ARM: 7085/2: mach-integrator: clockevent supports oneshot mode

The Integrator AP timer has no problem supporting oneshot
ticks with proper code, so let's do it so we can have
NOHZ configured in for this platform too.

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-integrator/integrator_ap.c

@@ -360,15 +360,29 @@ static void clkevt_set_mode(enum clock_event_mode mode, struct clock_event_devic
 {
 	u32 ctrl = readl(clkevt_base + TIMER_CTRL) & ~TIMER_CTRL_ENABLE;
 
-	BUG_ON(mode == CLOCK_EVT_MODE_ONESHOT);
+	/* Disable timer */
+	writel(ctrl, clkevt_base + TIMER_CTRL);
 
-	if (mode == CLOCK_EVT_MODE_PERIODIC) {
-		writel(ctrl, clkevt_base + TIMER_CTRL);
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		/* Enable the timer and start the periodic tick */
 		writel(timer_reload, clkevt_base + TIMER_LOAD);
 		ctrl |= TIMER_CTRL_PERIODIC | TIMER_CTRL_ENABLE;
+		writel(ctrl, clkevt_base + TIMER_CTRL);
+		break;
+	case CLOCK_EVT_MODE_ONESHOT:
+		/* Leave the timer disabled, .set_next_event will enable it */
+		ctrl &= ~TIMER_CTRL_PERIODIC;
+		writel(ctrl, clkevt_base + TIMER_CTRL);
+		break;
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_SHUTDOWN:
+	case CLOCK_EVT_MODE_RESUME:
+	default:
+		/* Just leave in disabled state */
+		break;
 	}
 
-	writel(ctrl, clkevt_base + TIMER_CTRL);
 }
 
 static int clkevt_set_next_event(unsigned long next, struct clock_event_device *evt)
@@ -385,7 +399,7 @@ static int clkevt_set_next_event(unsigned long next, struct clock_event_device *
 static struct clock_event_device integrator_clockevent = {
 	.name		= "timer1",
 	.shift		= 34,
-	.features	= CLOCK_EVT_FEAT_PERIODIC,
+	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
 	.set_mode	= clkevt_set_mode,
 	.set_next_event	= clkevt_set_next_event,
 	.rating		= 300,