iTCO_wdt: fix TCO V1 timeout values and limits

For TCO V1 devices the programmed timeout was twice too long
because the fact that the TCO V1 timer needs to count down
twice before triggering the watchdog, wasn't accounted for.
Also the timeout values in the module description and error
message were clarified.

Signed-off-by: Pádraig Brady <P@draigBrady.com>
Tested-by: Simon Kagstrom <simon.kagstrom@netinsight.se>

--- a/iTCO_wdt.c	2010-04-06 15:00:41.000000000 +0000
+++ b/iTCO_wdt.c	2010-04-07 16:08:27.000000000 +0000
@@ -391,8 +391,8 @@
 #define WATCHDOG_HEARTBEAT 30	/* 30 sec default heartbeat */
 static int heartbeat = WATCHDOG_HEARTBEAT;  /* in seconds */
 module_param(heartbeat, int, 0);
-MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. "
-	"(2<heartbeat<39 (TCO v1) or 613 (TCO v2), default="
+MODULE_PARM_DESC(heartbeat, "Watchdog timeout in seconds. "
+	"5..76 (TCO v1) or 3..614 (TCO v2), default="
 				__MODULE_STRING(WATCHDOG_HEARTBEAT) ")");
 
 static int nowayout = WATCHDOG_NOWAYOUT;
@@ -408,8 +408,12 @@
 static inline unsigned int seconds_to_ticks(int seconds)
 {
 	/* the internal timer is stored as ticks which decrement
-	 * every 0.6 seconds */
-	return (seconds * 10) / 6;
+	 * every 0.6 seconds. For TCO v1 the timer counts down
+	 * twice before triggering the watchdog */
+	if (iTCO_wdt_private.iTCO_version == 1)
+		return (seconds * 5) / 6;
+	else
+		return (seconds * 10) / 6;
 }
 
 static void iTCO_wdt_set_NO_REBOOT_bit(void)
@@ -521,10 +525,15 @@
 	iTCO_vendor_pre_keepalive(iTCO_wdt_private.ACPIBASE, heartbeat);
 
 	/* Reload the timer by writing to the TCO Timer Counter register */
-	if (iTCO_wdt_private.iTCO_version == 2)
-		outw(0x01, TCO_RLD);
-	else if (iTCO_wdt_private.iTCO_version == 1)
+	if (iTCO_wdt_private.iTCO_version == 1) {
+		/* Reset the timeout status bit so that the timer
+		 * needs to count down twice again before rebooting */
+		outb (0x08, TCO1_STS); /* write 1 to clear bit */
+
 		outb(0x01, TCO_RLD);
+	} else if (iTCO_wdt_private.iTCO_version == 2) {
+		outw(0x01, TCO_RLD);
+	}
 
 	spin_unlock(&iTCO_wdt_private.io_lock);
 	return 0;
@@ -842,10 +851,16 @@
 	/* Check that the heartbeat value is within it's range;
 	   if not reset to the default */
 	if (iTCO_wdt_set_heartbeat(heartbeat)) {
-		iTCO_wdt_set_heartbeat(WATCHDOG_HEARTBEAT);
+		int tco_min=5; int tco_max=76; /* TCO V1 */
+		if (iTCO_wdt_private.iTCO_version == 2) {
+			tco_min=3; tco_max=614;
+		}
 		printk(KERN_INFO PFX
-			"heartbeat value must be 2 < heartbeat < 39 (TCO v1) "
-				"or 613 (TCO v2), using %d\n", heartbeat);
+			"timeout value %d is not between %d and %d"
+			" inclusive, using %d\n",
+			heartbeat, tco_min, tco_max, WATCHDOG_HEARTBEAT);
+
+		iTCO_wdt_set_heartbeat(WATCHDOG_HEARTBEAT);
 	}
 
 	ret = misc_register(&iTCO_wdt_miscdev);