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/drivers/acpi/acpica/hwtimer.c

http://github.com/mirrors/linux
C | 175 lines | 71 code | 31 blank | 73 comment | 15 complexity | fcf46b5c9db7205d5dd2749cf3415251 MD5 | raw file
  1// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
  2/******************************************************************************
  3 *
  4 * Name: hwtimer.c - ACPI Power Management Timer Interface
  5 *
  6 * Copyright (C) 2000 - 2020, Intel Corp.
  7 *
  8 *****************************************************************************/
  9
 10#define EXPORT_ACPI_INTERFACES
 11
 12#include <acpi/acpi.h>
 13#include "accommon.h"
 14
 15#define _COMPONENT          ACPI_HARDWARE
 16ACPI_MODULE_NAME("hwtimer")
 17
 18#if (!ACPI_REDUCED_HARDWARE)	/* Entire module */
 19/******************************************************************************
 20 *
 21 * FUNCTION:    acpi_get_timer_resolution
 22 *
 23 * PARAMETERS:  resolution          - Where the resolution is returned
 24 *
 25 * RETURN:      Status and timer resolution
 26 *
 27 * DESCRIPTION: Obtains resolution of the ACPI PM Timer (24 or 32 bits).
 28 *
 29 ******************************************************************************/
 30acpi_status acpi_get_timer_resolution(u32 * resolution)
 31{
 32	ACPI_FUNCTION_TRACE(acpi_get_timer_resolution);
 33
 34	if (!resolution) {
 35		return_ACPI_STATUS(AE_BAD_PARAMETER);
 36	}
 37
 38	if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
 39		*resolution = 24;
 40	} else {
 41		*resolution = 32;
 42	}
 43
 44	return_ACPI_STATUS(AE_OK);
 45}
 46
 47ACPI_EXPORT_SYMBOL(acpi_get_timer_resolution)
 48
 49/******************************************************************************
 50 *
 51 * FUNCTION:    acpi_get_timer
 52 *
 53 * PARAMETERS:  ticks               - Where the timer value is returned
 54 *
 55 * RETURN:      Status and current timer value (ticks)
 56 *
 57 * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
 58 *
 59 ******************************************************************************/
 60acpi_status acpi_get_timer(u32 * ticks)
 61{
 62	acpi_status status;
 63	u64 timer_value;
 64
 65	ACPI_FUNCTION_TRACE(acpi_get_timer);
 66
 67	if (!ticks) {
 68		return_ACPI_STATUS(AE_BAD_PARAMETER);
 69	}
 70
 71	/* ACPI 5.0A: PM Timer is optional */
 72
 73	if (!acpi_gbl_FADT.xpm_timer_block.address) {
 74		return_ACPI_STATUS(AE_SUPPORT);
 75	}
 76
 77	status = acpi_hw_read(&timer_value, &acpi_gbl_FADT.xpm_timer_block);
 78	if (ACPI_SUCCESS(status)) {
 79
 80		/* ACPI PM Timer is defined to be 32 bits (PM_TMR_LEN) */
 81
 82		*ticks = (u32)timer_value;
 83	}
 84
 85	return_ACPI_STATUS(status);
 86}
 87
 88ACPI_EXPORT_SYMBOL(acpi_get_timer)
 89
 90/******************************************************************************
 91 *
 92 * FUNCTION:    acpi_get_timer_duration
 93 *
 94 * PARAMETERS:  start_ticks         - Starting timestamp
 95 *              end_ticks           - End timestamp
 96 *              time_elapsed        - Where the elapsed time is returned
 97 *
 98 * RETURN:      Status and time_elapsed
 99 *
100 * DESCRIPTION: Computes the time elapsed (in microseconds) between two
101 *              PM Timer time stamps, taking into account the possibility of
102 *              rollovers, the timer resolution, and timer frequency.
103 *
104 *              The PM Timer's clock ticks at roughly 3.6 times per
105 *              _microsecond_, and its clock continues through Cx state
106 *              transitions (unlike many CPU timestamp counters) -- making it
107 *              a versatile and accurate timer.
108 *
109 *              Note that this function accommodates only a single timer
110 *              rollover. Thus for 24-bit timers, this function should only
111 *              be used for calculating durations less than ~4.6 seconds
112 *              (~20 minutes for 32-bit timers) -- calculations below:
113 *
114 *              2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
115 *              2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
116 *
117 ******************************************************************************/
118acpi_status
119acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 *time_elapsed)
120{
121	acpi_status status;
122	u64 delta_ticks;
123	u64 quotient;
124
125	ACPI_FUNCTION_TRACE(acpi_get_timer_duration);
126
127	if (!time_elapsed) {
128		return_ACPI_STATUS(AE_BAD_PARAMETER);
129	}
130
131	/* ACPI 5.0A: PM Timer is optional */
132
133	if (!acpi_gbl_FADT.xpm_timer_block.address) {
134		return_ACPI_STATUS(AE_SUPPORT);
135	}
136
137	if (start_ticks == end_ticks) {
138		*time_elapsed = 0;
139		return_ACPI_STATUS(AE_OK);
140	}
141
142	/*
143	 * Compute Tick Delta:
144	 * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
145	 */
146	delta_ticks = end_ticks;
147	if (start_ticks > end_ticks) {
148		if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
149
150			/* 24-bit Timer */
151
152			delta_ticks |= (u64)1 << 24;
153		} else {
154			/* 32-bit Timer */
155
156			delta_ticks |= (u64)1 << 32;
157		}
158	}
159	delta_ticks -= start_ticks;
160
161	/*
162	 * Compute Duration (Requires a 64-bit multiply and divide):
163	 *
164	 * time_elapsed (microseconds) =
165	 *  (delta_ticks * ACPI_USEC_PER_SEC) / ACPI_PM_TIMER_FREQUENCY;
166	 */
167	status = acpi_ut_short_divide(delta_ticks * ACPI_USEC_PER_SEC,
168				      ACPI_PM_TIMER_FREQUENCY, &quotient, NULL);
169
170	*time_elapsed = (u32)quotient;
171	return_ACPI_STATUS(status);
172}
173
174ACPI_EXPORT_SYMBOL(acpi_get_timer_duration)
175#endif				/* !ACPI_REDUCED_HARDWARE */