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         ctrl |= TWD_TIMER_CONTROL_ENABLE;
  76
  77         __raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
  78         __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
  79
  80         return 0;
  81 }
  82
  83 /*
  84  * local_timer_ack: checks for a local timer interrupt.
  85  *
  86  * If a local timer interrupt has occurred, acknowledge and return 1.
  87  * Otherwise, return 0.
  88  */
  89 int twd_timer_ack(void)
  90 {
  91         if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
  92                 __raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
  93                 return 1;
  94         }
  95
  96         return 0;
  97 }
  98
  99 static void __cpuinit twd_calibrate_rate(void)
 100 {
 101         unsigned long load, count;
 102         u64 waitjiffies;
 103
 104         /*
 105          * If this is the first time round, we need to work out how fast
 106          * the timer ticks
 107          */
 108         if (twd_timer_rate == 0) {
 109                 printk(KERN_INFO "Calibrating local timer... ");
 110
 111                 /* Wait for a tick to start */
 112                 waitjiffies = get_jiffies_64() + 1;
 113
 114                 while (get_jiffies_64() < waitjiffies)
 115                         udelay(10);
 116
 117                 /* OK, now the tick has started, let's get the timer going */
 118                 waitjiffies += 5;
 119
 120                                  /* enable, no interrupt or reload */
 121                 __raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
 122
 123                                  /* maximum value */
 124                 __raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
 125
 126                 while (get_jiffies_64() < waitjiffies)
 127                         udelay(10);
 128
 129                 count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
 130
 131                 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 132
 133                 printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 134                         (twd_timer_rate / 100000) % 100);
 135         }
 136
 137         load = twd_timer_rate / HZ;
 138
 139         __raw_writel(load, twd_base + TWD_TIMER_LOAD);
 140 }
 141
 142 /*
 143  * Setup the local clock events for a CPU.
 144  */
 145 void __cpuinit twd_timer_setup(struct clock_event_device *clk)
 146 {
 147         unsigned long flags;
 148
 149         twd_calibrate_rate();
 150
 151         clk->name = "local_timer";
 152         clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
 153         clk->rating = 350;
 154         clk->set_mode = twd_set_mode;
 155         clk->set_next_event = twd_set_next_event;
 156         clk->shift = 20;
 157         clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
 158         clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
 159         clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
 160
 161         /* Make sure our local interrupt controller has this enabled */
 162         local_irq_save(flags);
 163         get_irq_chip(clk->irq)->unmask(clk->irq);
 164         local_irq_restore(flags);
 165
 166         clockevents_register_device(clk);
 167 }
 168
 169 #ifdef CONFIG_HOTPLUG_CPU
 170 /*
 171  * take a local timer down
 172  */
 173 void twd_timer_stop(void)
 174 {
 175         __raw_writel(0, twd_base + TWD_TIMER_CONTROL);
 176 }
 177 #endif