i386: PIT stop only, when in periodic or oneshot mode

The patch is necessary on one of my boxen, where programming the stop
sequence twice leads to PIT malfunction.

Sigh !
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/i386/kernel/i8253.c

@@ -47,9 +47,12 @@ static void init_pit_timer(enum clock_event_mode mode,
 
 	case CLOCK_EVT_MODE_SHUTDOWN:
 	case CLOCK_EVT_MODE_UNUSED:
-		outb_p(0x30, PIT_MODE);
-		outb_p(0, PIT_CH0);	/* LSB */
-		outb_p(0, PIT_CH0);	/* MSB */
+		if (evt->mode == CLOCK_EVT_MODE_PERIODIC ||
+		    evt->mode == CLOCK_EVT_MODE_ONESHOT) {
+			outb_p(0x30, PIT_MODE);
+			outb_p(0, PIT_CH0);
+			outb_p(0, PIT_CH0);
+		}
 		break;
 
 	case CLOCK_EVT_MODE_ONESHOT: