/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
- // SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
- /******************************************************************************
- *
- * Name: hwtimer.c - ACPI Power Management Timer Interface
- *
- * Copyright (C) 2000 - 2020, Intel Corp.
- *
- *****************************************************************************/
- #define EXPORT_ACPI_INTERFACES
- #include <acpi/acpi.h>
- #include "accommon.h"
- #define _COMPONENT ACPI_HARDWARE
- ACPI_MODULE_NAME("hwtimer")
- #if (!ACPI_REDUCED_HARDWARE) /* Entire module */
- /******************************************************************************
- *
- * FUNCTION: acpi_get_timer_resolution
- *
- * PARAMETERS: resolution - Where the resolution is returned
- *
- * RETURN: Status and timer resolution
- *
- * DESCRIPTION: Obtains resolution of the ACPI PM Timer (24 or 32 bits).
- *
- ******************************************************************************/
- acpi_status acpi_get_timer_resolution(u32 * resolution)
- {
- ACPI_FUNCTION_TRACE(acpi_get_timer_resolution);
- if (!resolution) {
- return_ACPI_STATUS(AE_BAD_PARAMETER);
- }
- if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
- *resolution = 24;
- } else {
- *resolution = 32;
- }
- return_ACPI_STATUS(AE_OK);
- }
- ACPI_EXPORT_SYMBOL(acpi_get_timer_resolution)
- /******************************************************************************
- *
- * FUNCTION: acpi_get_timer
- *
- * PARAMETERS: ticks - Where the timer value is returned
- *
- * RETURN: Status and current timer value (ticks)
- *
- * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
- *
- ******************************************************************************/
- acpi_status acpi_get_timer(u32 * ticks)
- {
- acpi_status status;
- u64 timer_value;
- ACPI_FUNCTION_TRACE(acpi_get_timer);
- if (!ticks) {
- return_ACPI_STATUS(AE_BAD_PARAMETER);
- }
- /* ACPI 5.0A: PM Timer is optional */
- if (!acpi_gbl_FADT.xpm_timer_block.address) {
- return_ACPI_STATUS(AE_SUPPORT);
- }
- status = acpi_hw_read(&timer_value, &acpi_gbl_FADT.xpm_timer_block);
- if (ACPI_SUCCESS(status)) {
- /* ACPI PM Timer is defined to be 32 bits (PM_TMR_LEN) */
- *ticks = (u32)timer_value;
- }
- return_ACPI_STATUS(status);
- }
- ACPI_EXPORT_SYMBOL(acpi_get_timer)
- /******************************************************************************
- *
- * FUNCTION: acpi_get_timer_duration
- *
- * PARAMETERS: start_ticks - Starting timestamp
- * end_ticks - End timestamp
- * time_elapsed - Where the elapsed time is returned
- *
- * RETURN: Status and time_elapsed
- *
- * DESCRIPTION: Computes the time elapsed (in microseconds) between two
- * PM Timer time stamps, taking into account the possibility of
- * rollovers, the timer resolution, and timer frequency.
- *
- * The PM Timer's clock ticks at roughly 3.6 times per
- * _microsecond_, and its clock continues through Cx state
- * transitions (unlike many CPU timestamp counters) -- making it
- * a versatile and accurate timer.
- *
- * Note that this function accommodates only a single timer
- * rollover. Thus for 24-bit timers, this function should only
- * be used for calculating durations less than ~4.6 seconds
- * (~20 minutes for 32-bit timers) -- calculations below:
- *
- * 2**24 Ticks / 3,600,000 Ticks/Sec = 4.66 sec
- * 2**32 Ticks / 3,600,000 Ticks/Sec = 1193 sec or 19.88 minutes
- *
- ******************************************************************************/
- acpi_status
- acpi_get_timer_duration(u32 start_ticks, u32 end_ticks, u32 *time_elapsed)
- {
- acpi_status status;
- u64 delta_ticks;
- u64 quotient;
- ACPI_FUNCTION_TRACE(acpi_get_timer_duration);
- if (!time_elapsed) {
- return_ACPI_STATUS(AE_BAD_PARAMETER);
- }
- /* ACPI 5.0A: PM Timer is optional */
- if (!acpi_gbl_FADT.xpm_timer_block.address) {
- return_ACPI_STATUS(AE_SUPPORT);
- }
- if (start_ticks == end_ticks) {
- *time_elapsed = 0;
- return_ACPI_STATUS(AE_OK);
- }
- /*
- * Compute Tick Delta:
- * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
- */
- delta_ticks = end_ticks;
- if (start_ticks > end_ticks) {
- if ((acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER) == 0) {
- /* 24-bit Timer */
- delta_ticks |= (u64)1 << 24;
- } else {
- /* 32-bit Timer */
- delta_ticks |= (u64)1 << 32;
- }
- }
- delta_ticks -= start_ticks;
- /*
- * Compute Duration (Requires a 64-bit multiply and divide):
- *
- * time_elapsed (microseconds) =
- * (delta_ticks * ACPI_USEC_PER_SEC) / ACPI_PM_TIMER_FREQUENCY;
- */
- status = acpi_ut_short_divide(delta_ticks * ACPI_USEC_PER_SEC,
- ACPI_PM_TIMER_FREQUENCY, "ient, NULL);
- *time_elapsed = (u32)quotient;
- return_ACPI_STATUS(status);
- }
- ACPI_EXPORT_SYMBOL(acpi_get_timer_duration)
- #endif /* !ACPI_REDUCED_HARDWARE */