2 /******************************************************************************
4 * Name: hwtimer.c - ACPI Power Management Timer Interface
6 *****************************************************************************/
9 * Copyright (C) 2000 - 2005, R. Byron Moore
10 * All rights reserved.
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
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.
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.
32 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
33 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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45 #include <linux/module.h>
46 #include <acpi/acpi.h>
48 #define _COMPONENT ACPI_HARDWARE
49 ACPI_MODULE_NAME ("hwtimer")
52 /******************************************************************************
54 * FUNCTION: acpi_get_timer_resolution
56 * PARAMETERS: Resolution - Where the resolution is returned
58 * RETURN: Status and timer resolution
60 * DESCRIPTION: Obtains resolution of the ACPI PM Timer (24 or 32 bits).
62 ******************************************************************************/
65 acpi_get_timer_resolution (
68 ACPI_FUNCTION_TRACE ("acpi_get_timer_resolution");
72 return_ACPI_STATUS (AE_BAD_PARAMETER);
75 if (0 == acpi_gbl_FADT->tmr_val_ext) {
82 return_ACPI_STATUS (AE_OK);
86 /******************************************************************************
88 * FUNCTION: acpi_get_timer
90 * PARAMETERS: Ticks - Where the timer value is returned
92 * RETURN: Status and current timer value (ticks)
94 * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
96 ******************************************************************************/
105 ACPI_FUNCTION_TRACE ("acpi_get_timer");
109 return_ACPI_STATUS (AE_BAD_PARAMETER);
112 status = acpi_hw_low_level_read (32, ticks, &acpi_gbl_FADT->xpm_tmr_blk);
114 return_ACPI_STATUS (status);
116 EXPORT_SYMBOL(acpi_get_timer);
119 /******************************************************************************
121 * FUNCTION: acpi_get_timer_duration
123 * PARAMETERS: start_ticks - Starting timestamp
124 * end_ticks - End timestamp
125 * time_elapsed - Where the elapsed time is returned
127 * RETURN: Status and time_elapsed
129 * DESCRIPTION: Computes the time elapsed (in microseconds) between two
130 * PM Timer time stamps, taking into account the possibility of
131 * rollovers, the timer resolution, and timer frequency.
133 * The PM Timer's clock ticks at roughly 3.6 times per
134 * _microsecond_, and its clock continues through Cx state
135 * transitions (unlike many CPU timestamp counters) -- making it
136 * a versatile and accurate timer.
138 * Note that this function accommodates only a single timer
139 * rollover. Thus for 24-bit timers, this function should only
140 * be used for calculating durations less than ~4.6 seconds
141 * (~20 minutes for 32-bit timers) -- calculations below:
143 * 2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
144 * 2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
146 ******************************************************************************/
149 acpi_get_timer_duration (
156 acpi_integer quotient;
159 ACPI_FUNCTION_TRACE ("acpi_get_timer_duration");
163 return_ACPI_STATUS (AE_BAD_PARAMETER);
167 * Compute Tick Delta:
168 * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
170 if (start_ticks < end_ticks) {
171 delta_ticks = end_ticks - start_ticks;
173 else if (start_ticks > end_ticks) {
174 if (0 == acpi_gbl_FADT->tmr_val_ext) {
177 delta_ticks = (((0x00FFFFFF - start_ticks) + end_ticks) & 0x00FFFFFF);
182 delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
185 else /* start_ticks == end_ticks */ {
187 return_ACPI_STATUS (AE_OK);
191 * Compute Duration (Requires a 64-bit multiply and divide):
193 * time_elapsed = (delta_ticks * 1000000) / PM_TIMER_FREQUENCY;
195 status = acpi_ut_short_divide (((u64) delta_ticks) * 1000000,
196 PM_TIMER_FREQUENCY, "ient, NULL);
198 *time_elapsed = (u32) quotient;
199 return_ACPI_STATUS (status);
202 EXPORT_SYMBOL(acpi_get_timer_duration);