| /* |
| * 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 ); |
| |
| /** @file |
| * |
| * RDTSC timer |
| * |
| */ |
| |
| #include <assert.h> |
| #include <gpxe/timer.h> |
| #include <gpxe/timer2.h> |
| |
| /** |
| * Number of TSC ticks per microsecond |
| * |
| * This is calibrated on the first use of the timer. |
| */ |
| static unsigned long rdtsc_ticks_per_usec; |
| |
| /** |
| * Delay for a fixed number of microseconds |
| * |
| * @v usecs Number of microseconds for which to delay |
| */ |
| static void rdtsc_udelay ( unsigned long usecs ) { |
| unsigned long start; |
| unsigned long elapsed; |
| |
| /* Sanity guard, since we may divide by this */ |
| if ( ! usecs ) |
| usecs = 1; |
| |
| start = currticks(); |
| if ( rdtsc_ticks_per_usec ) { |
| /* Already calibrated; busy-wait until done */ |
| do { |
| elapsed = ( currticks() - start ); |
| } while ( elapsed < ( usecs * rdtsc_ticks_per_usec ) ); |
| } else { |
| /* Not yet calibrated; use timer2 and calibrate |
| * based on result. |
| */ |
| timer2_udelay ( usecs ); |
| elapsed = ( currticks() - start ); |
| rdtsc_ticks_per_usec = ( elapsed / usecs ); |
| DBG ( "RDTSC timer calibrated: %ld ticks in %ld usecs " |
| "(%ld MHz)\n", elapsed, usecs, |
| ( rdtsc_ticks_per_usec << TSC_SHIFT ) ); |
| } |
| } |
| |
| /** |
| * Get number of ticks per second |
| * |
| * @ret ticks_per_sec Number of ticks per second |
| */ |
| static unsigned long rdtsc_ticks_per_sec ( void ) { |
| |
| /* Calibrate timer, if not already done */ |
| if ( ! rdtsc_ticks_per_usec ) |
| udelay ( 1 ); |
| |
| /* Sanity check */ |
| assert ( rdtsc_ticks_per_usec != 0 ); |
| |
| return ( rdtsc_ticks_per_usec * 1000 * 1000 ); |
| } |
| |
| PROVIDE_TIMER ( rdtsc, udelay, rdtsc_udelay ); |
| PROVIDE_TIMER_INLINE ( rdtsc, currticks ); |
| PROVIDE_TIMER ( rdtsc, ticks_per_sec, rdtsc_ticks_per_sec ); |