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/localtimer.h>
  23 #include <asm/hardware/gic.h>
  24
  25 /* set up by the platform code */
  26 void __iomem *twd_base;
  27
  28 static unsigned long twd_timer_rate;
  29
  30 static struct clock_event_device __percpu **twd_evt;
  31
  32 static void twd_set_mode(enum clock_event_mode mode,
  33                         struct clock_event_device *clk)
  34 {
  35         unsigned long ctrl;
  36
  37         switch (mode) {
  38         case CLOCK_EVT_MODE_PERIODIC:
  39                 /* timer load already set up */
  40                 ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
  41                         | TWD_TIMER_CONTROL_PERIODIC;
  42                 __raw_writel(twd_timer_rate / HZ, twd_base + TWD_TIMER_LOAD);
  43                 break;
  44         case CLOCK_EVT_MODE_ONESHOT:
  45                 /* period set, and timer enabled in 'next_event' hook */
  46                 ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT;
  47                 break;
  48         case CLOCK_EVT_MODE_UNUSED:
  49         case CLOCK_EVT_MODE_SHUTDOWN:
  50         default:
  51                 ctrl = 0;
  52         }
  53
  54         __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
  55 }
  56
  57 static int twd_set_next_event(unsigned long evt,
  58                         struct clock_event_device *unused)
  59 {
  60         unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL);
  61
  62         ctrl |= TWD_TIMER_CONTROL_ENABLE;
  63
  64         __raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
  65         __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
  66
  67         return 0;
  68 }
  69
  70 /*
  71  * local_timer_ack: checks for a local timer interrupt.
  72  *
  73  * If a local timer interrupt has occurred, acknowledge and return 1.
  74  * Otherwise, return 0.
  75  */
  76 int twd_timer_ack(void)
  77 {
  78         if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
  79                 __raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
  80                 return 1;
  81         }
  82
  83         return 0;
  84 }
  85
  86 void twd_timer_stop(struct clock_event_device *clk)
  87 {
  88         twd_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
  89         disable_percpu_irq(clk->irq);
  90 }
  91
  92 static void __cpuinit twd_calibrate_rate(void)
  93 {
  94         unsigned long count;
  95         u64 waitjiffies;
  96
  97         /*
  98          * If this is the first time round, we need to work out how fast
  99          * the timer ticks
 100          */
 101         if (twd_timer_rate == 0) {
 102                 printk(KERN_INFO "Calibrating local timer... ");
 103
 104                 /* Wait for a tick to start */
 105                 waitjiffies = get_jiffies_64() + 1;
 106
 107                 while (get_jiffies_64() < waitjiffies)
 108                         udelay(10);
 109
 110                 /* OK, now the tick has started, let's get the timer going */
 111                 waitjiffies += 5;
 112
 113                                  /* enable, no interrupt or reload */
 114                 __raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
 115
 116                                  /* maximum value */
 117                 __raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
 118
 119                 while (get_jiffies_64() < waitjiffies)
 120                         udelay(10);
 121
 122                 count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
 123
 124                 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 125
 126                 printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 127                         (twd_timer_rate / 10000) % 100);
 128         }
 129 }
 130
 131 static irqreturn_t twd_handler(int irq, void *dev_id)
 132 {
 133         struct clock_event_device *evt = *(struct clock_event_device **)dev_id;
 134
 135         if (twd_timer_ack()) {
 136                 evt->event_handler(evt);
 137                 return IRQ_HANDLED;
 138         }
 139
 140         return IRQ_NONE;
 141 }
 142
 143 /*
 144  * Setup the local clock events for a CPU.
 145  */
 146 void __cpuinit twd_timer_setup(struct clock_event_device *clk)
 147 {
 148         struct clock_event_device **this_cpu_clk;
 149
 150         if (!twd_evt) {
 151                 int err;
 152
 153                 twd_evt = alloc_percpu(struct clock_event_device *);
 154                 if (!twd_evt) {
 155                         pr_err("twd: can't allocate memory\n");
 156                         return;
 157                 }
 158
 159                 err = request_percpu_irq(clk->irq, twd_handler,
 160                                          "twd", twd_evt);
 161                 if (err) {
 162                         pr_err("twd: can't register interrupt %d (%d)\n",
 163                                clk->irq, err);
 164                         return;
 165                 }
 166         }
 167
 168         twd_calibrate_rate();
 169
 170         clk->name = "local_timer";
 171         clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
 172                         CLOCK_EVT_FEAT_C3STOP;
 173         clk->rating = 350;
 174         clk->set_mode = twd_set_mode;
 175         clk->set_next_event = twd_set_next_event;
 176         clk->shift = 20;
 177         clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
 178         clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
 179         clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
 180
 181         this_cpu_clk = __this_cpu_ptr(twd_evt);
 182         *this_cpu_clk = clk;
 183
 184         clockevents_register_device(clk);
 185
 186         enable_percpu_irq(clk->irq, 0);
 187 }