2 /******************************************************************************
4 * Name: hwtimer.c - ACPI Power Management Timer Interface
6 *****************************************************************************/
9 * Copyright (C) 2000 - 2012, Intel Corp.
10 * All rights reserved.
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13 * modification, are permitted provided that the following conditions
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17 * without modification.
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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.
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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.
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45 #include <linux/export.h>
46 #include <acpi/acpi.h>
49 #define _COMPONENT ACPI_HARDWARE
50 ACPI_MODULE_NAME("hwtimer")
52 #if (!ACPI_REDUCED_HARDWARE) /* Entire module */
53 /******************************************************************************
55 * FUNCTION: acpi_get_timer_resolution
57 * PARAMETERS: resolution - Where the resolution is returned
59 * RETURN: Status and timer resolution
61 * DESCRIPTION: Obtains resolution of the ACPI PM Timer (24 or 32 bits).
63 ******************************************************************************/
64 acpi_status
acpi_get_timer_resolution(u32
* resolution
)
66 ACPI_FUNCTION_TRACE(acpi_get_timer_resolution
);
69 return_ACPI_STATUS(AE_BAD_PARAMETER
);
72 if ((acpi_gbl_FADT
.flags
& ACPI_FADT_32BIT_TIMER
) == 0) {
78 return_ACPI_STATUS(AE_OK
);
81 ACPI_EXPORT_SYMBOL(acpi_get_timer_resolution
)
83 /******************************************************************************
85 * FUNCTION: acpi_get_timer
87 * PARAMETERS: ticks - Where the timer value is returned
89 * RETURN: Status and current timer value (ticks)
91 * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
93 ******************************************************************************/
94 acpi_status
acpi_get_timer(u32
* ticks
)
98 ACPI_FUNCTION_TRACE(acpi_get_timer
);
101 return_ACPI_STATUS(AE_BAD_PARAMETER
);
105 acpi_hw_read(ticks
, &acpi_gbl_FADT
.xpm_timer_block
);
107 return_ACPI_STATUS(status
);
110 ACPI_EXPORT_SYMBOL(acpi_get_timer
)
112 /******************************************************************************
114 * FUNCTION: acpi_get_timer_duration
116 * PARAMETERS: start_ticks - Starting timestamp
117 * end_ticks - End timestamp
118 * time_elapsed - Where the elapsed time is returned
120 * RETURN: Status and time_elapsed
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.
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.
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:
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
139 ******************************************************************************/
141 acpi_get_timer_duration(u32 start_ticks
, u32 end_ticks
, u32
* time_elapsed
)
147 ACPI_FUNCTION_TRACE(acpi_get_timer_duration
);
150 return_ACPI_STATUS(AE_BAD_PARAMETER
);
154 * Compute Tick Delta:
155 * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
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) {
165 (((0x00FFFFFF - start_ticks
) +
166 end_ticks
) & 0x00FFFFFF);
170 delta_ticks
= (0xFFFFFFFF - start_ticks
) + end_ticks
;
172 } else { /* start_ticks == end_ticks */
175 return_ACPI_STATUS(AE_OK
);
179 * Compute Duration (Requires a 64-bit multiply and divide):
181 * time_elapsed = (delta_ticks * 1000000) / PM_TIMER_FREQUENCY;
183 status
= acpi_ut_short_divide(((u64
) delta_ticks
) * 1000000,
184 PM_TIMER_FREQUENCY
, "ient
, NULL
);
186 *time_elapsed
= (u32
) quotient
;
187 return_ACPI_STATUS(status
);
190 ACPI_EXPORT_SYMBOL(acpi_get_timer_duration
)
191 #endif /* !ACPI_REDUCED_HARDWARE */