reactos/drivers/bus/acpi/hardware/hwtimer.c

   1
   2 /******************************************************************************
   3  *
   4  * Name: hwtimer.c - ACPI Power Management Timer Interface
   5  *              $Revision: 1.1 $
   6  *
   7  *****************************************************************************/
   8
   9 /*
  10  *  Copyright (C) 2000, 2001 R. Byron Moore
  11  *
  12  *  This program is free software; you can redistribute it and/or modify
  13  *  it under the terms of the GNU General Public License as published by
  14  *  the Free Software Foundation; either version 2 of the License, or
  15  *  (at your option) any later version.
  16  *
  17  *  This program is distributed in the hope that it will be useful,
  18  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  *  GNU General Public License for more details.
  21  *
  22  *  You should have received a copy of the GNU General Public License
  23  *  along with this program; if not, write to the Free Software
  24  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  25  */
  26
  27 #include "acpi.h"
  28 #include "achware.h"
  29
  30 #define _COMPONENT          ACPI_HARDWARE
  31          MODULE_NAME         ("hwtimer")
  32
  33
  34 /******************************************************************************
  35  *
  36  * FUNCTION:    Acpi_get_timer_resolution
  37  *
  38  * PARAMETERS:  none
  39  *
  40  * RETURN:      Number of bits of resolution in the PM Timer (24 or 32).
  41  *
  42  * DESCRIPTION: Obtains resolution of the ACPI PM Timer.
  43  *
  44  ******************************************************************************/
  45
  46 ACPI_STATUS
  47 acpi_get_timer_resolution (
  48         u32                     *resolution)
  49 {
  50         if (!resolution) {
  51                 return (AE_BAD_PARAMETER);
  52         }
  53
  54         if (0 == acpi_gbl_FADT->tmr_val_ext) {
  55                 *resolution = 24;
  56         }
  57         else {
  58                 *resolution = 32;
  59         }
  60
  61         return (AE_OK);
  62 }
  63
  64
  65 /******************************************************************************
  66  *
  67  * FUNCTION:    Acpi_get_timer
  68  *
  69  * PARAMETERS:  none
  70  *
  71  * RETURN:      Current value of the ACPI PM Timer (in ticks).
  72  *
  73  * DESCRIPTION: Obtains current value of ACPI PM Timer.
  74  *
  75  ******************************************************************************/
  76
  77 ACPI_STATUS
  78 acpi_get_timer (
  79         u32                     *ticks)
  80 {
  81         if (!ticks) {
  82                 return (AE_BAD_PARAMETER);
  83         }
  84
  85         *ticks = acpi_os_in32 ((ACPI_IO_ADDRESS) ACPI_GET_ADDRESS (acpi_gbl_FADT->Xpm_tmr_blk.address));
  86
  87         return (AE_OK);
  88 }
  89
  90
  91 /******************************************************************************
  92  *
  93  * FUNCTION:    Acpi_get_timer_duration
  94  *
  95  * PARAMETERS:  Start_ticks
  96  *              End_ticks
  97  *              Time_elapsed
  98  *
  99  * RETURN:      Time_elapsed
 100  *
 101  * DESCRIPTION: Computes the time elapsed (in microseconds) between two
 102  *              PM Timer time stamps, taking into account the possibility of
 103  *              rollovers, the timer resolution, and timer frequency.
 104  *
 105  *              The PM Timer's clock ticks at roughly 3.6 times per
 106  *              _microsecond_, and its clock continues through Cx state
 107  *              transitions (unlike many CPU timestamp counters) -- making it
 108  *              a versatile and accurate timer.
 109  *
 110  *              Note that this function accomodates only a single timer
 111  *              rollover.  Thus for 24-bit timers, this function should only
 112  *              be used for calculating durations less than ~4.6 seconds
 113  *              (~20 hours for 32-bit timers).
 114  *
 115  ******************************************************************************/
 116
 117 ACPI_STATUS
 118 acpi_get_timer_duration (
 119         u32                     start_ticks,
 120         u32                     end_ticks,
 121         u32                     *time_elapsed)
 122 {
 123         u32                     delta_ticks = 0;
 124         u32                     seconds = 0;
 125         u32                     milliseconds = 0;
 126         u32                     microseconds = 0;
 127         u32                     remainder = 0;
 128
 129         if (!time_elapsed) {
 130                 return (AE_BAD_PARAMETER);
 131         }
 132
 133         /*
 134          * Compute Tick Delta:
 135          * -------------------
 136          * Handle (max one) timer rollovers on 24- versus 32-bit timers.
 137          */
 138         if (start_ticks < end_ticks) {
 139                 delta_ticks = end_ticks - start_ticks;
 140         }
 141         else if (start_ticks > end_ticks) {
 142                 /* 24-bit Timer */
 143                 if (0 == acpi_gbl_FADT->tmr_val_ext) {
 144                         delta_ticks = (((0x00FFFFFF - start_ticks) + end_ticks) & 0x00FFFFFF);
 145                 }
 146                 /* 32-bit Timer */
 147                 else {
 148                         delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
 149                 }
 150         }
 151         else {
 152                 *time_elapsed = 0;
 153                 return (AE_OK);
 154         }
 155
 156         /*
 157          * Compute Duration:
 158          * -----------------
 159          * Since certain compilers (gcc/Linux, argh!) don't support 64-bit
 160          * divides in kernel-space we have to do some trickery to preserve
 161          * accuracy while using 32-bit math.
 162          *
 163          * TODO: Change to use 64-bit math when supported.
 164          *
 165          * The process is as follows:
 166          *  1. Compute the number of seconds by dividing Delta Ticks by
 167          *     the timer frequency.
 168          *  2. Compute the number of milliseconds in the remainder from step #1
 169          *     by multiplying by 1000 and then dividing by the timer frequency.
 170          *  3. Compute the number of microseconds in the remainder from step #2
 171          *     by multiplying by 1000 and then dividing by the timer frequency.
 172          *  4. Add the results from steps 1, 2, and 3 to get the total duration.
 173          *
 174          * Example: The time elapsed for Delta_ticks = 0xFFFFFFFF should be
 175          *          1199864031 microseconds.  This is computed as follows:
 176          *          Step #1: Seconds = 1199; Remainder = 3092840
 177          *          Step #2: Milliseconds = 864; Remainder = 113120
 178          *          Step #3: Microseconds = 31; Remainder = <don't care!>
 179          */
 180
 181         /* Step #1 */
 182         seconds = delta_ticks / PM_TIMER_FREQUENCY;
 183         remainder = delta_ticks % PM_TIMER_FREQUENCY;
 184
 185         /* Step #2 */
 186         milliseconds = (remainder * 1000) / PM_TIMER_FREQUENCY;
 187         remainder = (remainder * 1000) % PM_TIMER_FREQUENCY;
 188
 189         /* Step #3 */
 190         microseconds = (remainder * 1000) / PM_TIMER_FREQUENCY;
 191
 192         /* Step #4 */
 193         *time_elapsed = seconds * 1000000;
 194         *time_elapsed += milliseconds * 1000;
 195         *time_elapsed += microseconds;
 196
 197         return (AE_OK);
 198 }
 199
 200