[ARM] sa1100: add clock event support

d142b6e77d394a4fcc0a42381b03852bd9c4e263 added clock source support,
now it's time for the clock event support.

Tested-by: Thomas Kunze <thommycheck@gmx.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -425,6 +425,8 @@ config ARCH_SA1100
 	select ARCH_MTD_XIP
 	select GENERIC_GPIO
 	select GENERIC_TIME
+	select GENERIC_CLOCKEVENTS
+	select TICK_ONESHOT
 	select HAVE_IDE
 	select HAVE_GPIO_LIB
 	help

arch/arm/mach-sa1100/time.c

@@ -13,67 +13,69 @@
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/timex.h>
-#include <linux/signal.h>
-#include <linux/clocksource.h>
+#include <linux/clockchips.h>
 
 #include <asm/mach/time.h>
 #include <asm/hardware.h>
 
-#define RTC_DEF_DIVIDER		(32768 - 1)
-#define RTC_DEF_TRIM            0
+#define MIN_OSCR_DELTA 2
 
-static int sa1100_set_rtc(void)
+static irqreturn_t sa1100_ost0_interrupt(int irq, void *dev_id)
 {
-	unsigned long current_time = xtime.tv_sec;
+	struct clock_event_device *c = dev_id;
 
-	if (RTSR & RTSR_ALE) {
-		/* make sure not to forward the clock over an alarm */
-		unsigned long alarm = RTAR;
-		if (current_time >= alarm && alarm >= RCNR)
-			return -ERESTARTSYS;
-	}
-	RCNR = current_time;
-	return 0;
-}
+	/* Disarm the compare/match, signal the event. */
+	OIER &= ~OIER_E0;
+	OSSR = OSSR_M0;
+	c->event_handler(c);
 
-#ifdef CONFIG_NO_IDLE_HZ
-static unsigned long initial_match;
-static int match_posponed;
-#endif
+	return IRQ_HANDLED;
+}
 
-static irqreturn_t
-sa1100_timer_interrupt(int irq, void *dev_id)
+static int
+sa1100_osmr0_set_next_event(unsigned long delta, struct clock_event_device *c)
 {
-	unsigned int next_match;
+	unsigned long flags, next, oscr;
 
-#ifdef CONFIG_NO_IDLE_HZ
-	if (match_posponed) {
-		match_posponed = 0;
-		OSMR0 = initial_match;
-	}
-#endif
+	raw_local_irq_save(flags);
+	OIER |= OIER_E0;
+	next = OSCR + delta;
+	OSMR0 = next;
+	oscr = OSCR;
+	raw_local_irq_restore(flags);
 
-	/*
-	 * Loop until we get ahead of the free running timer.
-	 * This ensures an exact clock tick count and time accuracy.
-	 * Since IRQs are disabled at this point, coherence between
-	 * lost_ticks(updated in do_timer()) and the match reg value is
-	 * ensured, hence we can use do_gettimeofday() from interrupt
-	 * handlers.
-	 */
-	do {
-		timer_tick();
-		OSSR = OSSR_M0;  /* Clear match on timer 0 */
-		next_match = (OSMR0 += LATCH);
-	} while ((signed long)(next_match - OSCR) <= 0);
+	return (signed)(next - oscr) <= MIN_OSCR_DELTA ? -ETIME : 0;
+}
 
-	return IRQ_HANDLED;
+static void
+sa1100_osmr0_set_mode(enum clock_event_mode mode, struct clock_event_device *c)
+{
+	unsigned long flags;
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_ONESHOT:
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_SHUTDOWN:
+		raw_local_irq_save(flags);
+		OIER &= ~OIER_E0;
+		OSSR = OSSR_M0;
+		raw_local_irq_restore(flags);
+		break;
+
+	case CLOCK_EVT_MODE_RESUME:
+	case CLOCK_EVT_MODE_PERIODIC:
+		break;
+	}
 }
 
