LXR linux/arch/arm/kernel/smp

   1/*
   2 *  linux/arch/arm/kernel/smp_twd.c
   3 *
   4 *  Copyright (C) 2002 ARM Ltd.
   5 *  All Rights Reserved
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 */
  11#include <linux/init.h>
  12#include <linux/kernel.h>
  13#include <linux/delay.h>
  14#include <linux/device.h>
  15#include <linux/smp.h>
  16#include <linux/jiffies.h>
  17#include <linux/clockchips.h>
  18#include <linux/irq.h>
  19#include <linux/io.h>
  20
  21#include <asm/smp_twd.h>
  22#include <asm/hardware/gic.h>
  23
  24/* set up by the platform code */
  25void __iomem *twd_base;
  26
  27static unsigned long twd_timer_rate;
  28
  29static void twd_set_mode(enum clock_event_mode mode,
  30                        struct clock_event_device *clk)
  31{
  32        unsigned long ctrl;
  33
  34        switch (mode) {
  35        case CLOCK_EVT_MODE_PERIODIC:
  36                /* timer load already set up */
  37                ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
  38                        | TWD_TIMER_CONTROL_PERIODIC;
  39                __raw_writel(twd_timer_rate / HZ, twd_base + TWD_TIMER_LOAD);
  40                break;
  41        case CLOCK_EVT_MODE_ONESHOT:
  42                /* period set, and timer enabled in 'next_event' hook */
  43                ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT;
  44                break;
  45        case CLOCK_EVT_MODE_UNUSED:
  46        case CLOCK_EVT_MODE_SHUTDOWN:
  47        default:
  48                ctrl = 0;
  49        }
  50
  51        __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
  52}
  53
  54static int twd_set_next_event(unsigned long evt,
  55                        struct clock_event_device *unused)
  56{
  57        unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL);
  58
  59        ctrl |= TWD_TIMER_CONTROL_ENABLE;
  60
  61        __raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
  62        __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
  63
  64        return 0;
  65}
  66
  67/*
  68 * local_timer_ack: checks for a local timer interrupt.
  69 *
  70 * If a local timer interrupt has occurred, acknowledge and return 1.
  71 * Otherwise, return 0.
  72 */
  73int twd_timer_ack(void)
  74{
  75        if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
  76                __raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
  77                return 1;
  78        }
  79
  80        return 0;
  81}
  82
  83static void __cpuinit twd_calibrate_rate(void)
  84{
  85        unsigned long count;
  86        u64 waitjiffies;
  87
  88        /*
  89         * If this is the first time round, we need to work out how fast
  90         * the timer ticks
  91         */
  92        if (twd_timer_rate == 0) {
  93                printk(KERN_INFO "Calibrating local timer... ");
  94
  95                /* Wait for a tick to start */
  96                waitjiffies = get_jiffies_64() + 1;
  97
  98                while (get_jiffies_64() < waitjiffies)
  99                        udelay(10);
 100
 101                /* OK, now the tick has started, let's get the timer going */
 102                waitjiffies += 5;
 103
 104                                 /* enable, no interrupt or reload */
 105                __raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
 106
 107                                 /* maximum value */
 108                __raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
 109
 110                while (get_jiffies_64() < waitjiffies)
 111                        udelay(10);
 112
 113                count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
 114
 115                twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 116
 117                printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 118                        (twd_timer_rate / 1000000) % 100);
 119        }
 120}
 121
 122/*
 123 * Setup the local clock events for a CPU.
 124 */
 125void __cpuinit twd_timer_setup(struct clock_event_device *clk)
 126{
 127        twd_calibrate_rate();
 128
 129        clk->name = "local_timer";
 130        clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
 131                        CLOCK_EVT_FEAT_C3STOP;
 132        clk->rating = 350;
 133        clk->set_mode = twd_set_mode;
 134        clk->set_next_event = twd_set_next_event;
 135        clk->shift = 20;
 136        clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
 137        clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
 138        clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
 139
 140        /* Make sure our local interrupt controller has this enabled */
 141        gic_enable_ppi(clk->irq);
 142
 143        clockevents_register_device(clk);
 144}
 145