arch/arm/mach-realview/localtimer.c

   1 /*
   2  *  linux/arch/arm/mach-realview/localtimer.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/percpu.h>
  18 #include <linux/clockchips.h>
  19 #include <linux/irq.h>
  20 #include <linux/io.h>
  21
  22 #include <asm/hardware/arm_twd.h>
  23 #include <asm/hardware/gic.h>
  24 #include <mach/hardware.h>
  25 #include <asm/irq.h>
  26
  27 static DEFINE_PER_CPU(struct clock_event_device, local_clockevent);
  28
  29 /*
  30  * Used on SMP for either the local timer or IPI_TIMER
  31  */
  32 void local_timer_interrupt(void)
  33 {
  34         struct clock_event_device *clk = &__get_cpu_var(local_clockevent);
  35
  36         clk->event_handler(clk);
  37 }
  38
  39 #ifdef CONFIG_LOCAL_TIMERS
  40
  41 /* set up by the platform code */
  42 void __iomem *twd_base;
  43
  44 static unsigned long mpcore_timer_rate;
  45
  46 static void local_timer_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 local_timer_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 local_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 (mpcore_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                 mpcore_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 130
 131                 printk("%lu.%02luMHz.\n", mpcore_timer_rate / 1000000,
 132                         (mpcore_timer_rate / 100000) % 100);
 133         }
 134
 135         load = mpcore_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 local_timer_setup(void)
 144 {
 145         unsigned int cpu = smp_processor_id();
 146         struct clock_event_device *clk = &per_cpu(local_clockevent, cpu);
 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           = local_timer_set_mode;
 155         clk->set_next_event     = local_timer_set_next_event;
 156         clk->irq                = IRQ_LOCALTIMER;
 157         clk->cpumask            = cpumask_of(cpu);
 158         clk->shift              = 20;
 159         clk->mult               = div_sc(mpcore_timer_rate, NSEC_PER_SEC, clk->shift);
 160         clk->max_delta_ns       = clockevent_delta2ns(0xffffffff, clk);
 161         clk->min_delta_ns       = clockevent_delta2ns(0xf, clk);
 162
 163         /* Make sure our local interrupt controller has this enabled */
 164         local_irq_save(flags);
 165         get_irq_chip(IRQ_LOCALTIMER)->unmask(IRQ_LOCALTIMER);
 166         local_irq_restore(flags);
 167
 168         clockevents_register_device(clk);
 169 }
 170
 171 /*
 172  * take a local timer down
 173  */
 174 void __cpuexit local_timer_stop(void)
 175 {
 176         __raw_writel(0, twd_base + TWD_TIMER_CONTROL);
 177 }
 178
 179 #else   /* CONFIG_LOCAL_TIMERS */
 180
 181 static void dummy_timer_set_mode(enum clock_event_mode mode,
 182                                  struct clock_event_device *clk)
 183 {
 184 }
 185
 186 void __cpuinit local_timer_setup(void)
 187 {
 188         unsigned int cpu = smp_processor_id();
 189         struct clock_event_device *clk = &per_cpu(local_clockevent, cpu);
 190
 191         clk->name               = "dummy_timer";
 192         clk->features           = CLOCK_EVT_FEAT_DUMMY;
 193         clk->rating             = 200;
 194         clk->set_mode           = dummy_timer_set_mode;
 195         clk->broadcast          = smp_timer_broadcast;
 196         clk->cpumask            = cpumask_of(cpu);
 197
 198         clockevents_register_device(clk);
 199 }
 200
 201 #endif  /* !CONFIG_LOCAL_TIMERS */