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         /* FIXME: xtime&wall_to_monotonic are set in timekeeping_init. */
  63         read_persistent_clock(&xtime);
  64         set_normalized_timespec(&wall_to_monotonic,
  65                 -xtime.tv_sec, -xtime.tv_nsec);
  66
  67 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  68         printk("Calibrating CPU frequency ");
  69         platform_calibrate_ccount();
  70         printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),
  71                         (int)(ccount_per_jiffy/(10000/HZ))%100);
  72 #endif
  73         ccount_clocksource.mult =
  74                 clocksource_hz2mult(CCOUNT_PER_JIFFY * HZ,
  75                                 ccount_clocksource.shift);
  76         clocksource_register(&ccount_clocksource);
  77
  78         /* Initialize the linux timer interrupt. */
  79
  80         setup_irq(LINUX_TIMER_INT, &timer_irqaction);
  81         set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
  82 }
  83
  84 /*
  85  * The timer interrupt is called HZ times per second.
  86  */
  87
  88 irqreturn_t timer_interrupt (int irq, void *dev_id)
  89 {
  90
  91         unsigned long next;
  92
  93         next = get_linux_timer();
  94
  95 again:
  96         while ((signed long)(get_ccount() - next) > 0) {
  97
  98                 profile_tick(CPU_PROFILING);
  99 #ifndef CONFIG_SMP
 100                 update_process_times(user_mode(get_irq_regs()));
 101 #endif
 102
 103                 write_seqlock(&xtime_lock);
 104
 105                 do_timer(1); /* Linux handler in kernel/timer.c */
 106
 107                 /* Note that writing CCOMPARE clears the interrupt. */
 108
 109                 next += CCOUNT_PER_JIFFY;
 110                 set_linux_timer(next);
 111
 112                 write_sequnlock(&xtime_lock);
 113         }
 114
 115         /* Allow platform to do something useful (Wdog). */
 116
 117         platform_heartbeat();
 118
 119         /* Make sure we didn't miss any tick... */
 120
 121         if ((signed long)(get_ccount() - next) > 0)
 122                 goto again;
 123
 124         return IRQ_HANDLED;
 125 }
 126
 127 #ifndef CONFIG_GENERIC_CALIBRATE_DELAY
 128 void __cpuinit calibrate_delay(void)
 129 {
 130         loops_per_jiffy = CCOUNT_PER_JIFFY;
 131         printk("Calibrating delay loop (skipped)... "
 132                "%lu.%02lu BogoMIPS preset\n",
 133                loops_per_jiffy/(1000000/HZ),
 134                (loops_per_jiffy/(10000/HZ)) % 100);
 135 }
 136 #endif