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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.
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <unistd.h>
#include <errno.h>
#include <assert.h>
#include <byteswap.h>
#include <ipxe/io.h>
#include <ipxe/acpi.h>
/** @file
*
* ACPI power management timer
*
*/
/** ACPI timer frequency (fixed 3.579545MHz) */
#define ACPI_TIMER_HZ 3579545
/** 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
/** Power management timer register address */
static unsigned int pm_tmr;
struct timer acpi_timer __timer ( TIMER_PREFERRED );
/**
* 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;
/* 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;
/* Convert to timer ticks */
return ( offset + ( now / ( ACPI_TIMER_HZ / TICKS_PER_SEC ) ) );
}
/**
* 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;
/* 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 );
}
/**
* 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;
/* Locate FADT */
fadt = acpi_find ( FADT_SIGNATURE, 0 );
if ( ! fadt ) {
DBGC ( &acpi_timer, "ACPI could not find FADT\n" );
return -ENOENT;
}
/* 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;
}
/* Record power management timer register address */
pm_tmr = ( pm_tmr_blk + ACPI_PM_TMR );
return 0;
}
/** 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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