Activate 5s watchdog timer in bcm kernel.

Reference: /n/sources/patch/applied/bcm-watchdog
Date: Wed Feb 20 15:40:15 CET 2013
Signed-off-by: miller@hamnavoe.com

--- /sys/src/9/bcm/archbcm.c	Wed Feb 20 15:39:21 2013
+++ /sys/src/9/bcm/archbcm.c	Wed Feb 20 15:39:19 2013
@@ -18,6 +18,7 @@
 
 enum {
 	Wdogfreq	= 65536,
+	Wdogtime	= 5,	/* seconds, ≤ 15 */
 };
 
 /*
@@ -28,6 +29,7 @@
 		Password	= 0x5A<<24,
 		CfgMask		= 0x03<<4,
 		CfgReset	= 0x02<<4,
+	Rsts		= 0x20>>2,
 	Wdog		= 0x24>>2,
 };
 
@@ -50,6 +52,25 @@
 		;
 }
 
+static void
+wdogfeed(void)
+{
+	u32int *r;
+
+	r = (u32int*)POWERREGS;
+	r[Wdog] = Password | (Wdogtime * Wdogfreq);
+	r[Rstc] = Password | (r[Rstc] & ~CfgMask) | CfgReset;
+}
+
+void
+wdogoff(void)
+{
+	u32int *r;
+
+	r = (u32int*)POWERREGS;
+	r[Rstc] = Password | (r[Rstc] & ~CfgMask);
+}
+	
 void
 cpuidprint(void)
 {
@@ -59,6 +80,7 @@
 void
 archbcmlink(void)
 {
+	addclock0link(wdogfeed, HZ);
 }
 
 int
--- /sys/src/9/bcm/clock.c	Wed Feb 20 15:39:24 2013
+++ /sys/src/9/bcm/clock.c	Wed Feb 20 15:39:22 2013
@@ -84,6 +84,7 @@
 
 	tm = (Armtimer*)ARMTIMER;
 	tm->ctl = 0;
+	wdogoff();
 }
 
 void
--- /sys/src/9/bcm/fns.h	Wed Feb 20 15:39:28 2013
+++ /sys/src/9/bcm/fns.h	Wed Feb 20 15:39:26 2013
@@ -73,6 +73,7 @@
 extern int userureg(Ureg*);
 extern void vectors(void);
 extern void vtable(void);
+extern void wdogoff(void);
 
 /*
  * floating point emulation