-static struct irqaction sa1100_timer_irq = {
-	.name		= "SA11xx Timer Tick",
-	.flags		= IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
-	.handler	= sa1100_timer_interrupt,
+static struct clock_event_device ckevt_sa1100_osmr0 = {
+	.name		= "osmr0",
+	.features	= CLOCK_EVT_FEAT_ONESHOT,
+	.shift		= 32,
+	.rating		= 200,
+	.cpumask	= CPU_MASK_CPU0,
+	.set_next_event	= sa1100_osmr0_set_next_event,
+	.set_mode	= sa1100_osmr0_set_mode,
 };
 
 static cycle_t sa1100_read_oscr(void)
@@ -90,62 +92,34 @@ static struct clocksource cksrc_sa1100_oscr = {
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
+static struct irqaction sa1100_timer_irq = {
+	.name		= "ost0",
+	.flags		= IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
+	.handler	= sa1100_ost0_interrupt,
+	.dev_id		= &ckevt_sa1100_osmr0,
+};
+
 static void __init sa1100_timer_init(void)
 {
-	unsigned long flags;
-
-	set_rtc = sa1100_set_rtc;
-
 	OIER = 0;		/* disable any timer interrupts */
 	OSSR = 0xf;		/* clear status on all timers */
-	setup_irq(IRQ_OST0, &sa1100_timer_irq);
-	local_irq_save(flags);
-	OIER = OIER_E0;		/* enable match on timer 0 to cause interrupts */
-	OSMR0 = OSCR + LATCH;	/* set initial match */
-	local_irq_restore(flags);
+
+	ckevt_sa1100_osmr0.mult =
+		div_sc(3686400, NSEC_PER_SEC, ckevt_sa1100_osmr0.shift);
+	ckevt_sa1100_osmr0.max_delta_ns =
+		clockevent_delta2ns(0x7fffffff, &ckevt_sa1100_osmr0);
+	ckevt_sa1100_osmr0.min_delta_ns =
+		clockevent_delta2ns(MIN_OSCR_DELTA * 2, &ckevt_sa1100_osmr0) + 1;
 
 	cksrc_sa1100_oscr.mult =
 		clocksource_hz2mult(CLOCK_TICK_RATE, cksrc_sa1100_oscr.shift);
 
-	clocksource_register(&cksrc_sa1100_oscr);
-}
-
-#ifdef CONFIG_NO_IDLE_HZ
-static int sa1100_dyn_tick_enable_disable(void)
-{
-	/* nothing to do */
-	return 0;
-}
-
-static void sa1100_dyn_tick_reprogram(unsigned long ticks)
-{
-	if (ticks > 1) {
-		initial_match = OSMR0;
-		OSMR0 = initial_match + ticks * LATCH;
-		match_posponed = 1;
-	}
-}
+	setup_irq(IRQ_OST0, &sa1100_timer_irq);
 
-static irqreturn_t
-sa1100_dyn_tick_handler(int irq, void *dev_id)
-{
-	if (match_posponed) {
-		match_posponed = 0;
-		OSMR0 = initial_match;
-		if ((signed long)(initial_match - OSCR) <= 0)
-			return sa1100_timer_interrupt(irq, dev_id);
-	}
-	return IRQ_NONE;
+	clocksource_register(&cksrc_sa1100_oscr);
+	clockevents_register_device(&ckevt_sa1100_osmr0);
 }
 
-static struct dyn_tick_timer sa1100_dyn_tick = {
-	.enable		= sa1100_dyn_tick_enable_disable,
-	.disable	= sa1100_dyn_tick_enable_disable,
-	.reprogram	= sa1100_dyn_tick_reprogram,
-	.handler	= sa1100_dyn_tick_handler,
-};
-#endif
-
 #ifdef CONFIG_PM
 unsigned long osmr[4], oier;
 
@@ -181,7 +155,4 @@ struct sys_timer sa1100_timer = {
 	.init		= sa1100_timer_init,
 	.suspend	= sa1100_timer_suspend,
 	.resume		= sa1100_timer_resume,
-#ifdef CONFIG_NO_IDLE_HZ
-	.dyn_tick	= &sa1100_dyn_tick,
-#endif
 };