2 /******************************************************************************
4 * Name: hwtimer.c - ACPI Power Management Timer Interface
6 *****************************************************************************/
9 * Copyright (C) 2000 - 2006, 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
34 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
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36 * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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42 * POSSIBILITY OF SUCH DAMAGES.
45 #include <acpi/acpi.h>
47 #define _COMPONENT ACPI_HARDWARE
48 ACPI_MODULE_NAME("hwtimer")
50 /******************************************************************************
52 * FUNCTION: acpi_get_timer_resolution
54 * PARAMETERS: Resolution - Where the resolution is returned
56 * RETURN: Status and timer resolution
58 * DESCRIPTION: Obtains resolution of the ACPI PM Timer (24 or 32 bits).
60 ******************************************************************************/
61 acpi_status
acpi_get_timer_resolution(u32
* resolution
)
63 ACPI_FUNCTION_TRACE(acpi_get_timer_resolution
);
66 return_ACPI_STATUS(AE_BAD_PARAMETER
);
69 if (acpi_gbl_FADT
->tmr_val_ext
== 0) {
75 return_ACPI_STATUS(AE_OK
);
78 ACPI_EXPORT_SYMBOL(acpi_get_timer_resolution
)
80 /******************************************************************************
82 * FUNCTION: acpi_get_timer
84 * PARAMETERS: Ticks - Where the timer value is returned
86 * RETURN: Status and current timer value (ticks)
88 * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
90 ******************************************************************************/
91 acpi_status
acpi_get_timer(u32
* ticks
)
95 ACPI_FUNCTION_TRACE(acpi_get_timer
);
98 return_ACPI_STATUS(AE_BAD_PARAMETER
);
101 status
= acpi_hw_low_level_read(32, ticks
, &acpi_gbl_FADT
->xpm_tmr_blk
);
103 return_ACPI_STATUS(status
);
106 ACPI_EXPORT_SYMBOL(acpi_get_timer
)
108 /******************************************************************************
110 * FUNCTION: acpi_get_timer_duration
112 * PARAMETERS: start_ticks - Starting timestamp
113 * end_ticks - End timestamp
114 * time_elapsed - Where the elapsed time is returned
116 * RETURN: Status and time_elapsed
118 * DESCRIPTION: Computes the time elapsed (in microseconds) between two
119 * PM Timer time stamps, taking into account the possibility of
120 * rollovers, the timer resolution, and timer frequency.
122 * The PM Timer's clock ticks at roughly 3.6 times per
123 * _microsecond_, and its clock continues through Cx state
124 * transitions (unlike many CPU timestamp counters) -- making it
125 * a versatile and accurate timer.
127 * Note that this function accommodates only a single timer
128 * rollover. Thus for 24-bit timers, this function should only
129 * be used for calculating durations less than ~4.6 seconds
130 * (~20 minutes for 32-bit timers) -- calculations below:
132 * 2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
133 * 2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
135 ******************************************************************************/
137 acpi_get_timer_duration(u32 start_ticks
, u32 end_ticks
, u32
* time_elapsed
)
141 acpi_integer quotient
;
143 ACPI_FUNCTION_TRACE(acpi_get_timer_duration
);
146 return_ACPI_STATUS(AE_BAD_PARAMETER
);
150 * Compute Tick Delta:
151 * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
153 if (start_ticks
< end_ticks
) {
154 delta_ticks
= end_ticks
- start_ticks
;
155 } else if (start_ticks
> end_ticks
) {
156 if (acpi_gbl_FADT
->tmr_val_ext
== 0) {
161 (((0x00FFFFFF - start_ticks
) +
162 end_ticks
) & 0x00FFFFFF);
166 delta_ticks
= (0xFFFFFFFF - start_ticks
) + end_ticks
;
168 } else { /* start_ticks == end_ticks */
171 return_ACPI_STATUS(AE_OK
);
175 * Compute Duration (Requires a 64-bit multiply and divide):
177 * time_elapsed = (delta_ticks * 1000000) / PM_TIMER_FREQUENCY;
179 status
= acpi_ut_short_divide(((u64
) delta_ticks
) * 1000000,
180 PM_TIMER_FREQUENCY
, "ient
, NULL
);
182 *time_elapsed
= (u32
) quotient
;
183 return_ACPI_STATUS(status
);
186 ACPI_EXPORT_SYMBOL(acpi_get_timer_duration
)