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hwtimer.c
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1 
2 /******************************************************************************
3  *
4  * Name: hwtimer.c - ACPI Power Management Timer Interface
5  *
6  *****************************************************************************/
7 
8 /*
9  * Copyright (C) 2000 - 2012, Intel Corp.
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/export.h>
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  ******************************************************************************/
65 {
67 
68  if (!resolution) {
70  }
71 
72  if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
73  *resolution = 24;
74  } else {
75  *resolution = 32;
76  }
77 
79 }
80 
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  ******************************************************************************/
95 {
97 
99 
100  if (!ticks) {
102  }
103 
104  status =
105  acpi_hw_read(ticks, &acpi_gbl_FADT.xpm_timer_block);
106 
107  return_ACPI_STATUS(status);
108 }
109 
111 
112 /******************************************************************************
113  *
114  * FUNCTION: acpi_get_timer_duration
115  *
116  * PARAMETERS: start_ticks - Starting timestamp
117  * end_ticks - End timestamp
118  * time_elapsed - Where the elapsed time is returned
119  *
120  * RETURN: Status and time_elapsed
121  *
122  * DESCRIPTION: Computes the time elapsed (in microseconds) between two
123  * PM Timer time stamps, taking into account the possibility of
124  * rollovers, the timer resolution, and timer frequency.
125  *
126  * The PM Timer's clock ticks at roughly 3.6 times per
127  * _microsecond_, and its clock continues through Cx state
128  * transitions (unlike many CPU timestamp counters) -- making it
129  * a versatile and accurate timer.
130  *
131  * Note that this function accommodates only a single timer
132  * rollover. Thus for 24-bit timers, this function should only
133  * be used for calculating durations less than ~4.6 seconds
134  * (~20 minutes for 32-bit timers) -- calculations below:
135  *
136  * 2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
137  * 2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
138  *
139  ******************************************************************************/
141 acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 * time_elapsed)
142 {
144  u32 delta_ticks;
145  u64 quotient;
146 
148 
149  if (!time_elapsed) {
151  }
152 
153  /*
154  * Compute Tick Delta:
155  * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
156  */
157  if (start_ticks < end_ticks) {
158  delta_ticks = end_ticks - start_ticks;
159  } else if (start_ticks > end_ticks) {
160  if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
161 
162  /* 24-bit Timer */
163 
164  delta_ticks =
165  (((0x00FFFFFF - start_ticks) +
166  end_ticks) & 0x00FFFFFF);
167  } else {
168  /* 32-bit Timer */
169 
170  delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
171  }
172  } else { /* start_ticks == end_ticks */
173 
174  *time_elapsed = 0;
176  }
177 
178  /*
179  * Compute Duration (Requires a 64-bit multiply and divide):
180  *
181  * time_elapsed = (delta_ticks * 1000000) / PM_TIMER_FREQUENCY;
182  */
183  status = acpi_ut_short_divide(((u64) delta_ticks) * 1000000,
184  PM_TIMER_FREQUENCY, &quotient, NULL);
185 
186  *time_elapsed = (u32) quotient;
187  return_ACPI_STATUS(status);
188 }
189 
191 #endif /* !ACPI_REDUCED_HARDWARE */