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/time.h>
  17 #include <linux/clocksource.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/module.h>
  20 #include <linux/init.h>
  21 #include <linux/irq.h>
  22 #include <linux/profile.h>
  23 #include <linux/delay.h>
  24
  25 #include <asm/timex.h>
  26 #include <asm/platform.h>
  27
  28 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  29 unsigned long ccount_per_jiffy;         /* per 1/HZ */
  30 unsigned long nsec_per_ccount;          /* nsec per ccount increment */
  31 #endif
  32
  33 static cycle_t ccount_read(void)
  34 {
  35         return (cycle_t)get_ccount();
  36 }
  37
  38 static struct clocksource ccount_clocksource = {
  39         .name = "ccount",
  40         .rating = 200,
  41         .read = ccount_read,
  42         .mask = CLOCKSOURCE_MASK(32),
  43         /*
  44          * With a shift of 22 the lower limit of the cpu clock is
  45          * 1MHz, where NSEC_PER_CCOUNT is 1000 or a bit less than
  46          * 2^10: Since we have 32 bits and the multiplicator can
  47          * already take up as much as 10 bits, this leaves us with
  48          * remaining upper 22 bits.
  49          */
  50         .shift = 22,
  51 };
  52
  53 static irqreturn_t timer_interrupt(int irq, void *dev_id);
  54 static struct irqaction timer_irqaction = {
  55         .handler =      timer_interrupt,
  56         .flags =        IRQF_DISABLED,
  57         .name =         "timer",
  58 };
  59
  60 void __init time_init(void)
  61 {
  62         xtime.tv_nsec = 0;
  63         xtime.tv_sec = read_persistent_clock();
  64
  65         set_normalized_timespec(&wall_to_monotonic,
  66                 -xtime.tv_sec, -xtime.tv_nsec);
  67
  68 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  69         printk("Calibrating CPU frequency ");
  70         platform_calibrate_ccount();
  71         printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),
  72                         (int)(ccount_per_jiffy/(10000/HZ))%100);
  73 #endif
  74         ccount_clocksource.mult =
  75                 clocksource_hz2mult(CCOUNT_PER_JIFFY * HZ,
  76                                 ccount_clocksource.shift);
  77         clocksource_register(&ccount_clocksource);
  78
  79         /* Initialize the linux timer interrupt. */
  80
  81         setup_irq(LINUX_TIMER_INT, &timer_irqaction);
  82         set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
  83 }
  84
  85 /*
  86  * The timer interrupt is called HZ times per second.
  87  */
  88
  89 irqreturn_t timer_interrupt (int irq, void *dev_id)
  90 {
  91
  92         unsigned long next;
  93
  94         next = get_linux_timer();
  95
  96 again:
  97         while ((signed long)(get_ccount() - next) > 0) {
  98
  99                 profile_tick(CPU_PROFILING);
 100 #ifndef CONFIG_SMP
 101                 update_process_times(user_mode(get_irq_regs()));
 102 #endif
 103
 104                 write_seqlock(&xtime_lock);
 105
 106                 do_timer(1); /* Linux handler in kernel/timer.c */
 107
 108                 /* Note that writing CCOMPARE clears the interrupt. */
 109
 110                 next += CCOUNT_PER_JIFFY;
 111                 set_linux_timer(next);
 112
 113                 write_sequnlock(&xtime_lock);
 114         }
 115
 116         /* Allow platform to do something useful (Wdog). */
 117
 118         platform_heartbeat();
 119
 120         /* Make sure we didn't miss any tick... */
 121
 122         if ((signed long)(get_ccount() - next) > 0)
 123                 goto again;
 124
 125         return IRQ_HANDLED;
 126 }
 127
 128 #ifndef CONFIG_GENERIC_CALIBRATE_DELAY
 129 void __cpuinit calibrate_delay(void)
 130 {
 131         loops_per_jiffy = CCOUNT_PER_JIFFY;
 132         printk("Calibrating delay loop (skipped)... "
 133                "%lu.%02lu BogoMIPS preset\n",
 134                loops_per_jiffy/(1000000/HZ),
 135                (loops_per_jiffy/(10000/HZ)) % 100);
 136 }
 137 #endif