/drivers/acpi/hardware/hwtimer.c
https://bitbucket.org/evzijst/gittest · C · 203 lines · 67 code · 34 blank · 102 comment · 13 complexity · 3cb33fcec85ea33689cd5789d727a708 MD5 · raw file
- /******************************************************************************
- *
- * Name: hwtimer.c - ACPI Power Management Timer Interface
- *
- *****************************************************************************/
- /*
- * Copyright (C) 2000 - 2005, R. Byron Moore
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions, and the following disclaimer,
- * without modification.
- * 2. Redistributions in binary form must reproduce at minimum a disclaimer
- * substantially similar to the "NO WARRANTY" disclaimer below
- * ("Disclaimer") and any redistribution must be conditioned upon
- * including a substantially similar Disclaimer requirement for further
- * binary redistribution.
- * 3. Neither the names of the above-listed copyright holders nor the names
- * of any contributors may be used to endorse or promote products derived
- * from this software without specific prior written permission.
- *
- * Alternatively, this software may be distributed under the terms of the
- * GNU General Public License ("GPL") version 2 as published by the Free
- * Software Foundation.
- *
- * NO WARRANTY
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
- * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
- * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGES.
- */
- #include <linux/module.h>
- #include <acpi/acpi.h>
- #define _COMPONENT ACPI_HARDWARE
- ACPI_MODULE_NAME ("hwtimer")
- /******************************************************************************
- *
- * 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 (0 == acpi_gbl_FADT->tmr_val_ext) {
- *resolution = 24;
- }
- else {
- *resolution = 32;
- }
- return_ACPI_STATUS (AE_OK);
- }
- /******************************************************************************
- *
- * FUNCTION: acpi_get_timer
- *
- * PARAMETERS: Ticks - Where the timer value is returned
- *
- * RETURN: Status and current ticks
- *
- * DESCRIPTION: Obtains current value of ACPI PM Timer (in ticks).
- *
- ******************************************************************************/
- acpi_status
- acpi_get_timer (
- u32 *ticks)
- {
- acpi_status status;
- ACPI_FUNCTION_TRACE ("acpi_get_timer");
- if (!ticks) {
- return_ACPI_STATUS (AE_BAD_PARAMETER);
- }
- status = acpi_hw_low_level_read (32, ticks, &acpi_gbl_FADT->xpm_tmr_blk);
- return_ACPI_STATUS (status);
- }
- 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;
- u32 delta_ticks;
- acpi_integer quotient;
- ACPI_FUNCTION_TRACE ("acpi_get_timer_duration");
- if (!time_elapsed) {
- return_ACPI_STATUS (AE_BAD_PARAMETER);
- }
- /*
- * Compute Tick Delta:
- * Handle (max one) timer rollovers on 24-bit versus 32-bit timers.
- */
- if (start_ticks < end_ticks) {
- delta_ticks = end_ticks - start_ticks;
- }
- else if (start_ticks > end_ticks) {
- if (0 == acpi_gbl_FADT->tmr_val_ext) {
- /* 24-bit Timer */
- delta_ticks = (((0x00FFFFFF - start_ticks) + end_ticks) & 0x00FFFFFF);
- }
- else {
- /* 32-bit Timer */
- delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks;
- }
- }
- else /* start_ticks == end_ticks */ {
- *time_elapsed = 0;
- return_ACPI_STATUS (AE_OK);
- }
- /*
- * Compute Duration (Requires a 64-bit multiply and divide):
- *
- * time_elapsed = (delta_ticks * 1000000) / PM_TIMER_FREQUENCY;
- */
- status = acpi_ut_short_divide (((u64) delta_ticks) * 1000000,
- PM_TIMER_FREQUENCY, "ient, NULL);
- *time_elapsed = (u32) quotient;
- return_ACPI_STATUS (status);
- }
- EXPORT_SYMBOL(acpi_get_timer_duration);