common/clock.c

   1 /*
   2  * clock.c - generic clocksource implementation
   3  *
   4  * This file contains the clocksource implementation from the Linux
   5  * kernel originally by John Stultz
   6  *
   7  * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
   8  * Copyright (c) 2007 Sascha Hauer <s.hauer@pengutronix.de>, Pengutronix
   9  *
  10  * See file CREDITS for list of people who contributed to this
  11  * project.
  12  *
  13  * This program is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU General Public License version 2
  15  * as published by the Free Software Foundation.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  25  */
  26
  27 #include <common.h>
  28 #include <asm-generic/div64.h>
  29 #include <clock.h>
  30
  31 static struct clocksource *current_clock;
  32 static uint64_t time_ns;
  33
  34 /**
  35  * get_time_ns - get current timestamp in nanoseconds
  36  */
  37 uint64_t get_time_ns(void)
  38 {
  39         struct clocksource *cs = current_clock;
  40         uint64_t cycle_now, cycle_delta;
  41         uint64_t ns_offset;
  42
  43         /* read clocksource: */
  44         cycle_now = cs->read() & cs->mask;
  45
  46         /* calculate the delta since the last call: */
  47         cycle_delta = (cycle_now - cs->cycle_last) & cs->mask;
  48
  49         /* convert to nanoseconds: */
  50         ns_offset = cyc2ns(cs, cycle_delta);
  51
  52         cs->cycle_last = cycle_now;
  53
  54         time_ns += ns_offset;
  55         return time_ns;
  56 }
  57 EXPORT_SYMBOL(get_time_ns);
  58
  59 /**
  60  * clocksource_hz2mult - calculates mult from hz and shift
  61  * @hz:                 Clocksource frequency in Hz
  62  * @shift_constant:     Clocksource shift factor
  63  *
  64  * Helper functions that converts a hz counter
  65  * frequency to a timsource multiplier, given the
  66  * clocksource shift value
  67  */
  68 uint32_t clocksource_hz2mult(uint32_t hz, uint32_t shift_constant)
  69 {
  70         /*  hz = cyc/(Billion ns)
  71          *  mult/2^shift  = ns/cyc
  72          *  mult = ns/cyc * 2^shift
  73          *  mult = 1Billion/hz * 2^shift
  74          *  mult = 1000000000 * 2^shift / hz
  75          *  mult = (1000000000<<shift) / hz
  76          */
  77         uint64_t tmp = ((uint64_t)1000000000) << shift_constant;
  78
  79         tmp += hz/2; /* round for do_div */
  80         do_div(tmp, hz);
  81
  82         return (uint32_t)tmp;
  83 }
  84
  85 int is_timeout(uint64_t start_ns, uint64_t time_offset_ns)
  86 {
  87
  88         if (start_ns + time_offset_ns < get_time_ns())
  89                 return 1;
  90         else
  91                 return 0;
  92 }
  93 EXPORT_SYMBOL(is_timeout);
  94
  95 void ndelay(unsigned long nsecs)
  96 {
  97         uint64_t start = get_time_ns();
  98
  99         while(!is_timeout(start, nsecs));
 100 }
 101 EXPORT_SYMBOL(ndelay);
 102
 103 void udelay(unsigned long usecs)
 104 {
 105         uint64_t start = get_time_ns();
 106
 107         while(!is_timeout(start, usecs * 1000));
 108 }
 109 EXPORT_SYMBOL(udelay);
 110
 111 void mdelay(unsigned long msecs)
 112 {
 113         uint64_t start = get_time_ns();
 114
 115         while(!is_timeout(start, msecs * 1000000));
 116 }
 117 EXPORT_SYMBOL(mdelay);
 118
 119 int init_clock(struct clocksource *cs)
 120 {
 121         current_clock = cs;
 122         return 0;
 123 }