xref: /openbmc/linux/drivers/acpi/acpica/hwtimer.c (revision 612c2932)

// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
/******************************************************************************
 *
 * Name: hwtimer.c - ACPI Power Management Timer Interface
 *
 * Copyright (C) 2000 - 2023, 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, &quotient, NULL);

	*time_elapsed = (u32)quotient;
	return_ACPI_STATUS(status);
}

ACPI_EXPORT_SYMBOL(acpi_get_timer_duration)
#endif				/* !ACPI_REDUCED_HARDWARE */