diff -urdN linux/drivers/char/hpet.c linux/drivers/char/hpet.c
--- linux/drivers/char/hpet.c	2005-10-08 16:26:51.000000000 +0200
+++ linux/drivers/char/hpet.c	2005-10-08 22:32:43.000000000 +0200
@@ -70,6 +70,7 @@
 	unsigned int hd_flags;
 	unsigned int hd_irq;
 	unsigned int hd_hdwirq;
+	int hd_levelirq;
 	char hd_name[HPET_DEV_NAME];
 };
 
@@ -120,6 +121,15 @@
 	unsigned long isr;
 
 	devp = data;
+	isr = (1 << (devp - devp->hd_hpets->hp_dev));
+	if (devp->hd_levelirq) {
+		unsigned long v;
+		
+		v = readl(&devp->hd_hpet->hpet_isr);
+		if (!(v & isr)) {
+			return IRQ_NONE;
+		}
+	}	
 
 	spin_lock(&hpet_lock);
 	devp->hd_irqdata++;
@@ -137,7 +147,7 @@
 			      &devp->hd_timer->hpet_compare);
 	}
 
-	isr = (1 << (devp - devp->hd_hpets->hp_dev));
+	/* Spec says that only 0 may be written to status bit when corresponding timer is in edge mode! */
 	writeq(isr, &devp->hd_hpet->hpet_isr);
 	spin_unlock(&hpet_lock);
 
@@ -351,6 +361,44 @@
 	return hpet_ioctl_common(devp, cmd, arg, 0);
 }
 
+static unsigned int hpet_find_irq(struct hpet_dev *devp)
+{
+	unsigned long long v;
+	unsigned int irqmask;
+	struct hpet_timer __iomem *timer;
+	unsigned int irq;
+	unsigned int hpet_id;
+
+	irq = devp->hd_hdwirq;
+	if (irq)
+		return irq;
+
+	hpet_id = devp - devp->hd_hpets->hp_dev;
+	timer = devp->hd_timer;
+	v = readq(&timer->hpet_config);
+	irq = (v & Tn_INT_ROUTE_CNF_MASK) >> Tn_INT_ROUTE_CNF_SHIFT;
+	irqmask = (v & Tn_INT_ROUTE_CAP_MASK) >> Tn_INI_ROUTE_CAP_SHIFT;
+	/* Try already assigned irq first?! */
+	for (irq = 0; irq < 32; irq++) {
+		int acpiirq = acpi_register_gsi(irq, ACPI_LEVEL_SENSITIVE, ACPI_ACTIVE_LOW);
+//		printk(KERN_ERR "Mapping %u => %u\n", irq, acpiirq);
+		/* Skip 0 (no such APIC pin), 2 (8254) and 8 (RTC) */
+		if (irq == 0 || irq == 2 || irq == 8)
+			continue;
+		if (can_request_irq(acpiirq, SA_INTERRUPT)) {
+			devp->hd_levelirq = 1;
+			v = (v & ~Tn_INT_ROUTE_CNF_MASK) | (irq << Tn_INT_ROUTE_CNF_SHIFT) | Tn_INT_TYPE_CNF_MASK;
+			writeq(v, &timer->hpet_config);
+			printk(KERN_DEBUG "hpet%u.%u: Reserved IRQ %u\n", devp->hd_hpets->hp_which, hpet_id, acpiirq);
+			return acpiirq;
+		} else {
+			printk(KERN_DEBUG "hpet%u.%u: IRQ %u is busy\n", devp->hd_hpets->hp_which, hpet_id, acpiirq);
+		}
+	}
+	printk(KERN_DEBUG "hpet%u.%u: No free IRQ found\n", devp->hd_hpets->hp_which, hpet_id);
+	return 0;
+}
+
 static int hpet_ioctl_ieon(struct hpet_dev *devp)
 {
 	struct hpet_timer __iomem *timer;
@@ -375,14 +422,14 @@
 	devp->hd_flags |= HPET_IE;
 	spin_unlock_irq(&hpet_lock);
 
 	t = readq(&timer->hpet_config);
-	irq = devp->hd_hdwirq;
+	irq = hpet_find_irq(devp);
 
 	if (irq) {
-		sprintf(devp->hd_name, "hpet%d", (int)(devp - hpetp->hp_dev));
+		sprintf(devp->hd_name, "hpet%d.%d", hpetp->hp_which, (int)(devp - hpetp->hp_dev));
 
 		if (request_irq
-		    (irq, hpet_interrupt, SA_INTERRUPT, devp->hd_name, (void *)devp)) {
+		    (irq, hpet_interrupt, (devp->hd_levelirq ? SA_SHIRQ : 0) | SA_INTERRUPT, devp->hd_name, (void *)devp)) {
 			printk(KERN_ERR "hpet: IRQ %d is not free\n", irq);
 			irq = 0;
 		}
@@ -477,8 +527,12 @@
 		{
 			struct hpet_info info;
 
-			info.hi_ireqfreq = hpet_time_div(hpetp->hp_period *
-							 devp->hd_ireqfreq);
+			if (devp->hd_ireqfreq)
+				info.hi_ireqfreq = hpet_time_div(hpetp->hp_period *
+								 devp->hd_ireqfreq);
+			else
+				info.hi_ireqfreq = ~0UL;
+
 			info.hi_flags =
 			    readq(&timer->hpet_config) & Tn_PER_INT_CAP_MASK;
 			info.hi_hpet = devp->hd_hpets->hp_which;
@@ -516,7 +570,7 @@
 			break;
 		}
 
-		if (arg & (arg - 1)) {
+		if (!arg) {
 			err = -EINVAL;
 			break;
 		}