/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
 65acpi_status
 66acpi_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
 99acpi_status
100acpi_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}
117EXPORT_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
149acpi_status
150acpi_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}
202EXPORT_SYMBOL(acpi_get_timer_duration);
203