drivers/acpi/acpica/hwtimer.c

   1
   2 /******************************************************************************
   3  *
   4  * Name: hwtimer.c - ACPI Power Management Timer Interface
   5  *
   6  *****************************************************************************/
   7
   8 /*
   9  * Copyright (C) 2000 - 2011, Intel Corp.
  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/export.h>
  46 #include <acpi/acpi.h>
  47 #include "accommon.h"
  48
  49 #define _COMPONENT          ACPI_HARDWARE
  50 ACPI_MODULE_NAME("hwtimer")
  51
  52 /******************************************************************************
  53  *
  54  * FUNCTION:    acpi_get_timer_resolution
  55  *
  56  * PARAMETERS:  Resolution          - Where the resolution is returned
  57  *
  58  * RETURN:      Status and timer resolution
  59  *
  60  * DESCRIPTION: Obtains resolution of the ACPI PM Timer (24 or 32 bits).
  61  *
  62  ******************************************************************************/
  63 acpi_status acpi_get_timer_resolution(u32 * resolution)
  64 {
  65         ACPI_FUNCTION_TRACE(acpi_get_timer_resolution);
  66
  67         if (!resolution) {
  68                 return_ACPI_STATUS(AE_BAD_PARAMETER);
  69         }
  70
  71         if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
  72                 *resolution = 24;
  73         } else {
  74                 *resolution = 32;
  75         }
  76
  77         return_ACPI_STATUS(AE_OK);
  78 }
  79
  80 ACPI_EXPORT_SYMBOL(acpi_get_timer_resolution)
  81
  82 /******************************************************************************
  83  *
  84  * FUNCTION:    acpi_get_timer
  85  *
  86  * PARAMETERS:  Ticks               - Where the timer value is returned
  87  *
  88  * RETURN:      Status and current timer value (ticks)
  89  *
  90  * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
  91  *
  92  ******************************************************************************/
  93 acpi_status acpi_get_timer(u32 * ticks)
  94 {
  95         acpi_status status;
  96
  97         ACPI_FUNCTION_TRACE(acpi_get_timer);
  98
  99         if (!ticks) {
 100                 return_ACPI_STATUS(AE_BAD_PARAMETER);
 101         }
 102
 103         status =
 104             acpi_hw_read(ticks, &acpi_gbl_FADT.xpm_timer_block);
 105
 106         return_ACPI_STATUS(status);
 107 }
 108
 109 ACPI_EXPORT_SYMBOL(acpi_get_timer)
 110
 111 /******************************************************************************
 112  *
 113  * FUNCTION:    acpi_get_timer_duration
 114  *
 115  * PARAMETERS:  start_ticks         - Starting timestamp
 116  *              end_ticks           - End timestamp
 117  *              time_elapsed        - Where the elapsed time is returned
 118  *
 119  * RETURN:      Status and time_elapsed
 120  *
 121  * DESCRIPTION: Computes the time elapsed (in microseconds) between two
 122  *              PM Timer time stamps, taking into account the possibility of
 123  *              rollovers, the timer resolution, and timer frequency.
 124  *
 125  *              The PM Timer's clock ticks at roughly 3.6 times per
 126  *              _microsecond_, and its clock continues through Cx state
 127  *              transitions (unlike many CPU timestamp counters) -- making it
 128  *              a versatile and accurate timer.
 129  *
 130  *              Note that this function accommodates only a single timer
 131  *              rollover.  Thus for 24-bit timers, this function should only
 132  *              be used for calculating durations less than ~4.6 seconds
 133  *              (~20 minutes for 32-bit timers) -- calculations below:
 134  *
 135  *              2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
 136  *              2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
 137  *
 138  ******************************************************************************/
 139 acpi_status
 140 acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 * time_elapsed)
 141 {
 142         acpi_status status;
 143         u32 delta_ticks;
 144         u64 quotient;
 145
 146         ACPI_FUNCTION_TRACE(acpi_get_timer_duration);
 147
 148         if (!time_elapsed) {
 149                 return_ACPI_STATUS(AE_BAD_PARAMETER);
 150         }
 151
 152         /*
 153          * Compute Tick Delta:
 154          * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
 155          */
 156         if (start_ticks < end_ticks) {
 157                 delta_ticks = end_ticks - start_ticks;
 158         } else if (start_ticks > end_ticks) {
 159                 if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
 160
 161                         /* 24-bit Timer */
 162
 163                         delta_ticks =
 164                             (((0x00FFFFFF - start_ticks) +
 165                               end_ticks) & 0x00FFFFFF);
 166                 } else {
 167                         /* 32-bit Timer */
 168
 169                         delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
 170                 }
 171         } else {                /* start_ticks == end_ticks */
 172
 173                 *time_elapsed = 0;
 174                 return_ACPI_STATUS(AE_OK);
 175         }
 176
 177         /*
 178          * Compute Duration (Requires a 64-bit multiply and divide):
 179          *
 180          * time_elapsed = (delta_ticks * 1000000) / PM_TIMER_FREQUENCY;
 181          */
 182         status = acpi_ut_short_divide(((u64) delta_ticks) * 1000000,
 183                                       PM_TIMER_FREQUENCY, &quotient, NULL);
 184
 185         *time_elapsed = (u32) quotient;
 186         return_ACPI_STATUS(status);
 187 }
 188
 189 ACPI_EXPORT_SYMBOL(acpi_get_timer_duration)