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Diffstat (limited to 'drivers/acpi/hardware/hwtimer.c')
| -rw-r--r-- | drivers/acpi/hardware/hwtimer.c | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/drivers/acpi/hardware/hwtimer.c b/drivers/acpi/hardware/hwtimer.c new file mode 100644 index 000000000..b7f529ccf --- /dev/null +++ b/drivers/acpi/hardware/hwtimer.c @@ -0,0 +1,196 @@ + +/****************************************************************************** + * + * Name: hwtimer.c - ACPI Power Management Timer Interface + * $Revision: 4 $ + * + *****************************************************************************/ + +/* + * Copyright (C) 2000, 2001 R. Byron Moore + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#include "acpi.h" +#include "achware.h" + +#define _COMPONENT HARDWARE + MODULE_NAME ("hwtimer") + + +/****************************************************************************** + * + * FUNCTION: Acpi_get_timer_resolution + * + * PARAMETERS: none + * + * RETURN: Number of bits of resolution in the PM Timer (24 or 32). + * + * DESCRIPTION: Obtains resolution of the ACPI PM Timer. + * + ******************************************************************************/ + +ACPI_STATUS +acpi_get_timer_resolution ( + u32 *resolution) +{ + if (!resolution) { + return (AE_BAD_PARAMETER); + } + + if (0 == acpi_gbl_FADT->tmr_val_ext) { + *resolution = 24; + } + else { + *resolution = 32; + } + + return (AE_OK); +} + + +/****************************************************************************** + * + * FUNCTION: Acpi_get_timer + * + * PARAMETERS: none + * + * RETURN: Current value of the ACPI PM Timer (in ticks). + * + * DESCRIPTION: Obtains current value of ACPI PM Timer. + * + ******************************************************************************/ + +ACPI_STATUS +acpi_get_timer ( + u32 *ticks) +{ + if (!ticks) { + return (AE_BAD_PARAMETER); + } + + *ticks = acpi_os_in32 ((ACPI_IO_ADDRESS) ACPI_GET_ADDRESS (acpi_gbl_FADT->Xpm_tmr_blk.address)); + + return (AE_OK); +} + + +/****************************************************************************** + * + * FUNCTION: Acpi_get_timer_duration + * + * PARAMETERS: Start_ticks + * End_ticks + * Time_elapsed + * + * RETURN: 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 accomodates 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 hours for 32-bit timers). + * + ******************************************************************************/ + +ACPI_STATUS +acpi_get_timer_duration ( + u32 start_ticks, + u32 end_ticks, + u32 *time_elapsed) +{ + u32 delta_ticks = 0; + u32 seconds = 0; + u32 milliseconds = 0; + u32 microseconds = 0; + u32 remainder = 0; + + if (!time_elapsed) { + return (AE_BAD_PARAMETER); + } + + /* + * Compute Tick Delta: + * ------------------- + * Handle timer rollovers on 24- versus 32-bit timers. + */ + if (start_ticks < end_ticks) { + delta_ticks = end_ticks - start_ticks; + } + else if (start_ticks > end_ticks) { + /* 24-bit Timer */ + if (0 == acpi_gbl_FADT->tmr_val_ext) { + delta_ticks = (0x00FFFFFF - start_ticks) + end_ticks; + } + /* 32-bit Timer */ + else { + delta_ticks = (0xFFFFFFFF - start_ticks) + end_ticks; + } + } + + /* + * Compute Duration: + * ----------------- + * Since certain compilers (gcc/Linux, argh!) don't support 64-bit + * divides in kernel-space we have to do some trickery to preserve + * accuracy while using 32-bit math. + * + * TODO: Change to use 64-bit math when supported. + * + * The process is as follows: + * 1. Compute the number of seconds by dividing Delta Ticks by + * the timer frequency. + * 2. Compute the number of milliseconds in the remainder from step #1 + * by multiplying by 1000 and then dividing by the timer frequency. + * 3. Compute the number of microseconds in the remainder from step #2 + * by multiplying by 1000 and then dividing by the timer frequency. + * 4. Add the results from steps 1, 2, and 3 to get the total duration. + * + * Example: The time elapsed for Delta_ticks = 0xFFFFFFFF should be + * 1199864031 microseconds. This is computed as follows: + * Step #1: Seconds = 1199; Remainder = 3092840 + * Step #2: Milliseconds = 864; Remainder = 113120 + * Step #3: Microseconds = 31; Remainder = <don't care!> + */ + + /* Step #1 */ + seconds = delta_ticks / PM_TIMER_FREQUENCY; + remainder = delta_ticks % PM_TIMER_FREQUENCY; + + /* Step #2 */ + milliseconds = (remainder * 1000) / PM_TIMER_FREQUENCY; + remainder = (remainder * 1000) % PM_TIMER_FREQUENCY; + + /* Step #3 */ + microseconds = (remainder * 1000) / PM_TIMER_FREQUENCY; + + /* Step #4 */ + *time_elapsed = seconds * 1000000; + *time_elapsed += milliseconds * 1000; + *time_elapsed += microseconds; + + return (AE_OK); +} + + |