xref: /openbmc/linux/drivers/acpi/acpica/hwtimer.c (revision c819e2cf)
1 /******************************************************************************
2  *
3  * Name: hwtimer.c - ACPI Power Management Timer Interface
4  *
5  *****************************************************************************/
6 
7 /*
8  * Copyright (C) 2000 - 2014, Intel Corp.
9  * All rights reserved.
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions
13  * are met:
14  * 1. Redistributions of source code must retain the above copyright
15  *    notice, this list of conditions, and the following disclaimer,
16  *    without modification.
17  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
18  *    substantially similar to the "NO WARRANTY" disclaimer below
19  *    ("Disclaimer") and any redistribution must be conditioned upon
20  *    including a substantially similar Disclaimer requirement for further
21  *    binary redistribution.
22  * 3. Neither the names of the above-listed copyright holders nor the names
23  *    of any contributors may be used to endorse or promote products derived
24  *    from this software without specific prior written permission.
25  *
26  * Alternatively, this software may be distributed under the terms of the
27  * GNU General Public License ("GPL") version 2 as published by the Free
28  * Software Foundation.
29  *
30  * NO WARRANTY
31  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
32  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
33  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
34  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
35  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
36  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
37  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
40  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
41  * POSSIBILITY OF SUCH DAMAGES.
42  */
43 
44 #define EXPORT_ACPI_INTERFACES
45 
46 #include <acpi/acpi.h>
47 #include "accommon.h"
48 
49 #define _COMPONENT          ACPI_HARDWARE
50 ACPI_MODULE_NAME("hwtimer")
51 
52 #if (!ACPI_REDUCED_HARDWARE)	/* Entire module */
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 acpi_status acpi_get_timer_resolution(u32 * resolution)
65 {
66 	ACPI_FUNCTION_TRACE(acpi_get_timer_resolution);
67 
68 	if (!resolution) {
69 		return_ACPI_STATUS(AE_BAD_PARAMETER);
70 	}
71 
72 	if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
73 		*resolution = 24;
74 	} else {
75 		*resolution = 32;
76 	}
77 
78 	return_ACPI_STATUS(AE_OK);
79 }
80 
81 ACPI_EXPORT_SYMBOL(acpi_get_timer_resolution)
82 
83 /******************************************************************************
84  *
85  * FUNCTION:    acpi_get_timer
86  *
87  * PARAMETERS:  ticks               - Where the timer value is returned
88  *
89  * RETURN:      Status and current timer value (ticks)
90  *
91  * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
92  *
93  ******************************************************************************/
94 acpi_status acpi_get_timer(u32 * ticks)
95 {
96 	acpi_status status;
97 
98 	ACPI_FUNCTION_TRACE(acpi_get_timer);
99 
100 	if (!ticks) {
101 		return_ACPI_STATUS(AE_BAD_PARAMETER);
102 	}
103 
104 	/* ACPI 5.0A: PM Timer is optional */
105 
106 	if (!acpi_gbl_FADT.xpm_timer_block.address) {
107 		return_ACPI_STATUS(AE_SUPPORT);
108 	}
109 
110 	status = acpi_hw_read(ticks, &acpi_gbl_FADT.xpm_timer_block);
111 	return_ACPI_STATUS(status);
112 }
113 
114 ACPI_EXPORT_SYMBOL(acpi_get_timer)
115 
116 /******************************************************************************
117  *
118  * FUNCTION:    acpi_get_timer_duration
119  *
120  * PARAMETERS:  start_ticks         - Starting timestamp
121  *              end_ticks           - End timestamp
122  *              time_elapsed        - Where the elapsed time is returned
123  *
124  * RETURN:      Status and time_elapsed
125  *
126  * DESCRIPTION: Computes the time elapsed (in microseconds) between two
127  *              PM Timer time stamps, taking into account the possibility of
128  *              rollovers, the timer resolution, and timer frequency.
129  *
130  *              The PM Timer's clock ticks at roughly 3.6 times per
131  *              _microsecond_, and its clock continues through Cx state
132  *              transitions (unlike many CPU timestamp counters) -- making it
133  *              a versatile and accurate timer.
134  *
135  *              Note that this function accommodates only a single timer
136  *              rollover. Thus for 24-bit timers, this function should only
137  *              be used for calculating durations less than ~4.6 seconds
138  *              (~20 minutes for 32-bit timers) -- calculations below:
139  *
140  *              2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
141  *              2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
142  *
143  ******************************************************************************/
144 acpi_status
145 acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 * time_elapsed)
146 {
147 	acpi_status status;
148 	u32 delta_ticks;
149 	u64 quotient;
150 
151 	ACPI_FUNCTION_TRACE(acpi_get_timer_duration);
152 
153 	if (!time_elapsed) {
154 		return_ACPI_STATUS(AE_BAD_PARAMETER);
155 	}
156 
157 	/* ACPI 5.0A: PM Timer is optional */
158 
159 	if (!acpi_gbl_FADT.xpm_timer_block.address) {
160 		return_ACPI_STATUS(AE_SUPPORT);
161 	}
162 
163 	/*
164 	 * Compute Tick Delta:
165 	 * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
166 	 */
167 	if (start_ticks < end_ticks) {
168 		delta_ticks = end_ticks - start_ticks;
169 	} else if (start_ticks > end_ticks) {
170 		if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
171 
172 			/* 24-bit Timer */
173 
174 			delta_ticks =
175 			    (((0x00FFFFFF - start_ticks) +
176 			      end_ticks) & 0x00FFFFFF);
177 		} else {
178 			/* 32-bit Timer */
179 
180 			delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
181 		}
182 	} else {		/* start_ticks == end_ticks */
183 
184 		*time_elapsed = 0;
185 		return_ACPI_STATUS(AE_OK);
186 	}
187 
188 	/*
189 	 * Compute Duration (Requires a 64-bit multiply and divide):
190 	 *
191 	 * time_elapsed (microseconds) =
192 	 *  (delta_ticks * ACPI_USEC_PER_SEC) / ACPI_PM_TIMER_FREQUENCY;
193 	 */
194 	status = acpi_ut_short_divide(((u64)delta_ticks) * ACPI_USEC_PER_SEC,
195 				      ACPI_PM_TIMER_FREQUENCY, &quotient, NULL);
196 
197 	*time_elapsed = (u32) quotient;
198 	return_ACPI_STATUS(status);
199 }
200 
201 ACPI_EXPORT_SYMBOL(acpi_get_timer_duration)
202 #endif				/* !ACPI_REDUCED_HARDWARE */
203