mirror of https://github.com/ipxe/ipxe.git
137 lines
3.5 KiB
C
137 lines
3.5 KiB
C
/*
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* Copyright (C) 2018 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*
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* You can also choose to distribute this program under the terms of
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* the Unmodified Binary Distribution Licence (as given in the file
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* COPYING.UBDL), provided that you have satisfied its requirements.
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#include <unistd.h>
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#include <errno.h>
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#include <assert.h>
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#include <byteswap.h>
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#include <ipxe/io.h>
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#include <ipxe/acpi.h>
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/** @file
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*
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* ACPI power management timer
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*
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*/
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/** ACPI timer frequency (fixed 3.579545MHz) */
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#define ACPI_TIMER_HZ 3579545
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/** ACPI timer mask
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*
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* Timers may be implemented as either 24-bit or 32-bit counters. We
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* simplify the code by pessimistically assuming that the timer has
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* only 24 bits.
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*/
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#define ACPI_TIMER_MASK 0x00ffffffUL
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/** Power management timer register address */
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static unsigned int pm_tmr;
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struct timer acpi_timer __timer ( TIMER_PREFERRED );
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/**
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* Get current system time in ticks
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*
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* @ret ticks Current time, in ticks
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*/
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static unsigned long acpi_currticks ( void ) {
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static unsigned long offset;
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static uint32_t prev;
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uint32_t now;
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/* Read timer and account for wraparound */
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now = ( inl ( pm_tmr ) & ACPI_TIMER_MASK );
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if ( now < prev ) {
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offset += ( ( ACPI_TIMER_MASK + 1 ) /
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( ACPI_TIMER_HZ / TICKS_PER_SEC ) );
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}
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prev = now;
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/* Convert to timer ticks */
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return ( offset + ( now / ( ACPI_TIMER_HZ / TICKS_PER_SEC ) ) );
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}
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/**
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* Delay for a fixed number of microseconds
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*
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* @v usecs Number of microseconds for which to delay
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*/
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static void acpi_udelay ( unsigned long usecs ) {
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uint32_t start;
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uint32_t elapsed;
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uint32_t threshold;
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/* Delay until a suitable number of ticks have elapsed. We do
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* not need to allow for multiple wraparound, since the
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* wraparound period for a 24-bit timer at 3.579545MHz is
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* around 4700000us.
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*/
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start = inl ( pm_tmr );
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threshold = ( ( usecs * ACPI_TIMER_HZ ) / 1000000 );
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do {
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elapsed = ( ( inl ( pm_tmr ) - start ) & ACPI_TIMER_MASK );
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} while ( elapsed < threshold );
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}
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/**
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* Probe ACPI power management timer
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*
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* @ret rc Return status code
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*/
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static int acpi_timer_probe ( void ) {
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struct acpi_fadt fadtab;
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userptr_t fadt;
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unsigned int pm_tmr_blk;
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/* Locate FADT */
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fadt = acpi_find ( FADT_SIGNATURE, 0 );
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if ( ! fadt ) {
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DBGC ( &acpi_timer, "ACPI could not find FADT\n" );
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return -ENOENT;
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}
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/* Read FADT */
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copy_from_user ( &fadtab, fadt, 0, sizeof ( fadtab ) );
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pm_tmr_blk = le32_to_cpu ( fadtab.pm_tmr_blk );
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if ( ! pm_tmr_blk ) {
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DBGC ( &acpi_timer, "ACPI has no timer\n" );
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return -ENOENT;
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}
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/* Record power management timer register address */
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pm_tmr = ( pm_tmr_blk + ACPI_PM_TMR );
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return 0;
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}
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/** ACPI timer */
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struct timer acpi_timer __timer ( TIMER_PREFERRED ) = {
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.name = "acpi",
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.probe = acpi_timer_probe,
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.currticks = acpi_currticks,
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.udelay = acpi_udelay,
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};
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