1 /******************************************************************************
3 * Name: hwtimer.c - ACPI Power Management Timer Interface
5 *****************************************************************************/
8 * Copyright (C) 2000 - 2013, Intel Corp.
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23 * of any contributors may be used to endorse or promote products derived
24 * from this software without specific prior written permission.
26 * Alternatively, this software may be distributed under the terms of the
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44 #include <linux/export.h>
45 #include <acpi/acpi.h>
48 #define _COMPONENT ACPI_HARDWARE
49 ACPI_MODULE_NAME("hwtimer")
51 #if (!ACPI_REDUCED_HARDWARE) /* Entire module */
52 /******************************************************************************
54 * FUNCTION: acpi_get_timer_resolution
56 * PARAMETERS: resolution - Where the resolution is returned
58 * RETURN: Status and timer resolution
60 * DESCRIPTION: Obtains resolution of the ACPI PM Timer (24 or 32 bits).
62 ******************************************************************************/
63 acpi_status acpi_get_timer_resolution(u32 * resolution)
65 ACPI_FUNCTION_TRACE(acpi_get_timer_resolution);
68 return_ACPI_STATUS(AE_BAD_PARAMETER);
71 if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
77 return_ACPI_STATUS(AE_OK);
80 ACPI_EXPORT_SYMBOL(acpi_get_timer_resolution)
82 /******************************************************************************
84 * FUNCTION: acpi_get_timer
86 * PARAMETERS: ticks - Where the timer value is returned
88 * RETURN: Status and current timer value (ticks)
90 * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
92 ******************************************************************************/
93 acpi_status acpi_get_timer(u32 * ticks)
97 ACPI_FUNCTION_TRACE(acpi_get_timer);
100 return_ACPI_STATUS(AE_BAD_PARAMETER);
103 /* ACPI 5.0A: PM Timer is optional */
105 if (!acpi_gbl_FADT.xpm_timer_block.address) {
106 return_ACPI_STATUS(AE_SUPPORT);
109 status = acpi_hw_read(ticks, &acpi_gbl_FADT.xpm_timer_block);
110 return_ACPI_STATUS(status);
113 ACPI_EXPORT_SYMBOL(acpi_get_timer)
115 /******************************************************************************
117 * FUNCTION: acpi_get_timer_duration
119 * PARAMETERS: start_ticks - Starting timestamp
120 * end_ticks - End timestamp
121 * time_elapsed - Where the elapsed time is returned
123 * RETURN: Status and time_elapsed
125 * DESCRIPTION: Computes the time elapsed (in microseconds) between two
126 * PM Timer time stamps, taking into account the possibility of
127 * rollovers, the timer resolution, and timer frequency.
129 * The PM Timer's clock ticks at roughly 3.6 times per
130 * _microsecond_, and its clock continues through Cx state
131 * transitions (unlike many CPU timestamp counters) -- making it
132 * a versatile and accurate timer.
134 * Note that this function accommodates only a single timer
135 * rollover. Thus for 24-bit timers, this function should only
136 * be used for calculating durations less than ~4.6 seconds
137 * (~20 minutes for 32-bit timers) -- calculations below:
139 * 2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
140 * 2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
142 ******************************************************************************/
144 acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 * time_elapsed)
150 ACPI_FUNCTION_TRACE(acpi_get_timer_duration);
153 return_ACPI_STATUS(AE_BAD_PARAMETER);
156 /* ACPI 5.0A: PM Timer is optional */
158 if (!acpi_gbl_FADT.xpm_timer_block.address) {
159 return_ACPI_STATUS(AE_SUPPORT);
163 * Compute Tick Delta:
164 * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
166 if (start_ticks < end_ticks) {
167 delta_ticks = end_ticks - start_ticks;
168 } else if (start_ticks > end_ticks) {
169 if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
174 (((0x00FFFFFF - start_ticks) +
175 end_ticks) & 0x00FFFFFF);
179 delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
181 } else { /* start_ticks == end_ticks */
184 return_ACPI_STATUS(AE_OK);
188 * Compute Duration (Requires a 64-bit multiply and divide):
190 * time_elapsed (microseconds) =
191 * (delta_ticks * ACPI_USEC_PER_SEC) / ACPI_PM_TIMER_FREQUENCY;
193 status = acpi_ut_short_divide(((u64)delta_ticks) * ACPI_USEC_PER_SEC,
194 ACPI_PM_TIMER_FREQUENCY, "ient, NULL);
196 *time_elapsed = (u32) quotient;
197 return_ACPI_STATUS(status);
200 ACPI_EXPORT_SYMBOL(acpi_get_timer_duration)
201 #endif /* !ACPI_REDUCED_HARDWARE */