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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., 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 );
-
- /** @file
- *
- * RDTSC timer
- *
- */
-
- #include <string.h>
- #include <errno.h>
- #include <ipxe/timer.h>
- #include <ipxe/cpuid.h>
- #include <ipxe/pit8254.h>
-
- /** Number of microseconds to use for TSC calibration */
- #define TSC_CALIBRATE_US 1024
-
- /** TSC increment per microsecond */
- static unsigned long tsc_per_us;
-
- /** Minimum resolution for scaled TSC timer */
- #define TSC_SCALED_HZ 32
-
- /** TSC scale (expressed as a bit shift)
- *
- * We use this to avoid the need for 64-bit divsion on 32-bit systems.
- */
- static unsigned int tsc_scale;
-
- /** Number of timer ticks per scaled TSC increment */
- static unsigned long ticks_per_scaled_tsc;
-
- /** Colour for debug messages */
- #define colour &tsc_per_us
-
- /**
- * Get raw TSC value
- *
- * @ret tsc Raw TSC value
- */
- static inline __always_inline unsigned long rdtsc_raw ( void ) {
- unsigned long raw;
-
- __asm__ __volatile__ ( "rdtsc\n\t" : "=a" ( raw ) : : "edx" );
- return raw;
- }
-
- /**
- * Get TSC value, shifted to avoid rollover within a realistic timescale
- *
- * @ret tsc Scaled TSC value
- */
- static inline __always_inline unsigned long rdtsc_scaled ( void ) {
- unsigned long scaled;
-
- __asm__ __volatile__ ( "rdtsc\n\t"
- "shrdl %b1, %%edx, %%eax\n\t"
- : "=a" ( scaled ) : "c" ( tsc_scale ) : "edx" );
- return scaled;
- }
-
- /**
- * Get current system time in ticks
- *
- * @ret ticks Current time, in ticks
- */
- static unsigned long rdtsc_currticks ( void ) {
- unsigned long scaled;
-
- scaled = rdtsc_scaled();
- return ( scaled * ticks_per_scaled_tsc );
- }
-
- /**
- * 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;
- unsigned long threshold;
-
- start = rdtsc_raw();
- threshold = ( usecs * tsc_per_us );
- do {
- elapsed = ( rdtsc_raw() - start );
- } while ( elapsed < threshold );
- }
-
- /**
- * Probe RDTSC timer
- *
- * @ret rc Return status code
- */
- static int rdtsc_probe ( void ) {
- unsigned long before;
- unsigned long after;
- unsigned long elapsed;
- uint32_t apm;
- uint32_t discard_a;
- uint32_t discard_b;
- uint32_t discard_c;
- int rc;
-
- /* Check that TSC is invariant */
- if ( ( rc = cpuid_supported ( CPUID_APM ) ) != 0 ) {
- DBGC ( colour, "RDTSC cannot determine APM features: %s\n",
- strerror ( rc ) );
- return rc;
- }
- cpuid ( CPUID_APM, 0, &discard_a, &discard_b, &discard_c, &apm );
- if ( ! ( apm & CPUID_APM_EDX_TSC_INVARIANT ) ) {
- DBGC ( colour, "RDTSC has non-invariant TSC (%#08x)\n",
- apm );
- return -ENOTTY;
- }
-
- /* Calibrate udelay() timer via 8254 PIT */
- before = rdtsc_raw();
- pit8254_udelay ( TSC_CALIBRATE_US );
- after = rdtsc_raw();
- elapsed = ( after - before );
- tsc_per_us = ( elapsed / TSC_CALIBRATE_US );
- if ( ! tsc_per_us ) {
- DBGC ( colour, "RDTSC has zero TSC per microsecond\n" );
- return -EIO;
- }
-
- /* Calibrate currticks() scaling factor */
- tsc_scale = 31;
- ticks_per_scaled_tsc = ( ( 1UL << tsc_scale ) /
- ( tsc_per_us * ( 1000000 / TICKS_PER_SEC ) ) );
- while ( ticks_per_scaled_tsc > ( TICKS_PER_SEC / TSC_SCALED_HZ ) ) {
- tsc_scale--;
- ticks_per_scaled_tsc >>= 1;
- }
- DBGC ( colour, "RDTSC has %ld tsc per us, %ld ticks per 2^%d tsc\n",
- tsc_per_us, ticks_per_scaled_tsc, tsc_scale );
- if ( ! ticks_per_scaled_tsc ) {
- DBGC ( colour, "RDTSC has zero ticks per TSC\n" );
- return -EIO;
- }
-
- return 0;
- }
-
- /** RDTSC timer */
- struct timer rdtsc_timer __timer ( TIMER_PREFERRED ) = {
- .name = "rdtsc",
- .probe = rdtsc_probe,
- .currticks = rdtsc_currticks,
- .udelay = rdtsc_udelay,
- };
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