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time.c

/*
 *  linux/arch/arm/plat-mxc/time.c
 *
 *  Copyright (C) 2000-2001 Deep Blue Solutions
 *  Copyright (C) 2002 Shane Nay (shane@minirl.com)
 *  Copyright (C) 2006-2007 Pavel Pisa (ppisa@pikron.com)
 *  Copyright (C) 2008 Juergen Beisert (kernel@pengutronix.de)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301, USA.
 */

#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/clockchips.h>
#include <linux/clk.h>

#include <mach/hardware.h>
#include <asm/mach/time.h>
#include <mach/common.h>
#include <mach/mxc_timer.h>

static struct clock_event_device clockevent_mxc;
static enum clock_event_mode clockevent_mode = CLOCK_EVT_MODE_UNUSED;

/* clock source for the timer */
static struct clk *timer_clk;

/* clock source */

static cycle_t mxc_get_cycles(void)
{
      return __raw_readl(TIMER_BASE + MXC_TCN);
}

static struct clocksource clocksource_mxc = {
      .name             = "mxc_timer1",
      .rating           = 200,
      .read       = mxc_get_cycles,
      .mask       = CLOCKSOURCE_MASK(32),
      .shift            = 20,
      .flags            = CLOCK_SOURCE_IS_CONTINUOUS,
};

static int __init mxc_clocksource_init(void)
{
      unsigned int clock;

      clock = clk_get_rate(timer_clk);

      clocksource_mxc.mult = clocksource_hz2mult(clock,
                              clocksource_mxc.shift);
      clocksource_register(&clocksource_mxc);

      return 0;
}

/* clock event */

static int mxc_set_next_event(unsigned long evt,
                        struct clock_event_device *unused)
{
      unsigned long tcmp;

      tcmp = __raw_readl(TIMER_BASE + MXC_TCN) + evt;
      __raw_writel(tcmp, TIMER_BASE + MXC_TCMP);

      return (int)(tcmp - __raw_readl(TIMER_BASE + MXC_TCN)) < 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 mxc_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 mxc_set_next_event()
       */
      local_irq_save(flags);

      /* Disable interrupt in GPT module */
      gpt_irq_disable();

      if (mode != clockevent_mode) {
            /* Set event time into far-far future */
            __raw_writel(__raw_readl(TIMER_BASE + MXC_TCN) - 3,
                        TIMER_BASE + MXC_TCMP);
            /* Clear pending interrupt */
            gpt_irq_acknowledge();
      }

#ifdef DEBUG
      printk(KERN_INFO "mxc_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"mxc_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
       * mxc_set_next_event(), the core has about 4 minutes
       * to call mxc_set_next_event() or shutdown clock after
       * mode switching
       */
            local_irq_save(flags);
            gpt_irq_enable();
            local_irq_restore(flags);
            break;
      case CLOCK_EVT_MODE_SHUTDOWN:
      case CLOCK_EVT_MODE_UNUSED:
      case CLOCK_EVT_MODE_RESUME:
            /* Left event sources disabled, no more interrupts appear */
            break;
      }
}

/*
 * IRQ handler for the timer
 */
static irqreturn_t mxc_timer_interrupt(int irq, void *dev_id)
{
      struct clock_event_device *evt = &clockevent_mxc;
      uint32_t tstat;

      tstat = __raw_readl(TIMER_BASE + MXC_TSTAT);

      gpt_irq_acknowledge();

      evt->event_handler(evt);

      return IRQ_HANDLED;
}

static struct irqaction mxc_timer_irq = {
      .name       = "i.MX Timer Tick",
      .flags            = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
      .handler    = mxc_timer_interrupt,
};

static struct clock_event_device clockevent_mxc = {
      .name       = "mxc_timer1",
      .features   = CLOCK_EVT_FEAT_ONESHOT,
      .shift            = 32,
      .set_mode   = mxc_set_mode,
      .set_next_event   = mxc_set_next_event,
      .rating           = 200,
};

static int __init mxc_clockevent_init(void)
{
      unsigned int clock;

      clock = clk_get_rate(timer_clk);

      clockevent_mxc.mult = div_sc(clock, NSEC_PER_SEC,
                              clockevent_mxc.shift);
      clockevent_mxc.max_delta_ns =
                  clockevent_delta2ns(0xfffffffe, &clockevent_mxc);
      clockevent_mxc.min_delta_ns =
                  clockevent_delta2ns(0xff, &clockevent_mxc);

      clockevent_mxc.cpumask = cpumask_of_cpu(0);

      clockevents_register_device(&clockevent_mxc);

      return 0;
}

void __init mxc_timer_init(const char *clk_timer)
{
      timer_clk = clk_get(NULL, clk_timer);
      if (!timer_clk) {
            printk(KERN_ERR"Cannot determine timer clock. Giving up.\n");
            return;
      }

      clk_enable(timer_clk);

      /*
       * Initialise to a known state (all timers off, and timing reset)
       */
      __raw_writel(0, TIMER_BASE + MXC_TCTL);
      __raw_writel(0, TIMER_BASE + MXC_TPRER); /* see datasheet note */

      __raw_writel(TCTL_FRR | /* free running */
                 TCTL_VAL |   /* set clocksource and arch specific bits */
                 TCTL_TEN,    /* start the timer */
                 TIMER_BASE + MXC_TCTL);

      /* init and register the timer to the framework */
      mxc_clocksource_init();
      mxc_clockevent_init();

      /* Make irqs happen */
      setup_irq(TIMER_INTERRUPT, &mxc_timer_irq);
}


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