFLAG_EDGE_IRQ) ?
+				     ahci_single_edge_irq_intr :
+				     ahci_single_level_irq_intr;
 }
 EXPORT_SYMBOL_GPL(ahci_save_initial_config);
 
@@ -1841,7 +1849,7 @@ static irqreturn_t ahci_multi_irqs_intr(int irq, void *dev_instance)
 	return IRQ_WAKE_THREAD;
 }
 
-static u32 ahci_handle_port_intr(struct ata_host *host, u32 irq_masked)
+u32 ahci_handle_port_intr(struct ata_host *host, u32 irq_masked)
 {
 	unsigned int i, handled = 0;
 
@@ -1867,6 +1875,7 @@ static u32 ahci_handle_port_intr(struct ata_host *host, u32 irq_masked)
 
 	return handled;
 }
+EXPORT_SYMBOL_GPL(ahci_handle_port_intr);
 
 static irqreturn_t ahci_single_edge_irq_intr(int irq, void *dev_instance)
 {
@@ -2528,14 +2537,18 @@ int ahci_host_activate(struct ata_host *host, struct scsi_host_template *sht)
 	int irq = hpriv->irq;
 	int rc;
 
-	if (hpriv->flags & AHCI_HFLAG_MULTI_MSI)
+	if (hpriv->flags & AHCI_HFLAG_MULTI_MSI) {
+		if (hpriv->irq_handler)
+			dev_warn(host->dev, "both AHCI_HFLAG_MULTI_MSI flag set \
+				 and custom irq handler implemented\n");
+
 		rc = ahci_host_activate_multi_irqs(host, irq, sht);
-	else if (hpriv->flags & AHCI_HFLAG_EDGE_IRQ)
-		rc = ata_host_activate(host, irq, ahci_single_edge_irq_intr,
-				       IRQF_SHARED, sht);
-	else
-		rc = ata_host_activate(host, irq, ahci_single_level_irq_intr,
+	} else {
+		rc = ata_host_activate(host, irq, hpriv->irq_handler,
 				       IRQF_SHARED, sht);
+	}
+
+
 	return rc;
 }
 EXPORT_SYMBOL_GPL(ahci_host_activate);