diff --git a/arch/parisc/include/asm/parisc-device.h b/arch/parisc/include/asm/parisc-device.h
index 9afdad6..eaf4dc1 100644
--- a/arch/parisc/include/asm/parisc-device.h
+++ b/arch/parisc/include/asm/parisc-device.h
@@ -23,6 +23,7 @@
 	/* generic info returned from pdc_pat_cell_module() */
 	unsigned long	mod_info;	/* PAT specific - Misc Module info */
 	unsigned long	pmod_loc;	/* physical Module location */
+	unsigned long	mod0;
 #endif
 	u64		dma_mask;	/* DMA mask for I/O */
 	struct device 	dev;
@@ -61,4 +62,6 @@
 
 extern struct bus_type parisc_bus_type;
 
+int iosapic_serial_irq(struct parisc_device *dev);
+
 #endif /*_ASM_PARISC_PARISC_DEVICE_H_*/
diff --git a/arch/parisc/kernel/inventory.c b/arch/parisc/kernel/inventory.c
index 3295ef4..f0b6722 100644
--- a/arch/parisc/kernel/inventory.c
+++ b/arch/parisc/kernel/inventory.c
@@ -211,6 +211,7 @@
 	/* REVISIT: who is the consumer of this? not sure yet... */
 	dev->mod_info = pa_pdc_cell->mod_info;	/* pass to PAT_GET_ENTITY() */
 	dev->pmod_loc = pa_pdc_cell->mod_location;
+	dev->mod0 = pa_pdc_cell->mod[0];
 
 	register_parisc_device(dev);	/* advertise device */
 
diff --git a/drivers/parisc/iosapic.c b/drivers/parisc/iosapic.c
index e79e006..9ee04b4 100644
--- a/drivers/parisc/iosapic.c
+++ b/drivers/parisc/iosapic.c
@@ -811,18 +811,28 @@
 	return pcidev->irq;
 }
 
-static struct iosapic_info *first_isi = NULL;
+static struct iosapic_info *iosapic_list;
 
 #ifdef CONFIG_64BIT
-int iosapic_serial_irq(int num)
+int iosapic_serial_irq(struct parisc_device *dev)
 {
-	struct iosapic_info *isi = first_isi;
-	struct irt_entry *irte = NULL;  /* only used if PAT PDC */
+	struct iosapic_info *isi;
+	struct irt_entry *irte;
 	struct vector_info *vi;
-	int isi_line;	/* line used by device */
+	int cnt;
+	int intin;
+
+	intin = (dev->mod_info >> 24) & 15;
 
 	/* lookup IRT entry for isi/slot/pin set */
-	irte = &irt_cell[num];
+	for (cnt = 0; cnt < irt_num_entry; cnt++) {
+		irte = &irt_cell[cnt];
+		if (COMPARE_IRTE_ADDR(irte, dev->mod0) &&
+		    irte->dest_iosapic_intin == intin)
+			break;
+	}
+	if (cnt >= irt_num_entry)
+		return 0; /* no irq found, force polling */
 
 	DBG_IRT("iosapic_serial_irq(): irte %p %x %x %x %x %x %x %x %x\n",
 		irte,
@@ -834,11 +844,17 @@
 		irte->src_seg_id,
 		irte->dest_iosapic_intin,
 		(u32) irte->dest_iosapic_addr);
-	isi_line = irte->dest_iosapic_intin;
+
+	/* search for iosapic */
+	for (isi = iosapic_list; isi; isi = isi->isi_next)
+		if (isi->isi_hpa == dev->mod0)
+			break;
+	if (!isi)
+		return 0; /* no iosapic found, force polling */
 
 	/* get vector info for this input line */
-	vi = isi->isi_vector + isi_line;
-	DBG_IRT("iosapic_serial_irq:  line %d vi 0x%p\n", isi_line, vi);
+	vi = isi->isi_vector + intin;
+	DBG_IRT("iosapic_serial_irq:  line %d vi 0x%p\n", iosapic_intin, vi);
 
 	/* If this IRQ line has already been setup, skip it */
 	if (vi->irte)
@@ -941,8 +957,8 @@
 		vip->irqline = (unsigned char) cnt;
 		vip->iosapic = isi;
 	}
-	if (!first_isi)
-		first_isi = isi;
+	isi->isi_next = iosapic_list;
+	iosapic_list = isi;
 	return isi;
 }
 
diff --git a/drivers/tty/serial/8250/8250_gsc.c b/drivers/tty/serial/8250/8250_gsc.c
index bb91b47..2e3ea1a 100644
--- a/drivers/tty/serial/8250/8250_gsc.c
+++ b/drivers/tty/serial/8250/8250_gsc.c
@@ -31,9 +31,8 @@
 	int err;
 
 #ifdef CONFIG_64BIT
-	extern int iosapic_serial_irq(int cellnum);
 	if (!dev->irq && (dev->id.sversion == 0xad))
-		dev->irq = iosapic_serial_irq(dev->mod_index-1);
+		dev->irq = iosapic_serial_irq(dev);
 #endif
 
 	if (!dev->irq) {