2 /******************************************************************************
4 * Name: hwtimer.c - ACPI Power Management Timer Interface
6 *****************************************************************************/
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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.
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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);
104 status = acpi_hw_read(ticks, &acpi_gbl_FADT.xpm_timer_block);
106 return_ACPI_STATUS(status);
109 ACPI_EXPORT_SYMBOL(acpi_get_timer)
111 /******************************************************************************
113 * FUNCTION: acpi_get_timer_duration
115 * PARAMETERS: start_ticks - Starting timestamp
116 * end_ticks - End timestamp
117 * time_elapsed - Where the elapsed time is returned
119 * RETURN: Status and time_elapsed
121 * DESCRIPTION: Computes the time elapsed (in microseconds) between two
122 * PM Timer time stamps, taking into account the possibility of
123 * rollovers, the timer resolution, and timer frequency.
125 * The PM Timer's clock ticks at roughly 3.6 times per
126 * _microsecond_, and its clock continues through Cx state
127 * transitions (unlike many CPU timestamp counters) -- making it
128 * a versatile and accurate timer.
130 * Note that this function accommodates only a single timer
131 * rollover. Thus for 24-bit timers, this function should only
132 * be used for calculating durations less than ~4.6 seconds
133 * (~20 minutes for 32-bit timers) -- calculations below:
135 * 2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
136 * 2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
138 ******************************************************************************/
140 acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 * time_elapsed)
146 ACPI_FUNCTION_TRACE(acpi_get_timer_duration);
149 return_ACPI_STATUS(AE_BAD_PARAMETER);
153 * Compute Tick Delta:
154 * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
156 if (start_ticks < end_ticks) {
157 delta_ticks = end_ticks - start_ticks;
158 } else if (start_ticks > end_ticks) {
159 if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
164 (((0x00FFFFFF - start_ticks) +
165 end_ticks) & 0x00FFFFFF);
169 delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
171 } else { /* start_ticks == end_ticks */
174 return_ACPI_STATUS(AE_OK);
178 * Compute Duration (Requires a 64-bit multiply and divide):
180 * time_elapsed = (delta_ticks * 1000000) / PM_TIMER_FREQUENCY;
182 status = acpi_ut_short_divide(((u64) delta_ticks) * 1000000,
183 PM_TIMER_FREQUENCY, "ient, NULL);
185 *time_elapsed = (u32) quotient;
186 return_ACPI_STATUS(status);
189 ACPI_EXPORT_SYMBOL(acpi_get_timer_duration)
190 #endif /* !ACPI_REDUCED_HARDWARE */