[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>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 8b55395..9dc455e 100644 (file)
--- 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 6960a9d..010f6fa 100644 (file)
--- 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
         */