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localtimer.c

/*
 *  linux/arch/arm/mach-realview/localtimer.c
 *
 *  Copyright (C) 2002 ARM Ltd.
 *  All Rights Reserved
 *
 * 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
 * published by the Free Software Foundation.
 */
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/smp.h>
#include <linux/jiffies.h>
#include <linux/percpu.h>
#include <linux/clockchips.h>
#include <linux/irq.h>

#include <asm/hardware/arm_twd.h>
#include <asm/hardware/gic.h>
#include <asm/hardware.h>
#include <asm/io.h>
#include <asm/irq.h>

static DEFINE_PER_CPU(struct clock_event_device, local_clockevent);

/*
 * Used on SMP for either the local timer or IPI_TIMER
 */
void local_timer_interrupt(void)
{
      struct clock_event_device *clk = &__get_cpu_var(local_clockevent);

      clk->event_handler(clk);
}

#ifdef CONFIG_LOCAL_TIMERS

#define TWD_BASE(cpu)   (twd_base_addr + (cpu) * twd_size)

/* set up by the platform code */
void __iomem *twd_base_addr;
unsigned int twd_size;

static unsigned long mpcore_timer_rate;

static void local_timer_set_mode(enum clock_event_mode mode,
                         struct clock_event_device *clk)
{
      void __iomem *base = TWD_BASE(smp_processor_id());
      unsigned long ctrl;

      switch(mode) {
      case CLOCK_EVT_MODE_PERIODIC:
            /* timer load already set up */
            ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
                  | TWD_TIMER_CONTROL_PERIODIC;
            break;
      case CLOCK_EVT_MODE_ONESHOT:
            /* period set, and timer enabled in 'next_event' hook */
            ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT;
            break;
      case CLOCK_EVT_MODE_UNUSED:
      case CLOCK_EVT_MODE_SHUTDOWN:
      default:
            ctrl = 0;
      }

      __raw_writel(ctrl, base + TWD_TIMER_CONTROL);
}

static int local_timer_set_next_event(unsigned long evt,
                              struct clock_event_device *unused)
{
      void __iomem *base = TWD_BASE(smp_processor_id());
      unsigned long ctrl = __raw_readl(base + TWD_TIMER_CONTROL);

      __raw_writel(evt, base + TWD_TIMER_COUNTER);
      __raw_writel(ctrl | TWD_TIMER_CONTROL_ENABLE, base + TWD_TIMER_CONTROL);

      return 0;
}

/*
 * local_timer_ack: checks for a local timer interrupt.
 *
 * If a local timer interrupt has occurred, acknowledge and return 1.
 * Otherwise, return 0.
 */
int local_timer_ack(void)
{
      void __iomem *base = TWD_BASE(smp_processor_id());

      if (__raw_readl(base + TWD_TIMER_INTSTAT)) {
            __raw_writel(1, base + TWD_TIMER_INTSTAT);
            return 1;
      }

      return 0;
}

static void __cpuinit twd_calibrate_rate(unsigned int cpu)
{
      void __iomem *base = TWD_BASE(cpu);
      unsigned long load, count;
      u64 waitjiffies;

      /*
       * If this is the first time round, we need to work out how fast
       * the timer ticks
       */
      if (mpcore_timer_rate == 0) {
            printk("Calibrating local timer... ");

            /* Wait for a tick to start */
            waitjiffies = get_jiffies_64() + 1;

            while (get_jiffies_64() < waitjiffies)
                  udelay(10);

            /* OK, now the tick has started, let's get the timer going */
            waitjiffies += 5;

                         /* enable, no interrupt or reload */
            __raw_writel(0x1, base + TWD_TIMER_CONTROL);

                         /* maximum value */
            __raw_writel(0xFFFFFFFFU, base + TWD_TIMER_COUNTER);

            while (get_jiffies_64() < waitjiffies)
                  udelay(10);

            count = __raw_readl(base + TWD_TIMER_COUNTER);

            mpcore_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);

            printk("%lu.%02luMHz.\n", mpcore_timer_rate / 1000000,
                  (mpcore_timer_rate / 100000) % 100);
      }

      load = mpcore_timer_rate / HZ;

      __raw_writel(load, base + TWD_TIMER_LOAD);
}

/*
 * Setup the local clock events for a CPU.
 */
void __cpuinit local_timer_setup(unsigned int cpu)
{
      struct clock_event_device *clk = &per_cpu(local_clockevent, cpu);
      unsigned long flags;

      twd_calibrate_rate(cpu);

      clk->name         = "local_timer";
      clk->features           = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
      clk->rating       = 350;
      clk->set_mode           = local_timer_set_mode;
      clk->set_next_event     = local_timer_set_next_event;
      clk->irq          = IRQ_LOCALTIMER;
      clk->cpumask            = cpumask_of_cpu(cpu);
      clk->shift        = 20;
      clk->mult         = div_sc(mpcore_timer_rate, NSEC_PER_SEC, clk->shift);
      clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
      clk->min_delta_ns = clockevent_delta2ns(0xf, clk);

      /* Make sure our local interrupt controller has this enabled */
      local_irq_save(flags);
      get_irq_chip(IRQ_LOCALTIMER)->unmask(IRQ_LOCALTIMER);
      local_irq_restore(flags);

      clockevents_register_device(clk);
}

/*
 * take a local timer down
 */
void __cpuexit local_timer_stop(unsigned int cpu)
{
      __raw_writel(0, TWD_BASE(cpu) + TWD_TIMER_CONTROL);
}

#else /* CONFIG_LOCAL_TIMERS */

static void dummy_timer_set_mode(enum clock_event_mode mode,
                         struct clock_event_device *clk)
{
}

void __cpuinit local_timer_setup(unsigned int cpu)
{
      struct clock_event_device *clk = &per_cpu(local_clockevent, cpu);

      clk->name         = "dummy_timer";
      clk->features           = CLOCK_EVT_FEAT_DUMMY;
      clk->rating       = 200;
      clk->set_mode           = dummy_timer_set_mode;
      clk->broadcast          = smp_timer_broadcast;
      clk->cpumask            = cpumask_of_cpu(cpu);

      clockevents_register_device(clk);
}

#endif      /* !CONFIG_LOCAL_TIMERS */

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