129 lines
3.5 KiB
C
129 lines
3.5 KiB
C
/*
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* Copyright (C) 2008 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 <string.h>
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#include <errno.h>
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#include <limits.h>
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#include <assert.h>
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#include <unistd.h>
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#include <ipxe/timer.h>
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#include <ipxe/efi/efi.h>
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#include <ipxe/efi/Protocol/Cpu.h>
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/** @file
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*
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* iPXE timer API for EFI
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*
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*/
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/** Scale factor to apply to CPU timer 0
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*
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* The timer is scaled down in order to ensure that reasonable values
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* for "number of ticks" don't exceed the size of an unsigned long.
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*/
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#define EFI_TIMER0_SHIFT 12
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/** Calibration time */
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#define EFI_CALIBRATE_DELAY_MS 1
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/** CPU protocol */
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static EFI_CPU_ARCH_PROTOCOL *cpu_arch;
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EFI_REQUIRE_PROTOCOL ( EFI_CPU_ARCH_PROTOCOL, &cpu_arch );
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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 efi_udelay ( unsigned long usecs ) {
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EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
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EFI_STATUS efirc;
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int rc;
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if ( ( efirc = bs->Stall ( usecs ) ) != 0 ) {
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rc = -EEFI ( efirc );
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DBG ( "EFI could not delay for %ldus: %s\n",
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usecs, strerror ( rc ) );
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/* Probably screwed */
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}
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}
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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 efi_currticks ( void ) {
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UINT64 time;
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EFI_STATUS efirc;
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int rc;
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/* Read CPU timer 0 (TSC) */
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if ( ( efirc = cpu_arch->GetTimerValue ( cpu_arch, 0, &time,
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NULL ) ) != 0 ) {
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rc = -EEFI ( efirc );
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DBG ( "EFI could not read CPU timer: %s\n", strerror ( rc ) );
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/* Probably screwed */
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return -1UL;
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}
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return ( time >> EFI_TIMER0_SHIFT );
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}
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/**
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* Get number of ticks per second
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*
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* @ret ticks_per_sec Number of ticks per second
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*/
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static unsigned long efi_ticks_per_sec ( void ) {
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static unsigned long ticks_per_sec = 0;
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/* Calibrate timer, if necessary. EFI does nominally provide
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* the timer speed via the (optional) TimerPeriod parameter to
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* the GetTimerValue() call, but it gets the speed slightly
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* wrong. By up to three orders of magnitude. Not helpful.
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*/
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if ( ! ticks_per_sec ) {
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unsigned long start;
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unsigned long elapsed;
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DBG ( "Calibrating EFI timer with a %d ms delay\n",
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EFI_CALIBRATE_DELAY_MS );
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start = currticks();
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mdelay ( EFI_CALIBRATE_DELAY_MS );
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elapsed = ( currticks() - start );
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ticks_per_sec = ( elapsed * ( 1000 / EFI_CALIBRATE_DELAY_MS ));
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DBG ( "EFI CPU timer calibrated at %ld ticks in %d ms (%ld "
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"ticks/sec)\n", elapsed, EFI_CALIBRATE_DELAY_MS,
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ticks_per_sec );
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}
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return ticks_per_sec;
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}
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PROVIDE_TIMER ( efi, udelay, efi_udelay );
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PROVIDE_TIMER ( efi, currticks, efi_currticks );
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PROVIDE_TIMER ( efi, ticks_per_sec, efi_ticks_per_sec );
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