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[time] Add support for the ACPI power management timer
Allow the ACPI power management timer to be used if enabled via TIMER_ACPI in config/timer.h. This provides an alternative timer on systems where the standard 8254 PIT is unavailable or unreliable. Signed-off-by: Michael Brown <mcb30@ipxe.org>
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/* | ||
* Copyright (C) 2018 Michael Brown <mbrown@fensystems.co.uk>. | ||
* | ||
* 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 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., 51 Franklin Street, Fifth Floor, Boston, MA | ||
* 02110-1301, USA. | ||
* | ||
* You can also choose to distribute this program under the terms of | ||
* the Unmodified Binary Distribution Licence (as given in the file | ||
* COPYING.UBDL), provided that you have satisfied its requirements. | ||
*/ | ||
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); | ||
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#include <unistd.h> | ||
#include <errno.h> | ||
#include <assert.h> | ||
#include <byteswap.h> | ||
#include <ipxe/io.h> | ||
#include <ipxe/acpi.h> | ||
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/** @file | ||
* | ||
* ACPI power management timer | ||
* | ||
*/ | ||
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/** ACPI timer frequency (fixed 3.579545MHz) */ | ||
#define ACPI_TIMER_HZ 3579545 | ||
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/** ACPI timer mask | ||
* | ||
* Timers may be implemented as either 24-bit or 32-bit counters. We | ||
* simplify the code by pessimistically assuming that the timer has | ||
* only 24 bits. | ||
*/ | ||
#define ACPI_TIMER_MASK 0x00ffffffUL | ||
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/** Power management timer register address */ | ||
static unsigned int pm_tmr; | ||
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struct timer acpi_timer __timer ( TIMER_PREFERRED ); | ||
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/** | ||
* Get current system time in ticks | ||
* | ||
* @ret ticks Current time, in ticks | ||
*/ | ||
static unsigned long acpi_currticks ( void ) { | ||
static unsigned long offset; | ||
static uint32_t prev; | ||
uint32_t now; | ||
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/* Read timer and account for wraparound */ | ||
now = ( inl ( pm_tmr ) & ACPI_TIMER_MASK ); | ||
if ( now < prev ) { | ||
offset += ( ( ACPI_TIMER_MASK + 1 ) / | ||
( ACPI_TIMER_HZ / TICKS_PER_SEC ) ); | ||
} | ||
prev = now; | ||
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/* Convert to timer ticks */ | ||
return ( offset + ( now / ( ACPI_TIMER_HZ / TICKS_PER_SEC ) ) ); | ||
} | ||
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/** | ||
* Delay for a fixed number of microseconds | ||
* | ||
* @v usecs Number of microseconds for which to delay | ||
*/ | ||
static void acpi_udelay ( unsigned long usecs ) { | ||
uint32_t start; | ||
uint32_t elapsed; | ||
uint32_t threshold; | ||
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/* Delay until a suitable number of ticks have elapsed. We do | ||
* not need to allow for multiple wraparound, since the | ||
* wraparound period for a 24-bit timer at 3.579545MHz is | ||
* around 4700000us. | ||
*/ | ||
start = inl ( pm_tmr ); | ||
threshold = ( ( usecs * ACPI_TIMER_HZ ) / 1000000 ); | ||
do { | ||
elapsed = ( ( inl ( pm_tmr ) - start ) & ACPI_TIMER_MASK ); | ||
} while ( elapsed < threshold ); | ||
} | ||
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/** | ||
* Probe ACPI power management timer | ||
* | ||
* @ret rc Return status code | ||
*/ | ||
static int acpi_timer_probe ( void ) { | ||
struct acpi_fadt fadtab; | ||
userptr_t fadt; | ||
unsigned int pm_tmr_blk; | ||
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/* Locate FADT */ | ||
fadt = acpi_find ( FADT_SIGNATURE, 0 ); | ||
if ( ! fadt ) { | ||
DBGC ( &acpi_timer, "ACPI could not find FADT\n" ); | ||
return -ENOENT; | ||
} | ||
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/* Read FADT */ | ||
copy_from_user ( &fadtab, fadt, 0, sizeof ( fadtab ) ); | ||
pm_tmr_blk = le32_to_cpu ( fadtab.pm_tmr_blk ); | ||
if ( ! pm_tmr_blk ) { | ||
DBGC ( &acpi_timer, "ACPI has no timer\n" ); | ||
return -ENOENT; | ||
} | ||
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/* Record power management timer register address */ | ||
pm_tmr = ( pm_tmr_blk + ACPI_PM_TMR ); | ||
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return 0; | ||
} | ||
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/** ACPI timer */ | ||
struct timer acpi_timer __timer ( TIMER_PREFERRED ) = { | ||
.name = "acpi", | ||
.probe = acpi_timer_probe, | ||
.currticks = acpi_currticks, | ||
.udelay = acpi_udelay, | ||
}; |
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