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 - 2005, 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
  47 #include <acpi/acpi.h>
  48
  49 #define _COMPONENT          ACPI_HARDWARE
  50          ACPI_MODULE_NAME    ("hwtimer")
  51
  52
  53 /******************************************************************************
  54  *
  55  * FUNCTION:    acpi_get_timer_resolution
  56  *
  57  * PARAMETERS:  Resolution          - Where the resolution is returned
  58  *
  59  * RETURN:      Status and timer resolution
  60  *
  61  * DESCRIPTION: Obtains resolution of the ACPI PM Timer (24 or 32 bits).
  62  *
  63  ******************************************************************************/
  64
  65 acpi_status
  66 acpi_get_timer_resolution (
  67         u32                             *resolution)
  68 {
  69         ACPI_FUNCTION_TRACE ("acpi_get_timer_resolution");
  70
  71
  72         if (!resolution) {
  73                 return_ACPI_STATUS (AE_BAD_PARAMETER);
  74         }
  75
  76         if (0 == acpi_gbl_FADT->tmr_val_ext) {
  77                 *resolution = 24;
  78         }
  79         else {
  80                 *resolution = 32;
  81         }
  82
  83         return_ACPI_STATUS (AE_OK);
  84 }
  85
  86
  87 /******************************************************************************
  88  *
  89  * FUNCTION:    acpi_get_timer
  90  *
  91  * PARAMETERS:  Ticks               - Where the timer value is returned
  92  *
  93  * RETURN:      Status and current ticks
  94  *
  95  * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
  96  *
  97  ******************************************************************************/
  98
  99 acpi_status
 100 acpi_get_timer (
 101         u32                             *ticks)
 102 {
 103         acpi_status                     status;
 104
 105
 106         ACPI_FUNCTION_TRACE ("acpi_get_timer");
 107
 108
 109         if (!ticks) {
 110                 return_ACPI_STATUS (AE_BAD_PARAMETER);
 111         }
 112
 113         status = acpi_hw_low_level_read (32, ticks, &acpi_gbl_FADT->xpm_tmr_blk);
 114
 115         return_ACPI_STATUS (status);
 116 }
 117 EXPORT_SYMBOL(acpi_get_timer);
 118
 119
 120 /******************************************************************************
 121  *
 122  * FUNCTION:    acpi_get_timer_duration
 123  *
 124  * PARAMETERS:  start_ticks         - Starting timestamp
 125  *              end_ticks           - End timestamp
 126  *              time_elapsed        - Where the elapsed time is returned
 127  *
 128  * RETURN:      Status and time_elapsed
 129  *
 130  * DESCRIPTION: Computes the time elapsed (in microseconds) between two
 131  *              PM Timer time stamps, taking into account the possibility of
 132  *              rollovers, the timer resolution, and timer frequency.
 133  *
 134  *              The PM Timer's clock ticks at roughly 3.6 times per
 135  *              _microsecond_, and its clock continues through Cx state
 136  *              transitions (unlike many CPU timestamp counters) -- making it
 137  *              a versatile and accurate timer.
 138  *
 139  *              Note that this function accommodates only a single timer
 140  *              rollover.  Thus for 24-bit timers, this function should only
 141  *              be used for calculating durations less than ~4.6 seconds
 142  *              (~20 minutes for 32-bit timers) -- calculations below:
 143  *
 144  *              2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
 145  *              2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
 146  *
 147  ******************************************************************************/
 148
 149 acpi_status
 150 acpi_get_timer_duration (
 151         u32                             start_ticks,
 152         u32                             end_ticks,
 153         u32                             *time_elapsed)
 154 {
 155         acpi_status                     status;
 156         u32                             delta_ticks;
 157         acpi_integer                    quotient;
 158
 159
 160         ACPI_FUNCTION_TRACE ("acpi_get_timer_duration");
 161
 162
 163         if (!time_elapsed) {
 164                 return_ACPI_STATUS (AE_BAD_PARAMETER);
 165         }
 166
 167         /*
 168          * Compute Tick Delta:
 169          * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
 170          */
 171         if (start_ticks < end_ticks) {
 172                 delta_ticks = end_ticks - start_ticks;
 173         }
 174         else if (start_ticks > end_ticks) {
 175                 if (0 == acpi_gbl_FADT->tmr_val_ext) {
 176                         /* 24-bit Timer */
 177
 178                         delta_ticks = (((0x00FFFFFF - start_ticks) + end_ticks) & 0x00FFFFFF);
 179                 }
 180                 else {
 181                         /* 32-bit Timer */
 182
 183                         delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
 184                 }
 185         }
 186         else /* start_ticks == end_ticks */ {
 187                 *time_elapsed = 0;
 188                 return_ACPI_STATUS (AE_OK);
 189         }
 190
 191         /*
 192          * Compute Duration (Requires a 64-bit multiply and divide):
 193          *
 194          * time_elapsed = (delta_ticks * 1000000) / PM_TIMER_FREQUENCY;
 195          */
 196         status = acpi_ut_short_divide (((u64) delta_ticks) * 1000000,
 197                          PM_TIMER_FREQUENCY, &quotient, NULL);
 198
 199         *time_elapsed = (u32) quotient;
 200         return_ACPI_STATUS (status);
 201 }
 202 EXPORT_SYMBOL(acpi_get_timer_duration);
 203