arch/arm/kernel/smp_twd.c

   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 #define TWD_TIMER_LOAD                  0x00
  25 #define TWD_TIMER_COUNTER               0x04
  26 #define TWD_TIMER_CONTROL               0x08
  27 #define TWD_TIMER_INTSTAT               0x0C
  28
  29 #define TWD_WDOG_LOAD                   0x20
  30 #define TWD_WDOG_COUNTER                0x24
  31 #define TWD_WDOG_CONTROL                0x28
  32 #define TWD_WDOG_INTSTAT                0x2C
  33 #define TWD_WDOG_RESETSTAT              0x30
  34 #define TWD_WDOG_DISABLE                0x34
  35
  36 #define TWD_TIMER_CONTROL_ENABLE        (1 << 0)
  37 #define TWD_TIMER_CONTROL_ONESHOT       (0 << 1)
  38 #define TWD_TIMER_CONTROL_PERIODIC      (1 << 1)
  39 #define TWD_TIMER_CONTROL_IT_ENABLE     (1 << 2)
  40
  41 /* set up by the platform code */
  42 void __iomem *twd_base;
  43
  44 static unsigned long twd_timer_rate;
  45
  46 static void twd_set_mode(enum clock_event_mode mode,
  47                         struct clock_event_device *clk)
  48 {
  49         unsigned long ctrl;
  50
  51         switch(mode) {
  52         case CLOCK_EVT_MODE_PERIODIC:
  53                 /* timer load already set up */
  54                 ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
  55                         | TWD_TIMER_CONTROL_PERIODIC;
  56                 break;
  57         case CLOCK_EVT_MODE_ONESHOT:
  58                 /* period set, and timer enabled in 'next_event' hook */
  59                 ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT;
  60                 break;
  61         case CLOCK_EVT_MODE_UNUSED:
  62         case CLOCK_EVT_MODE_SHUTDOWN:
  63         default:
  64                 ctrl = 0;
  65         }
  66
  67         __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
  68 }
  69
  70 static int twd_set_next_event(unsigned long evt,
  71                         struct clock_event_device *unused)
  72 {
  73         unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL);
  74
  75         __raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
  76         __raw_writel(ctrl | TWD_TIMER_CONTROL_ENABLE, twd_base + TWD_TIMER_CONTROL);
  77
  78         return 0;
  79 }
  80
  81 /*
  82  * local_timer_ack: checks for a local timer interrupt.
  83  *
  84  * If a local timer interrupt has occurred, acknowledge and return 1.
  85  * Otherwise, return 0.
  86  */
  87 int twd_timer_ack(void)
  88 {
  89         if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
  90                 __raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
  91                 return 1;
  92         }
  93
  94         return 0;
  95 }
  96
  97 static void __cpuinit twd_calibrate_rate(void)
  98 {
  99         unsigned long load, count;
 100         u64 waitjiffies;
 101
 102         /*
 103          * If this is the first time round, we need to work out how fast
 104          * the timer ticks
 105          */
 106         if (twd_timer_rate == 0) {
 107                 printk("Calibrating local timer... ");
 108
 109                 /* Wait for a tick to start */
 110                 waitjiffies = get_jiffies_64() + 1;
 111
 112                 while (get_jiffies_64() < waitjiffies)
 113                         udelay(10);
 114
 115                 /* OK, now the tick has started, let's get the timer going */
 116                 waitjiffies += 5;
 117
 118                                  /* enable, no interrupt or reload */
 119                 __raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
 120
 121                                  /* maximum value */
 122                 __raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
 123
 124                 while (get_jiffies_64() < waitjiffies)
 125                         udelay(10);
 126
 127                 count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
 128
 129                 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 130
 131                 printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 132                         (twd_timer_rate / 100000) % 100);
 133         }
 134
 135         load = twd_timer_rate / HZ;
 136
 137         __raw_writel(load, twd_base + TWD_TIMER_LOAD);
 138 }
 139
 140 /*
 141  * Setup the local clock events for a CPU.
 142  */
 143 void __cpuinit twd_timer_setup(struct clock_event_device *clk)
 144 {
 145         unsigned long flags;
 146
 147         twd_calibrate_rate();
 148
 149         clk->name               = "local_timer";
 150         clk->features           = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
 151         clk->rating             = 350;
 152         clk->set_mode           = twd_set_mode;
 153         clk->set_next_event     = twd_set_next_event;
 154         clk->shift              = 20;
 155         clk->mult               = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
 156         clk->max_delta_ns       = clockevent_delta2ns(0xffffffff, clk);
 157         clk->min_delta_ns       = clockevent_delta2ns(0xf, clk);
 158
 159         /* Make sure our local interrupt controller has this enabled */
 160         local_irq_save(flags);
 161         get_irq_chip(clk->irq)->unmask(clk->irq);
 162         local_irq_restore(flags);
 163
 164         clockevents_register_device(clk);
 165 }
 166
 167 /*
 168  * take a local timer down
 169  */
 170 void __cpuexit twd_timer_stop(void)
 171 {
 172         __raw_writel(0, twd_base + TWD_TIMER_CONTROL);
 173 }