arch/xtensa/kernel/time.c

   1 /*
   2  * arch/xtensa/kernel/time.c
   3  *
   4  * Timer and clock support.
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License.  See the file "COPYING" in the main directory of this archive
   8  * for more details.
   9  *
  10  * Copyright (C) 2005 Tensilica Inc.
  11  *
  12  * Chris Zankel <chris@zankel.net>
  13  */
  14
  15 #include <linux/errno.h>
  16 #include <linux/sched.h>
  17 #include <linux/time.h>
  18 #include <linux/clocksource.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/module.h>
  21 #include <linux/init.h>
  22 #include <linux/irq.h>
  23 #include <linux/profile.h>
  24 #include <linux/delay.h>
  25
  26 #include <asm/timex.h>
  27 #include <asm/platform.h>
  28
  29 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  30 unsigned long ccount_per_jiffy;         /* per 1/HZ */
  31 unsigned long nsec_per_ccount;          /* nsec per ccount increment */
  32 #endif
  33
  34 static cycle_t ccount_read(void)
  35 {
  36         return (cycle_t)get_ccount();
  37 }
  38
  39 static struct clocksource ccount_clocksource = {
  40         .name = "ccount",
  41         .rating = 200,
  42         .read = ccount_read,
  43         .mask = CLOCKSOURCE_MASK(32),
  44 };
  45
  46 static irqreturn_t timer_interrupt(int irq, void *dev_id);
  47 static struct irqaction timer_irqaction = {
  48         .handler =      timer_interrupt,
  49         .flags =        IRQF_DISABLED,
  50         .name =         "timer",
  51 };
  52
  53 void __init time_init(void)
  54 {
  55 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  56         printk("Calibrating CPU frequency ");
  57         platform_calibrate_ccount();
  58         printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),
  59                         (int)(ccount_per_jiffy/(10000/HZ))%100);
  60 #endif
  61         clocksource_register_hz(&ccount_clocksource, CCOUNT_PER_JIFFY * HZ);
  62
  63         /* Initialize the linux timer interrupt. */
  64
  65         setup_irq(LINUX_TIMER_INT, &timer_irqaction);
  66         set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
  67 }
  68
  69 /*
  70  * The timer interrupt is called HZ times per second.
  71  */
  72
  73 irqreturn_t timer_interrupt (int irq, void *dev_id)
  74 {
  75
  76         unsigned long next;
  77
  78         next = get_linux_timer();
  79
  80 again:
  81         while ((signed long)(get_ccount() - next) > 0) {
  82
  83                 profile_tick(CPU_PROFILING);
  84 #ifndef CONFIG_SMP
  85                 update_process_times(user_mode(get_irq_regs()));
  86 #endif
  87
  88                 xtime_update(1); /* Linux handler in kernel/time/timekeeping */
  89
  90                 /* Note that writing CCOMPARE clears the interrupt. */
  91
  92                 next += CCOUNT_PER_JIFFY;
  93                 set_linux_timer(next);
  94         }
  95
  96         /* Allow platform to do something useful (Wdog). */
  97
  98         platform_heartbeat();
  99
 100         /* Make sure we didn't miss any tick... */
 101
 102         if ((signed long)(get_ccount() - next) > 0)
 103                 goto again;
 104
 105         return IRQ_HANDLED;
 106 }
 107
 108 #ifndef CONFIG_GENERIC_CALIBRATE_DELAY
 109 void __cpuinit calibrate_delay(void)
 110 {
 111         loops_per_jiffy = CCOUNT_PER_JIFFY;
 112         printk("Calibrating delay loop (skipped)... "
 113                "%lu.%02lu BogoMIPS preset\n",
 114                loops_per_jiffy/(1000000/HZ),
 115                (loops_per_jiffy/(10000/HZ)) % 100);
 116 }
 117 #endif