[ARM] 4374/3: i.MX/MX1 clock event source

Support clock event source based on i.MX general purpose
timer in free running timer mode.
Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -242,6 +242,8 @@ config ARCH_H720X
 config ARCH_IMX
 	bool "IMX"
 	select GENERIC_GPIO
+	select GENERIC_TIME
+	select GENERIC_CLOCKEVENTS
 	help
 	  Support for Motorola's i.MX family of processors (MX1, MXL).
 

arch/arm/mach-imx/time.c

@@ -3,6 +3,7 @@
  *
  *  Copyright (C) 2000-2001 Deep Blue Solutions
  *  Copyright (C) 2002 Shane Nay (shane@minirl.com)
+ *  Copyright (C) 2006-2007 Pavel Pisa (ppisa@pikron.com)
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
@@ -15,6 +16,7 @@
 #include <linux/irq.h>
 #include <linux/time.h>
 #include <linux/clocksource.h>
+#include <linux/clockchips.h>
 
 #include <asm/hardware.h>
 #include <asm/io.h>
@@ -25,7 +27,8 @@
 /* Use timer 1 as system timer */
 #define TIMER_BASE IMX_TIM1_BASE
 
-static unsigned long evt_diff;
+static struct clock_event_device clockevent_imx;
+static enum clock_event_mode clockevent_mode = CLOCK_EVT_MODE_UNUSED;
 
 /*
  * IRQ handler for the timer
@@ -33,25 +36,20 @@ static unsigned long evt_diff;
 static irqreturn_t
 imx_timer_interrupt(int irq, void *dev_id)
 {
+	struct clock_event_device *evt = &clockevent_imx;
 	uint32_t tstat;
+	irqreturn_t ret = IRQ_NONE;
 
 	/* clear the interrupt */
 	tstat = IMX_TSTAT(TIMER_BASE);
 	IMX_TSTAT(TIMER_BASE) = 0;
 
 	if (tstat & TSTAT_COMP) {
-		do {
-
-			write_seqlock(&xtime_lock);
-			timer_tick();
-			write_sequnlock(&xtime_lock);
-			IMX_TCMP(TIMER_BASE) += evt_diff;
-
-		} while (unlikely((int32_t)(IMX_TCMP(TIMER_BASE)
-					- IMX_TCN(TIMER_BASE)) < 0));
+		evt->event_handler(evt);
+		ret = IRQ_HANDLED;
 	}
 
-	return IRQ_HANDLED;
+	return ret;
 }
 
 static struct irqaction imx_timer_irq = {
@@ -70,10 +68,8 @@ static void __init imx_timer_hardware_init(void)
 	 */
 	IMX_TCTL(TIMER_BASE) = 0;
 	IMX_TPRER(TIMER_BASE) = 0;
-	IMX_TCMP(TIMER_BASE) = LATCH - 1;
 
-	IMX_TCTL(TIMER_BASE) = TCTL_FRR | TCTL_CLK_PCLK1 | TCTL_IRQEN | TCTL_TEN;
-	evt_diff = LATCH;
+	IMX_TCTL(TIMER_BASE) = TCTL_FRR | TCTL_CLK_PCLK1 | TCTL_TEN;
 }
 
 cycle_t imx_get_cycles(void)
@@ -99,11 +95,108 @@ static int __init imx_clocksource_init(void)
 	return 0;
 }
 
+static int imx_set_next_event(unsigned long evt,
+				  struct clock_event_device *unused)
+{
+	unsigned long tcmp;
+
+	tcmp = IMX_TCN(TIMER_BASE) + evt;
+	IMX_TCMP(TIMER_BASE) = tcmp;
+
+	return (int32_t)(tcmp - IMX_TCN(TIMER_BASE)) < 0 ? -ETIME : 0;
+}
+
+#ifdef DEBUG
+static const char *clock_event_mode_label[]={
+	[CLOCK_EVT_MODE_PERIODIC] = "CLOCK_EVT_MODE_PERIODIC",
+	[CLOCK_EVT_MODE_ONESHOT]  = "CLOCK_EVT_MODE_ONESHOT",
+	[CLOCK_EVT_MODE_SHUTDOWN] = "CLOCK_EVT_MODE_SHUTDOWN",
+	[CLOCK_EVT_MODE_UNUSED]   = "CLOCK_EVT_MODE_UNUSED"
+};
+#endif /*DEBUG*/
+
+static void imx_set_mode(enum clock_event_mode mode, struct clock_event_device *evt)
+{
+	unsigned long flags;
+
+	/*
+	 * The timer interrupt generation is disabled at least
+	 * for enough time to call imx_set_next_event()
+	 */
+	local_irq_save(flags);
+	/* Disable interrupt in GPT module */
+	IMX_TCTL(TIMER_BASE) &= ~TCTL_IRQEN;
+	if (mode != clockevent_mode) {
+		/* Set event time into far-far future */
+		IMX_TCMP(TIMER_BASE) = IMX_TCN(TIMER_BASE) - 3;
+		/* Clear pending interrupt */
+		IMX_TSTAT(TIMER_BASE) &= ~TSTAT_COMP;
+	}
+
+#ifdef DEBUG
+	printk(KERN_INFO "imx_set_mode: changing mode from %s to %s\n",
+		clock_event_mode_label[clockevent_mode], clock_event_mode_label[mode]);
+#endif /*DEBUG*/
+
+	/* Remember timer mode */
+	clockevent_mode = mode;
+	local_irq_restore(flags);
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		printk(KERN_ERR "imx_set_mode: Periodic mode is not supported for i.MX\n");
+		break;
+	case CLOCK_EVT_MODE_ONESHOT:
+		/*
+		 * Do not put overhead of interrupt enable/disable into
+		 * imx_set_next_event(), the core has about 4 minutes
+		 * to call imx_set_next_event() or shutdown clock after
+		 * mode switching
+		 */
+		local_irq_save(flags);
+		IMX_TCTL(TIMER_BASE) |= TCTL_IRQEN;
+		local_irq_restore(flags);
+		break;
+	case CLOCK_EVT_MODE_SHUTDOWN:
+	case CLOCK_EVT_MODE_UNUSED:
+		/* Left event sources disabled, no more interrupts appears */
+		break;
+	}
+}
+
+static struct clock_event_device clockevent_imx = {
+	.name		= "imx_timer1",
+	.features	= CLOCK_EVT_FEAT_ONESHOT,
+	.shift		= 32,
+	.set_mode	= imx_set_mode,
+	.set_next_event	= imx_set_next_event,
+	.rating		= 200,
+};
+
+static int __init imx_clockevent_init(void)
+{
+	clockevent_imx.mult = div_sc(imx_get_perclk1(), NSEC_PER_SEC,
+					clockevent_imx.shift);
+	clockevent_imx.max_delta_ns =
+		clockevent_delta2ns(0xfffffffe, &clockevent_imx);
+	clockevent_imx.min_delta_ns =
+		clockevent_delta2ns(0xf, &clockevent_imx);
+
+	clockevent_imx.cpumask = cpumask_of_cpu(0);
+
+	clockevents_register_device(&clockevent_imx);
+
+	return 0;
+}
+
+
 static void __init imx_timer_init(void)
 {
 	imx_timer_hardware_init();
 	imx_clocksource_init();
 
+	imx_clockevent_init();
+
 	/*
 	 * Make irqs happen for the system timer
 	 */