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/clk.h>
  14 #include <linux/delay.h>
  15 #include <linux/device.h>
  16 #include <linux/err.h>
  17 #include <linux/smp.h>
  18 #include <linux/jiffies.h>
  19 #include <linux/clockchips.h>
  20 #include <linux/irq.h>
  21 #include <linux/io.h>
  22
  23 #include <asm/smp_twd.h>
  24 #include <asm/localtimer.h>
  25 #include <asm/hardware/gic.h>
  26
  27 /* set up by the platform code */
  28 void __iomem *twd_base;
  29
  30 static struct clk *twd_clk;
  31 static unsigned long twd_timer_rate;
  32
  33 static struct clock_event_device __percpu **twd_evt;
  34
  35 static void twd_set_mode(enum clock_event_mode mode,
  36                         struct clock_event_device *clk)
  37 {
  38         unsigned long ctrl;
  39
  40         switch (mode) {
  41         case CLOCK_EVT_MODE_PERIODIC:
  42                 /* timer load already set up */
  43                 ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
  44                         | TWD_TIMER_CONTROL_PERIODIC;
  45                 __raw_writel(twd_timer_rate / HZ, twd_base + TWD_TIMER_LOAD);
  46                 break;
  47         case CLOCK_EVT_MODE_ONESHOT:
  48                 /* period set, and timer enabled in 'next_event' hook */
  49                 ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT;
  50                 break;
  51         case CLOCK_EVT_MODE_UNUSED:
  52         case CLOCK_EVT_MODE_SHUTDOWN:
  53         default:
  54                 ctrl = 0;
  55         }
  56
  57         __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
  58 }
  59
  60 static int twd_set_next_event(unsigned long evt,
  61                         struct clock_event_device *unused)
  62 {
  63         unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL);
  64
  65         ctrl |= TWD_TIMER_CONTROL_ENABLE;
  66
  67         __raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
  68         __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
  69
  70         return 0;
  71 }
  72
  73 /*
  74  * local_timer_ack: checks for a local timer interrupt.
  75  *
  76  * If a local timer interrupt has occurred, acknowledge and return 1.
  77  * Otherwise, return 0.
  78  */
  79 int twd_timer_ack(void)
  80 {
  81         if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
  82                 __raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
  83                 return 1;
  84         }
  85
  86         return 0;
  87 }
  88
  89 void twd_timer_stop(struct clock_event_device *clk)
  90 {
  91         twd_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
  92         disable_percpu_irq(clk->irq);
  93 }
  94
  95 static void __cpuinit twd_calibrate_rate(void)
  96 {
  97         unsigned long count;
  98         u64 waitjiffies;
  99
 100         /*
 101          * If this is the first time round, we need to work out how fast
 102          * the timer ticks
 103          */
 104         if (twd_timer_rate == 0) {
 105                 printk(KERN_INFO "Calibrating local timer... ");
 106
 107                 /* Wait for a tick to start */
 108                 waitjiffies = get_jiffies_64() + 1;
 109
 110                 while (get_jiffies_64() < waitjiffies)
 111                         udelay(10);
 112
 113                 /* OK, now the tick has started, let's get the timer going */
 114                 waitjiffies += 5;
 115
 116                                  /* enable, no interrupt or reload */
 117                 __raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
 118
 119                                  /* maximum value */
 120                 __raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
 121
 122                 while (get_jiffies_64() < waitjiffies)
 123                         udelay(10);
 124
 125                 count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
 126
 127                 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 128
 129                 printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 130                         (twd_timer_rate / 10000) % 100);
 131         }
 132 }
 133
 134 static irqreturn_t twd_handler(int irq, void *dev_id)
 135 {
 136         struct clock_event_device *evt = *(struct clock_event_device **)dev_id;
 137
 138         if (twd_timer_ack()) {
 139                 evt->event_handler(evt);
 140                 return IRQ_HANDLED;
 141         }
 142
 143         return IRQ_NONE;
 144 }
 145
 146 static struct clk *twd_get_clock(void)
 147 {
 148         struct clk *clk;
 149         int err;
 150
 151         clk = clk_get_sys("smp_twd", NULL);
 152         if (IS_ERR(clk)) {
 153                 pr_err("smp_twd: clock not found: %d\n", (int)PTR_ERR(clk));
 154                 return clk;
 155         }
 156
 157         err = clk_prepare(clk);
 158         if (err) {
 159                 pr_err("smp_twd: clock failed to prepare: %d\n", err);
 160                 clk_put(clk);
 161                 return ERR_PTR(err);
 162         }
 163
 164         err = clk_enable(clk);
 165         if (err) {
 166                 pr_err("smp_twd: clock failed to enable: %d\n", err);
 167                 clk_unprepare(clk);
 168                 clk_put(clk);
 169                 return ERR_PTR(err);
 170         }
 171
 172         return clk;
 173 }
 174
 175 /*
 176  * Setup the local clock events for a CPU.
 177  */
 178 void __cpuinit twd_timer_setup(struct clock_event_device *clk)
 179 {
 180         struct clock_event_device **this_cpu_clk;
 181
 182         if (!twd_evt) {
 183                 int err;
 184
 185                 twd_evt = alloc_percpu(struct clock_event_device *);
 186                 if (!twd_evt) {
 187                         pr_err("twd: can't allocate memory\n");
 188                         return;
 189                 }
 190
 191                 err = request_percpu_irq(clk->irq, twd_handler,
 192                                          "twd", twd_evt);
 193                 if (err) {
 194                         pr_err("twd: can't register interrupt %d (%d)\n",
 195                                clk->irq, err);
 196                         return;
 197                 }
 198         }
 199
 200         if (!twd_clk)
 201                 twd_clk = twd_get_clock();
 202
 203         if (!IS_ERR_OR_NULL(twd_clk))
 204                 twd_timer_rate = clk_get_rate(twd_clk);
 205         else
 206                 twd_calibrate_rate();
 207
 208         clk->name = "local_timer";
 209         clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
 210                         CLOCK_EVT_FEAT_C3STOP;
 211         clk->rating = 350;
 212         clk->set_mode = twd_set_mode;
 213         clk->set_next_event = twd_set_next_event;
 214
 215         this_cpu_clk = __this_cpu_ptr(twd_evt);
 216         *this_cpu_clk = clk;
 217
 218         clockevents_config_and_register(clk, twd_timer_rate,
 219                                         0xf, 0xffffffff);
 220         enable_percpu_irq(clk->irq, 0);
 221 }