git.oblomov.eu Git - linux-2.6/blob - 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 <acpi/acpi.h>
  46
  47 #define _COMPONENT          ACPI_HARDWARE
  48 ACPI_MODULE_NAME("hwtimer")
  49
  50 /******************************************************************************
  51  *
  52  * FUNCTION:    acpi_get_timer_resolution
  53  *
  54  * PARAMETERS:  Resolution          - Where the resolution is returned
  55  *
  56  * RETURN:      Status and timer resolution
  57  *
  58  * DESCRIPTION: Obtains resolution of the ACPI PM Timer (24 or 32 bits).
  59  *
  60  ******************************************************************************/
  61 acpi_status acpi_get_timer_resolution(u32 * resolution)
  62 {
  63         ACPI_FUNCTION_TRACE(acpi_get_timer_resolution);
  64
  65         if (!resolution) {
  66                 return_ACPI_STATUS(AE_BAD_PARAMETER);
  67         }
  68
  69         if (acpi_gbl_FADT->tmr_val_ext == 0) {
  70                 *resolution = 24;
  71         } else {
  72                 *resolution = 32;
  73         }
  74
  75         return_ACPI_STATUS(AE_OK);
  76 }
  77
  78 ACPI_EXPORT_SYMBOL(acpi_get_timer_resolution)
  79
  80 /******************************************************************************
  81  *
  82  * FUNCTION:    acpi_get_timer
  83  *
  84  * PARAMETERS:  Ticks               - Where the timer value is returned
  85  *
  86  * RETURN:      Status and current timer value (ticks)
  87  *
  88  * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
  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 ACPI_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 acpi_status
 137 acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 * time_elapsed)
 138 {
 139         acpi_status status;
 140         u32 delta_ticks;
 141         acpi_integer quotient;
 142
 143         ACPI_FUNCTION_TRACE(acpi_get_timer_duration);
 144
 145         if (!time_elapsed) {
 146                 return_ACPI_STATUS(AE_BAD_PARAMETER);
 147         }
 148
 149         /*
 150          * Compute Tick Delta:
 151          * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
 152          */
 153         if (start_ticks < end_ticks) {
 154                 delta_ticks = end_ticks - start_ticks;
 155         } else if (start_ticks > end_ticks) {
 156                 if (acpi_gbl_FADT->tmr_val_ext == 0) {
 157
 158                         /* 24-bit Timer */
 159
 160                         delta_ticks =
 161                             (((0x00FFFFFF - start_ticks) +
 162                               end_ticks) & 0x00FFFFFF);
 163                 } else {
 164                         /* 32-bit Timer */
 165
 166                         delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
 167                 }
 168         } else {                /* start_ticks == end_ticks */
 169
 170                 *time_elapsed = 0;
 171                 return_ACPI_STATUS(AE_OK);
 172         }
 173
 174         /*
 175          * Compute Duration (Requires a 64-bit multiply and divide):
 176          *
 177          * time_elapsed = (delta_ticks * 1000000) / PM_TIMER_FREQUENCY;
 178          */
 179         status = acpi_ut_short_divide(((u64) delta_ticks) * 1000000,
 180                                       PM_TIMER_FREQUENCY, &quotient, NULL);
 181
 182         *time_elapsed = (u32) quotient;
 183         return_ACPI_STATUS(status);
 184 }
 185
 186 ACPI_EXPORT_SYMBOL(acpi_get_timer_duration)