arch/c6x/kernel/time.c

   1 /*
   2  *  Port on Texas Instruments TMS320C6x architecture
   3  *
   4  *  Copyright (C) 2004, 2009, 2010, 2011 Texas Instruments Incorporated
   5  *  Author: Aurelien Jacquiot (aurelien.jacquiot@jaluna.com)
   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
  12 #include <linux/kernel.h>
  13 #include <linux/clocksource.h>
  14 #include <linux/errno.h>
  15 #include <linux/sched.h>
  16 #include <linux/param.h>
  17 #include <linux/string.h>
  18 #include <linux/mm.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/timex.h>
  21 #include <linux/profile.h>
  22
  23 #include <asm/special_insns.h>
  24 #include <asm/timer64.h>
  25
  26 static u32 sched_clock_multiplier;
  27 #define SCHED_CLOCK_SHIFT 16
  28
  29 static cycle_t tsc_read(struct clocksource *cs)
  30 {
  31         return get_cycles();
  32 }
  33
  34 static struct clocksource clocksource_tsc = {
  35         .name           = "timestamp",
  36         .rating         = 300,
  37         .read           = tsc_read,
  38         .mask           = CLOCKSOURCE_MASK(64),
  39         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  40 };
  41
  42 /*
  43  * scheduler clock - returns current time in nanoseconds.
  44  */
  45 u64 sched_clock(void)
  46 {
  47         u64 tsc = get_cycles();
  48
  49         return (tsc * sched_clock_multiplier) >> SCHED_CLOCK_SHIFT;
  50 }
  51
  52 void __init time_init(void)
  53 {
  54         u64 tmp = (u64)NSEC_PER_SEC << SCHED_CLOCK_SHIFT;
  55
  56         do_div(tmp, c6x_core_freq);
  57         sched_clock_multiplier = tmp;
  58
  59         clocksource_register_hz(&clocksource_tsc, c6x_core_freq);
  60
  61         /* write anything into TSCL to enable counting */
  62         set_creg(TSCL, 0);
  63
  64         /* probe for timer64 event timer */
  65         timer64_init();
  66 }