ARM: Add HRT clockevent support for IXP4xx platform

Signed-off-by: Milan Svoboda <msvoboda@ra.rockwell.com>
Signed-off-by: Kevin Hilman <khilman@deeprooted.net>

Index: ixp4xx/arch/arm/mach-ixp4xx/common.c
===================================================================
--- ixp4xx.orig/arch/arm/mach-ixp4xx/common.c
+++ ixp4xx/arch/arm/mach-ixp4xx/common.c
@@ -28,6 +28,7 @@
 #include <linux/time.h>
 #include <linux/timex.h>
 #include <linux/clocksource.h>
+#include <linux/clockchips.h>
 
 #include <asm/hardware.h>
 #include <asm/uaccess.h>
@@ -256,15 +257,31 @@ void __init ixp4xx_init_irq(void)
 
 static unsigned volatile last_jiffy_time;
 
-#define CLOCK_TICKS_PER_USEC	((CLOCK_TICK_RATE + USEC_PER_SEC/2) / USEC_PER_SEC)
+#ifdef CONFIG_HIGH_RES_TIMERS
+static void ixp4xx_set_next_event(unsigned long evt, void *priv)
+{
+	*IXP4XX_OSRT1 = (evt & ~IXP4XX_OST_RELOAD_MASK) | IXP4XX_OST_ENABLE;
+}
+
+static struct clock_event clockevent_ixp4xx = {
+	.name		= "OSTS clock event interface",
+	.capabilities	= CLOCK_CAP_NEXTEVT |  CLOCK_HAS_IRQHANDLER,
+	.shift		= 32,
+	.set_next_event	= ixp4xx_set_next_event,
+};
+#endif
 
 static irqreturn_t ixp4xx_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 {
-	write_seqlock(&xtime_lock);
-
 	/* Clear Pending Interrupt by writing '1' to it */
 	*IXP4XX_OSST = IXP4XX_OSST_TIMER_1_PEND;
 
+#ifdef CONFIG_HIGH_RES_TIMERS
+	if (clockevent_ixp4xx.event_handler)
+		clockevent_ixp4xx.event_handler(regs, NULL);
+#endif
+	write_seqlock(&xtime_lock);
+
 	/*
 	 * Catch up with the real idea of time
 	 */
@@ -404,7 +421,7 @@ static struct clocksource clocksource_ix
 	.rating		= 200,
 	.read		= ixp4xx_get_cycles,
 	.mask		= 0xFFFFFFFF,
-	.shift 		= 10,
+	.shift 		= 20,
 	.is_continuous 	= 1,
 };
 
@@ -419,5 +436,19 @@ static int __init ixp4xx_clocksource_ini
 
 	return 0;
 }
-
 device_initcall(ixp4xx_clocksource_init);
+
+#ifdef CONFIG_HIGH_RES_TIMERS
+static int __init ixp4xx_clockevent_init(void)
+{
+	clockevent_ixp4xx.mult = div_sc32(FREQ, NSEC_PER_SEC);
+	clockevent_ixp4xx.max_delta_ns =
+		clockevent_delta2ns(0xfffffffe, &clockevent_ixp4xx);
+	clockevent_ixp4xx.min_delta_ns =
+		clockevent_delta2ns(0xf, &clockevent_ixp4xx);
+	setup_local_clockevent(&clockevent_ixp4xx, CPU_MASK_NONE);
+
+	return 0;
+}
+device_initcall(ixp4xx_clockevent_init);
+#endif