[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>

2 files changed, 109 insertions, 14 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 8b553954365f..9dc455ef9eb5 100644
--- a/arch/arm/Kconfig
+++ b/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).
 
diff --git a/arch/arm/mach-imx/time.c b/arch/arm/mach-imx/time.c
index 6960a9d04217..010f6fa984a6 100644
--- a/arch/arm/mach-imx/time.c
+++ b/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
          */