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smp_twd.c

/*
 *  linux/arch/arm/kernel/smp_twd.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/clockchips.h>
#include <linux/irq.h>
#include <linux/io.h>

#include <asm/smp_twd.h>
#include <asm/hardware/gic.h>

#define TWD_TIMER_LOAD              0x00
#define TWD_TIMER_COUNTER           0x04
#define TWD_TIMER_CONTROL           0x08
#define TWD_TIMER_INTSTAT           0x0C

#define TWD_WDOG_LOAD               0x20
#define TWD_WDOG_COUNTER            0x24
#define TWD_WDOG_CONTROL            0x28
#define TWD_WDOG_INTSTAT            0x2C
#define TWD_WDOG_RESETSTAT          0x30
#define TWD_WDOG_DISABLE            0x34

#define TWD_TIMER_CONTROL_ENABLE    (1 << 0)
#define TWD_TIMER_CONTROL_ONESHOT   (0 << 1)
#define TWD_TIMER_CONTROL_PERIODIC  (1 << 1)
#define TWD_TIMER_CONTROL_IT_ENABLE (1 << 2)

/* set up by the platform code */
void __iomem *twd_base;

static unsigned long twd_timer_rate;

static void twd_set_mode(enum clock_event_mode mode,
                  struct clock_event_device *clk)
{
      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, twd_base + TWD_TIMER_CONTROL);
}

static int twd_set_next_event(unsigned long evt,
                  struct clock_event_device *unused)
{
      unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL);

      ctrl |= TWD_TIMER_CONTROL_ENABLE;

      __raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
      __raw_writel(ctrl, twd_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 twd_timer_ack(void)
{
      if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
            __raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
            return 1;
      }

      return 0;
}

static void __cpuinit twd_calibrate_rate(void)
{
      unsigned long load, count;
      u64 waitjiffies;

      /*
       * If this is the first time round, we need to work out how fast
       * the timer ticks
       */
      if (twd_timer_rate == 0) {
            printk(KERN_INFO "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, twd_base + TWD_TIMER_CONTROL);

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

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

            count = __raw_readl(twd_base + TWD_TIMER_COUNTER);

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

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

      load = twd_timer_rate / HZ;

      __raw_writel(load, twd_base + TWD_TIMER_LOAD);
}

/*
 * Setup the local clock events for a CPU.
 */
void __cpuinit twd_timer_setup(struct clock_event_device *clk)
{
      unsigned long flags;

      twd_calibrate_rate();

      clk->name = "local_timer";
      clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
      clk->rating = 350;
      clk->set_mode = twd_set_mode;
      clk->set_next_event = twd_set_next_event;
      clk->shift = 20;
      clk->mult = div_sc(twd_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(clk->irq)->unmask(clk->irq);
      local_irq_restore(flags);

      clockevents_register_device(clk);
}

/*
 * take a local timer down
 */
void __cpuexit twd_timer_stop(void)
{
      __raw_writel(0, twd_base + TWD_TIMER_CONTROL);
}

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