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 - 2006, 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 <linux/module.h>
  46 #include <acpi/acpi.h>
  47
  48 #define _COMPONENT          ACPI_HARDWARE
  49 ACPI_MODULE_NAME("hwtimer")
  50
  51 /******************************************************************************
  52  *
  53  * FUNCTION:    acpi_get_timer_resolution
  54  *
  55  * PARAMETERS:  Resolution          - Where the resolution is returned
  56  *
  57  * RETURN:      Status and timer resolution
  58  *
  59  * DESCRIPTION: Obtains resolution of the ACPI PM Timer (24 or 32 bits).
  60  *
  61  ******************************************************************************/
  62 acpi_status acpi_get_timer_resolution(u32 * resolution)
  63 {
  64         ACPI_FUNCTION_TRACE("acpi_get_timer_resolution");
  65
  66         if (!resolution) {
  67                 return_ACPI_STATUS(AE_BAD_PARAMETER);
  68         }
  69
  70         if (0 == acpi_gbl_FADT->tmr_val_ext) {
  71                 *resolution = 24;
  72         } else {
  73                 *resolution = 32;
  74         }
  75
  76         return_ACPI_STATUS(AE_OK);
  77 }
  78
  79 /******************************************************************************
  80  *
  81  * FUNCTION:    acpi_get_timer
  82  *
  83  * PARAMETERS:  Ticks               - Where the timer value is returned
  84  *
  85  * RETURN:      Status and current timer value (ticks)
  86  *
  87  * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
  88  *
  89  ******************************************************************************/
  90
  91 acpi_status acpi_get_timer(u32 * ticks)
  92 {
  93         acpi_status status;
  94
  95         ACPI_FUNCTION_TRACE("acpi_get_timer");
  96
  97         if (!ticks) {
  98                 return_ACPI_STATUS(AE_BAD_PARAMETER);
  99         }
 100
 101         status = acpi_hw_low_level_read(32, ticks, &acpi_gbl_FADT->xpm_tmr_blk);
 102
 103         return_ACPI_STATUS(status);
 104 }
 105
 106 EXPORT_SYMBOL(acpi_get_timer);
 107
 108 /******************************************************************************
 109  *
 110  * FUNCTION:    acpi_get_timer_duration
 111  *
 112  * PARAMETERS:  start_ticks         - Starting timestamp
 113  *              end_ticks           - End timestamp
 114  *              time_elapsed        - Where the elapsed time is returned
 115  *
 116  * RETURN:      Status and time_elapsed
 117  *
 118  * DESCRIPTION: Computes the time elapsed (in microseconds) between two
 119  *              PM Timer time stamps, taking into account the possibility of
 120  *              rollovers, the timer resolution, and timer frequency.
 121  *
 122  *              The PM Timer's clock ticks at roughly 3.6 times per
 123  *              _microsecond_, and its clock continues through Cx state
 124  *              transitions (unlike many CPU timestamp counters) -- making it
 125  *              a versatile and accurate timer.
 126  *
 127  *              Note that this function accommodates only a single timer
 128  *              rollover.  Thus for 24-bit timers, this function should only
 129  *              be used for calculating durations less than ~4.6 seconds
 130  *              (~20 minutes for 32-bit timers) -- calculations below:
 131  *
 132  *              2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
 133  *              2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
 134  *
 135  ******************************************************************************/
 136
 137 acpi_status
 138 acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 * time_elapsed)
 139 {
 140         acpi_status status;
 141         u32 delta_ticks;
 142         acpi_integer quotient;
 143
 144         ACPI_FUNCTION_TRACE("acpi_get_timer_duration");
 145
 146         if (!time_elapsed) {
 147                 return_ACPI_STATUS(AE_BAD_PARAMETER);
 148         }
 149
 150         /*
 151          * Compute Tick Delta:
 152          * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
 153          */
 154         if (start_ticks < end_ticks) {
 155                 delta_ticks = end_ticks - start_ticks;
 156         } else if (start_ticks > end_ticks) {
 157                 if (0 == acpi_gbl_FADT->tmr_val_ext) {
 158
 159                         /* 24-bit Timer */
 160
 161                         delta_ticks =
 162                             (((0x00FFFFFF - start_ticks) +
 163                               end_ticks) & 0x00FFFFFF);
 164                 } else {
 165                         /* 32-bit Timer */
 166
 167                         delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
 168                 }
 169         } else {                /* start_ticks == end_ticks */
 170
 171                 *time_elapsed = 0;
 172                 return_ACPI_STATUS(AE_OK);
 173         }
 174
 175         /*
 176          * Compute Duration (Requires a 64-bit multiply and divide):
 177          *
 178          * time_elapsed = (delta_ticks * 1000000) / PM_TIMER_FREQUENCY;
 179          */
 180         status = acpi_ut_short_divide(((u64) delta_ticks) * 1000000,
 181                                       PM_TIMER_FREQUENCY, &quotient, NULL);
 182
 183         *time_elapsed = (u32) quotient;
 184         return_ACPI_STATUS(status);
 185 }
 186
 187 EXPORT_SYMBOL(acpi_get_timer_duration);