[PATCH] ARM: ep93xx: clockevent support

[burman.yan@gmail.com (Yan Burman)]

ARM: ep93xx: clockevent support
I have ported to 3.6-rc1 and slightly modified a previous patch for clockevent support for the ep93xx.
The porting mainly consists of sched_clock support.
Tested on 9302 based board.
From: Ahmed Ammar <aammar <at> edge-techno.com>
Signed-off-by: Yan Burman <burman.yan@gmail.com>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index e91c7cd..6dbb828 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -451,7 +451,7 @@ config ARCH_EP93XX
 	select CLKDEV_LOOKUP
 	select ARCH_REQUIRE_GPIOLIB
 	select ARCH_HAS_HOLES_MEMORYMODEL
-	select ARCH_USES_GETTIMEOFFSET
+	select GENERIC_CLOCKEVENTS
 	select NEED_MACH_MEMORY_H
 	help
 	  This enables support for the Cirrus EP93xx series of CPUs.
diff --git a/arch/arm/mach-ep93xx/core.c b/arch/arm/mach-ep93xx/core.c
index 4afe52a..1497cba 100644
--- a/arch/arm/mach-ep93xx/core.c
+++ b/arch/arm/mach-ep93xx/core.c
@@ -30,6 +30,8 @@
 #include <linux/amba/bus.h>
 #include <linux/amba/serial.h>
 #include <linux/mtd/physmap.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
 #include <linux/i2c.h>
 #include <linux/i2c-gpio.h>
 #include <linux/spi/spi.h>
@@ -43,6 +45,7 @@
 
 #include <asm/mach/map.h>
 #include <asm/mach/time.h>
+#include <asm/sched_clock.h>
 
 #include <asm/hardware/vic.h>
 
@@ -114,63 +117,129 @@ void __init ep93xx_map_io(void)
 #define EP93XX_TIMER4_CLOCK		983040
 
 #define TIMER1_RELOAD			((EP93XX_TIMER123_CLOCK / HZ) - 1)
-#define TIMER4_TICKS_PER_JIFFY		DIV_ROUND_CLOSEST(CLOCK_TICK_RATE, HZ)
-
-static unsigned int last_jiffy_time;
 
 static irqreturn_t ep93xx_timer_interrupt(int irq, void *dev_id)
 {
-	/* Writing any value clears the timer interrupt */
-	__raw_writel(1, EP93XX_TIMER1_CLEAR);
+	struct clock_event_device *evt = dev_id;
 
-	/* Recover lost jiffies */
-	while ((signed long)
-		(__raw_readl(EP93XX_TIMER4_VALUE_LOW) - last_jiffy_time)
-						>= TIMER4_TICKS_PER_JIFFY) {
-		last_jiffy_time += TIMER4_TICKS_PER_JIFFY;
-		timer_tick();
-	}
+	__raw_writel(1, EP93XX_TIMER1_CLEAR);
+	evt->event_handler(evt);
 
 	return IRQ_HANDLED;
 }
 
+static int ep93xx_set_next_event(unsigned long evt,
+				struct clock_event_device *unused)
+{
+	u32 tmode = __raw_readl(EP93XX_TIMER1_CONTROL);
+
+	/* stop timer */
+	__raw_writel(tmode & ~EP93XX_TIMER123_CONTROL_ENABLE,
+			EP93XX_TIMER1_CONTROL);
+	/* program timer */
+	__raw_writel(evt, EP93XX_TIMER1_LOAD);
+	/* start timer */
+	__raw_writel(tmode | EP93XX_TIMER123_CONTROL_ENABLE,
+			EP93XX_TIMER1_CONTROL);
+
+	return 0;
+}
+
+static void ep93xx_set_mode(enum clock_event_mode mode,
+			    struct clock_event_device *evt)
+{
+	u32 tmode = EP93XX_TIMER123_CONTROL_CLKSEL;
+	/* Disable timer */
+	__raw_writel(tmode, EP93XX_TIMER1_CONTROL);
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		/* Set timer period  */
+		__raw_writel((508469 / HZ) - 1, EP93XX_TIMER1_LOAD);
+		tmode |= EP93XX_TIMER123_CONTROL_MODE;
+
+	case CLOCK_EVT_MODE_ONESHOT:
+		tmode |= EP93XX_TIMER123_CONTROL_ENABLE;
+		__raw_writel(tmode, EP93XX_TIMER1_CONTROL);
+		break;
+
+	case CLOCK_EVT_MODE_SHUTDOWN:
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_RESUME:
+		return;
+	}
+}
+
+static struct clock_event_device clockevent_ep93xx = {
+	.name		= "ep93xx-timer1",
+	.features	= CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
+	.shift		= 32,
+	.set_mode	= ep93xx_set_mode,
+	.set_next_event	= ep93xx_set_next_event,
+};
+
 static struct irqaction ep93xx_timer_irq = {
 	.name		= "ep93xx timer",
 	.flags		= IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
 	.handler	= ep93xx_timer_interrupt,
+	.dev_id		= &clockevent_ep93xx,
 };
 
