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