drivers/acpi/hardware/hwtimer.c

   1
   2 /******************************************************************************
   3  *
   4  * Name: hwtimer.c - ACPI Power Management Timer Interface
   5  *
   6  *****************************************************************************/
   7
   8 /*
   9  * Copyright (C) 2000 - 2004, R. Byron Moore
  10  * All rights reserved.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, this list of conditions, and the following disclaimer,
  17  *    without modification.
  18  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
  19  *    substantially similar to the "NO WARRANTY" disclaimer below
  20  *    ("Disclaimer") and any redistribution must be conditioned upon
  21  *    including a substantially similar Disclaimer requirement for further
  22  *    binary redistribution.
  23  * 3. Neither the names of the above-listed copyright holders nor the names
  24  *    of any contributors may be used to endorse or promote products derived
  25  *    from this software without specific prior written permission.
  26  *
  27  * Alternatively, this software may be distributed under the terms of the
  28  * GNU General Public License ("GPL") version 2 as published by the Free
  29  * Software Foundation.
  30  *
  31  * NO WARRANTY
  32  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  33  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  34  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
  35  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  36  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  37  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  38  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  39  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  40  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  41  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  42  * POSSIBILITY OF SUCH DAMAGES.
  43  */
  44
  45 #include <acpi/acpi.h>
  46
  47 #define _COMPONENT          ACPI_HARDWARE
  48          ACPI_MODULE_NAME    ("hwtimer")
  49
  50
  51 /******************************************************************************
  52  *
  53  * FUNCTION:    acpi_get_timer_resolution
  54  *
  55  * PARAMETERS:  none
  56  *
  57  * RETURN:      Number of bits of resolution in the PM Timer (24 or 32).
  58  *
  59  * DESCRIPTION: Obtains resolution of the ACPI PM Timer.
  60  *
  61  ******************************************************************************/
  62
  63 acpi_status
  64 acpi_get_timer_resolution (
  65         u32                             *resolution)
  66 {
  67         ACPI_FUNCTION_TRACE ("acpi_get_timer_resolution");
  68
  69
  70         if (!resolution) {
  71                 return_ACPI_STATUS (AE_BAD_PARAMETER);
  72         }
  73
  74         if (0 == acpi_gbl_FADT->tmr_val_ext) {
  75                 *resolution = 24;
  76         }
  77         else {
  78                 *resolution = 32;
  79         }
  80
  81         return_ACPI_STATUS (AE_OK);
  82 }
  83
  84
  85 /******************************************************************************
  86  *
  87  * FUNCTION:    acpi_get_timer
  88  *
  89  * PARAMETERS:  none
  90  *
  91  * RETURN:      Current value of the ACPI PM Timer (in ticks).
  92  *
  93  * DESCRIPTION: Obtains current value of ACPI PM Timer.
  94  *
  95  ******************************************************************************/
  96
  97 acpi_status
  98 acpi_get_timer (
  99         u32                             *ticks)
 100 {
 101         acpi_status                     status;
 102
 103
 104         ACPI_FUNCTION_TRACE ("acpi_get_timer");
 105
 106
 107         if (!ticks) {
 108                 return_ACPI_STATUS (AE_BAD_PARAMETER);
 109         }
 110
 111         status = acpi_hw_low_level_read (32, ticks, &acpi_gbl_FADT->xpm_tmr_blk);
 112
 113         return_ACPI_STATUS (status);
 114 }
 115
 116
 117 /******************************************************************************
 118  *
 119  * FUNCTION:    acpi_get_timer_duration
 120  *
 121  * PARAMETERS:  start_ticks
 122  *              end_ticks
 123  *              time_elapsed
 124  *
 125  * RETURN:      time_elapsed
 126  *
 127  * DESCRIPTION: Computes the time elapsed (in microseconds) between two
 128  *              PM Timer time stamps, taking into account the possibility of
 129  *              rollovers, the timer resolution, and timer frequency.
 130  *
 131  *              The PM Timer's clock ticks at roughly 3.6 times per
 132  *              _microsecond_, and its clock continues through Cx state
 133  *              transitions (unlike many CPU timestamp counters) -- making it
 134  *              a versatile and accurate timer.
 135  *
 136  *              Note that this function accommodates only a single timer
 137  *              rollover.  Thus for 24-bit timers, this function should only
 138  *              be used for calculating durations less than ~4.6 seconds
 139  *              (~20 minutes for 32-bit timers) -- calculations below
 140  *
 141  *              2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
 142  *              2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
 143  *
 144  ******************************************************************************/
 145
 146 acpi_status
 147 acpi_get_timer_duration (
 148         u32                             start_ticks,
 149         u32                             end_ticks,
 150         u32                             *time_elapsed)
 151 {
 152         u32                             delta_ticks = 0;
 153         union uint64_overlay            normalized_ticks;
 154         acpi_status                     status;
 155         acpi_integer                    out_quotient;
 156
 157
 158         ACPI_FUNCTION_TRACE ("acpi_get_timer_duration");
 159
 160
 161         if (!time_elapsed) {
 162                 return_ACPI_STATUS (AE_BAD_PARAMETER);
 163         }
 164
 165         /*
 166          * Compute Tick Delta:
 167          * -------------------
 168          * Handle (max one) timer rollovers on 24- versus 32-bit timers.
 169          */
 170         if (start_ticks < end_ticks) {
 171                 delta_ticks = end_ticks - start_ticks;
 172         }
 173         else if (start_ticks > end_ticks) {
 174                 if (0 == acpi_gbl_FADT->tmr_val_ext) {
 175                         /* 24-bit Timer */
 176
 177                         delta_ticks = (((0x00FFFFFF - start_ticks) + end_ticks) & 0x00FFFFFF);
 178                 }
 179                 else {
 180                         /* 32-bit Timer */
 181
 182                         delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
 183                 }
 184         }
 185         else {
 186                 *time_elapsed = 0;
 187                 return_ACPI_STATUS (AE_OK);
 188         }
 189
 190         /*
 191          * Compute Duration:
 192          * -----------------
 193          *
 194          * Requires a 64-bit divide:
 195          *
 196          * time_elapsed = (delta_ticks * 1000000) / PM_TIMER_FREQUENCY;
 197          */
 198         normalized_ticks.full = ((u64) delta_ticks) * 1000000;
 199
 200         status = acpi_ut_short_divide (&normalized_ticks.full, PM_TIMER_FREQUENCY,
 201                            &out_quotient, NULL);
 202
 203         *time_elapsed = (u32) out_quotient;
 204         return_ACPI_STATUS (status);
 205 }
 206
 207