finally fix intr routing on alphas such as the as500 after months of

breakage:

- call PCIB_ROUTE_INTERRUPT() regardless of how valid the intline looks.
  Some alphas leave garbage in the intline and leave the intr mapping
  to OS platform support routines that map slots/buses to intlines
- Down in the alpha pci code, first try platform.pci_intr_route() and
  if it doesn't exist or returns garbage, just read the intline out of
  config space.

tested on AS500 (garbage in intline) and UP1000 (PC-like, intline is valid)

Note that a nice little hack like the APIC_IO section of pci_cfgregread()
is not workable.  This is because the calling interface for
alpha_pci_route_interrupt() requires us to figure out the bus/slot/etc
from a device_t.  At pci_read_device() time, we don't have a device_t
for the bus/slot/func in question.

sys/alpha/pci/pcibus.c

@@ -40,6 +40,7 @@
 #include <sys/sysctl.h>
 #include <sys/rman.h>
 
+#include <pci/pcireg.h>
 #include <pci/pcivar.h>
 #include <machine/chipset.h>
 #include <machine/cpuconf.h>
@@ -80,6 +81,8 @@ SYSCTL_LONG(_hw_chipset, OID_AUTO, hae_mask, CTLFLAG_RD, &chipset_hae_mask, 0,
 int
 alpha_pci_route_interrupt(device_t bus, device_t dev, int pin)
 {
+	int intline = 255;
+
 	/*
 	 * Validate requested pin number.
 	 */
@@ -87,8 +90,10 @@ alpha_pci_route_interrupt(device_t bus, device_t dev, int pin)
 		return(255);
 	
 	if (platform.pci_intr_route)
-		return(platform.pci_intr_route(bus, dev, pin));
-	return(255);
+		intline = platform.pci_intr_route(bus, dev, pin);
+	if (intline == 255)
+		intline = pci_read_config(dev, PCIR_INTLINE, 1);
+	return intline;
 }
 
 #ifdef DEV_ISA

sys/dev/pci/pci.c

@@ -1207,7 +1207,11 @@ pci_alloc_resource(device_t dev, device_t child, int type, int *rid,
 		 * If device doesn't have an interrupt routed, and is deserving of 
 		 * an interrupt, try to assign it one.
 		 */
-		if ((type == SYS_RES_IRQ) && (cfg->intline == 255) && (cfg->intpin != 0)) {
+		if ((type == SYS_RES_IRQ) 
+#ifndef __alpha__
+			&& (cfg->intline == 255) && (cfg->intpin != 0)
+#endif
+									) {
 			cfg->intline = PCIB_ROUTE_INTERRUPT(device_get_parent(dev), child,
 							    cfg->intpin);
 			if (cfg->intline != 255) {