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 /* set up by the platform code */
  25 void __iomem *twd_base;
  26
  27 static unsigned long twd_timer_rate;
  28
  29 static 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                 break;
  40         case CLOCK_EVT_MODE_ONESHOT:
  41                 /* period set, and timer enabled in 'next_event' hook */
  42                 ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT;
  43                 break;
  44         case CLOCK_EVT_MODE_UNUSED:
  45         case CLOCK_EVT_MODE_SHUTDOWN:
  46         default:
  47                 ctrl = 0;
  48         }
  49
  50         __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
  51 }
  52
  53 static int twd_set_next_event(unsigned long evt,
  54                         struct clock_event_device *unused)
  55 {
  56         unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL);
  57
  58         ctrl |= TWD_TIMER_CONTROL_ENABLE;
  59
  60         __raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
  61         __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
  62
  63         return 0;
  64 }
  65
  66 /*
  67  * local_timer_ack: checks for a local timer interrupt.
  68  *
  69  * If a local timer interrupt has occurred, acknowledge and return 1.
  70  * Otherwise, return 0.
  71  */
  72 int twd_timer_ack(void)
  73 {
  74         if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
  75                 __raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
  76                 return 1;
  77         }
  78
  79         return 0;
  80 }
  81
  82 static void __cpuinit twd_calibrate_rate(void)
  83 {
  84         unsigned long load, count;
  85         u64 waitjiffies;
  86
  87         /*
  88          * If this is the first time round, we need to work out how fast
  89          * the timer ticks
  90          */
  91         if (twd_timer_rate == 0) {
  92                 printk(KERN_INFO "Calibrating local timer... ");
  93
  94                 /* Wait for a tick to start */
  95                 waitjiffies = get_jiffies_64() + 1;
  96
  97                 while (get_jiffies_64() < waitjiffies)
  98                         udelay(10);
  99
 100                 /* OK, now the tick has started, let's get the timer going */
 101                 waitjiffies += 5;
 102
 103                                  /* enable, no interrupt or reload */
 104                 __raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
 105
 106                                  /* maximum value */
 107                 __raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
 108
 109                 while (get_jiffies_64() < waitjiffies)
 110                         udelay(10);
 111
 112                 count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
 113
 114                 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 115
 116                 printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 117                         (twd_timer_rate / 100000) % 100);
 118         }
 119
 120         load = twd_timer_rate / HZ;
 121
 122         __raw_writel(load, twd_base + TWD_TIMER_LOAD);
 123 }
 124
 125 /*
 126  * Setup the local clock events for a CPU.
 127  */
 128 void __cpuinit twd_timer_setup(struct clock_event_device *clk)
 129 {
 130         unsigned long flags;
 131
 132         twd_calibrate_rate();
 133
 134         clk->name = "local_timer";
 135         clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
 136                         CLOCK_EVT_FEAT_C3STOP;
 137         clk->rating = 350;
 138         clk->set_mode = twd_set_mode;
 139         clk->set_next_event = twd_set_next_event;
 140         clk->shift = 20;
 141         clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
 142         clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
 143         clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
 144
 145         /* Make sure our local interrupt controller has this enabled */
 146         local_irq_save(flags);
 147         irq_to_desc(clk->irq)->status |= IRQ_NOPROBE;
 148         get_irq_chip(clk->irq)->unmask(clk->irq);
 149         local_irq_restore(flags);
 150
 151         clockevents_register_device(clk);
 152 }
 153
 154 #ifdef CONFIG_HOTPLUG_CPU
 155 /*
 156  * take a local timer down
 157  */
 158 void twd_timer_stop(void)
 159 {
 160         __raw_writel(0, twd_base + TWD_TIMER_CONTROL);
 161 }
 162 #endif