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/*
* Copyright (C) 2008 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
FILE_LICENCE ( GPL2_OR_LATER );
#include <limits.h>
#include <assert.h>
#include <unistd.h>
#include <gpxe/timer.h>
#include <gpxe/efi/efi.h>
#include <gpxe/efi/Protocol/Cpu.h>
/** @file
*
* gPXE timer API for EFI
*
*/
/** Scale factor to apply to CPU timer 0
*
* The timer is scaled down in order to ensure that reasonable values
* for "number of ticks" don't exceed the size of an unsigned long.
*/
#define EFI_TIMER0_SHIFT 12
/** Calibration time */
#define EFI_CALIBRATE_DELAY_MS 1
/** CPU protocol */
static EFI_CPU_ARCH_PROTOCOL *cpu_arch;
EFI_REQUIRE_PROTOCOL ( EFI_CPU_ARCH_PROTOCOL, &cpu_arch );
/**
* Delay for a fixed number of microseconds
*
* @v usecs Number of microseconds for which to delay
*/
static void efi_udelay ( unsigned long usecs ) {
EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
EFI_STATUS efirc;
if ( ( efirc = bs->Stall ( usecs ) ) != 0 ) {
DBG ( "EFI could not delay for %ldus: %s\n",
usecs, efi_strerror ( efirc ) );
/* Probably screwed */
}
}
/**
* Get current system time in ticks
*
* @ret ticks Current time, in ticks
*/
static unsigned long efi_currticks ( void ) {
UINT64 time;
EFI_STATUS efirc;
/* Read CPU timer 0 (TSC) */
if ( ( efirc = cpu_arch->GetTimerValue ( cpu_arch, 0, &time,
NULL ) ) != 0 ) {
DBG ( "EFI could not read CPU timer: %s\n",
efi_strerror ( efirc ) );
/* Probably screwed */
return -1UL;
}
return ( time >> EFI_TIMER0_SHIFT );
}
/**
* Get number of ticks per second
*
* @ret ticks_per_sec Number of ticks per second
*/
static unsigned long efi_ticks_per_sec ( void ) {
static unsigned long ticks_per_sec = 0;
/* Calibrate timer, if necessary. EFI does nominally provide
* the timer speed via the (optional) TimerPeriod parameter to
* the GetTimerValue() call, but it gets the speed slightly
* wrong. By up to three orders of magnitude. Not helpful.
*/
if ( ! ticks_per_sec ) {
unsigned long start;
unsigned long elapsed;
DBG ( "Calibrating EFI timer with a %d ms delay\n",
EFI_CALIBRATE_DELAY_MS );
start = currticks();
mdelay ( EFI_CALIBRATE_DELAY_MS );
elapsed = ( currticks() - start );
ticks_per_sec = ( elapsed * ( 1000 / EFI_CALIBRATE_DELAY_MS ));
DBG ( "EFI CPU timer calibrated at %ld ticks in %d ms (%ld "
"ticks/sec)\n", elapsed, EFI_CALIBRATE_DELAY_MS,
ticks_per_sec );
}
return ticks_per_sec;
}
PROVIDE_TIMER ( efi, udelay, efi_udelay );
PROVIDE_TIMER ( efi, currticks, efi_currticks );
PROVIDE_TIMER ( efi, ticks_per_sec, efi_ticks_per_sec );
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