-static void __init ep93xx_timer_init(void)
+static void __init ep93xx_clockevent_init(void)
 {
-	u32 tmode = EP93XX_TIMER123_CONTROL_MODE |
-		    EP93XX_TIMER123_CONTROL_CLKSEL;
+	setup_irq(IRQ_EP93XX_TIMER1, &ep93xx_timer_irq);
+	clockevent_ep93xx.mult = div_sc(508469, NSEC_PER_SEC,
+					clockevent_ep93xx.shift);
+	clockevent_ep93xx.max_delta_ns =
+		clockevent_delta2ns(0xfffffffe, &clockevent_ep93xx);
+	clockevent_ep93xx.min_delta_ns =
+		clockevent_delta2ns(0xf, &clockevent_ep93xx);
+	clockevent_ep93xx.cpumask = cpumask_of(0);
+	clockevents_register_device(&clockevent_ep93xx);
+}
 
-	/* Enable periodic HZ timer.  */
-	__raw_writel(tmode, EP93XX_TIMER1_CONTROL);
-	__raw_writel(TIMER1_RELOAD, EP93XX_TIMER1_LOAD);
-	__raw_writel(tmode | EP93XX_TIMER123_CONTROL_ENABLE,
-			EP93XX_TIMER1_CONTROL);
+/*
+ * timer4 is a 40 Bit timer, separated in a 32bit and a 8 bit
+ * register, EP93XX_TIMER4_VALUE_LOW stores 32 bit word. The
+ * controlregister is in EP93XX_TIMER4_VALUE_HIGH
+ */
+static cycle_t ep93xx_get_cycles(struct clocksource *unused)
+{
+	return __raw_readl(EP93XX_TIMER4_VALUE_LOW);
+}
 
-	/* Enable lost jiffy timer.  */
-	__raw_writel(EP93XX_TIMER4_VALUE_HIGH_ENABLE,
-			EP93XX_TIMER4_VALUE_HIGH);
+static struct clocksource clocksource_ep93xx = {
+	.name		= "ep93xx_timer4",
+	.rating		= 200,
+	.read		= ep93xx_get_cycles,
+	.mask		= 0xFFFFFFFF,
+	.shift		= 20,
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
 
-	setup_irq(IRQ_EP93XX_TIMER1, &ep93xx_timer_irq);
+static void __init ep93xx_clocksource_init(void)
+{
+	/* Reset time-stamp counter */
+	__raw_writel(0x100, EP93XX_TIMER4_VALUE_HIGH);
+	clocksource_ep93xx.mult =
+		clocksource_hz2mult(983040, clocksource_ep93xx.shift);
+	clocksource_register(&clocksource_ep93xx);
 }
 
-static unsigned long ep93xx_gettimeoffset(void)
+static u32 notrace ep93xx_sched_clock(void)
 {
-	int offset;
-
-	offset = __raw_readl(EP93XX_TIMER4_VALUE_LOW) - last_jiffy_time;
+	return __raw_readl(EP93XX_TIMER4_VALUE_LOW);
+}
 
-	/* Calculate (1000000 / 983040) * offset.  */
-	return offset + (53 * offset / 3072);
+static void __init ep93xx_timer_init(void)
+{
+	ep93xx_clocksource_init();
+	ep93xx_clockevent_init();
+	setup_sched_clock(ep93xx_sched_clock, 32, CLOCK_TICK_RATE);
 }
 
 struct sys_timer ep93xx_timer = {
 	.init		= ep93xx_timer_init,
-	.offset		= ep93xx_gettimeoffset,
 };