patch-2.4.1 linux/drivers/acpi/hardware/hwtimer.c

• Lines: 197
• Date: Mon Jan 29 10:15:58 2001
• Orig file: v2.4.0/linux/drivers/acpi/hardware/hwtimer.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.0/linux/drivers/acpi/hardware/hwtimer.c linux/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);
+}
+
+