1 files changed, 29 insertions, 7 deletions

diff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c
index e795a7e2a38e..d51be7c7a2ef 100644
--- a/arch/powerpc/kernel/pci_64.c
+++ b/arch/powerpc/kernel/pci_64.c
@@ -21,13 +21,13 @@
 #include <linux/mm.h>
 #include <linux/list.h>
 #include <linux/syscalls.h>
+#include <linux/irq.h>
 
 #include <asm/processor.h>
 #include <asm/io.h>
 #include <asm/prom.h>
 #include <asm/pci-bridge.h>
 #include <asm/byteorder.h>
-#include <asm/irq.h>
 #include <asm/machdep.h>
 #include <asm/ppc-pci.h>
 
@@ -1254,15 +1254,37 @@ int pci_read_irq_line(struct pci_dev *pci_dev)
 
 	DBG("Try to map irq for %s...\n", pci_name(pci_dev));
 
+	/* Try to get a mapping from the device-tree */
 	if (of_irq_map_pci(pci_dev, &oirq)) {
-		DBG(" -> failed !\n");
-		return -1;
-	}
+		u8 line, pin;
+
+		/* If that fails, lets fallback to what is in the config
+		 * space and map that through the default controller. We
+		 * also set the type to level low since that's what PCI
+		 * interrupts are. If your platform does differently, then
+		 * either provide a proper interrupt tree or don't use this
+		 * function.
+		 */
+		if (pci_read_config_byte(pci_dev, PCI_INTERRUPT_PIN, &pin))
+			return -1;
+		if (pin == 0)
+			return -1;
+		if (pci_read_config_byte(pci_dev, PCI_INTERRUPT_LINE, &line) ||
+		    line == 0xff) {
+			return -1;
+		}
+		DBG(" -> no map ! Using irq line %d from PCI config\n", line);
 
-	DBG(" -> got one, spec %d cells (0x%08x...) on %s\n",
-	    oirq.size, oirq.specifier[0], oirq.controller->full_name);
+		virq = irq_create_mapping(NULL, line);
+		if (virq != NO_IRQ)
+			set_irq_type(virq, IRQ_TYPE_LEVEL_LOW);
+	} else {
+		DBG(" -> got one, spec %d cells (0x%08x...) on %s\n",
+		    oirq.size, oirq.specifier[0], oirq.controller->full_name);
 
-	virq = irq_create_of_mapping(oirq.controller, oirq.specifier, oirq.size);
+		virq = irq_create_of_mapping(oirq.controller, oirq.specifier,
+					     oirq.size);
+	}
 	if(virq == NO_IRQ) {
 		DBG(" -> failed to map !\n");
 		return -1;