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author | Timothy Pearson <tpearson@raptorengineering.com> | 2016-08-26 16:22:19 -0500 |
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committer | Timothy Pearson <tpearson@raptorengineering.com> | 2016-08-26 16:22:19 -0500 |
commit | 3bac020ef83294fd7c3d40c8ec9c0097da93b876 (patch) | |
tree | 865460b93d760a55ac8eecc20d6019d4a1cb6afa /udelay.c | |
download | flashrom-raptor-p9-3bac020ef83294fd7c3d40c8ec9c0097da93b876.tar.gz flashrom-raptor-p9-3bac020ef83294fd7c3d40c8ec9c0097da93b876.zip |
Stock SVN revision r1954
Diffstat (limited to 'udelay.c')
-rw-r--r-- | udelay.c | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/udelay.c b/udelay.c new file mode 100644 index 0000000..7c6961d --- /dev/null +++ b/udelay.c @@ -0,0 +1,209 @@ +/* + * This file is part of the flashrom project. + * + * Copyright (C) 2000 Silicon Integrated System Corporation + * Copyright (C) 2009,2010 Carl-Daniel Hailfinger + * + * 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 + * (at your option) 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 St, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#ifndef __LIBPAYLOAD__ + +#include <unistd.h> +#include <time.h> +#include <sys/time.h> +#include <stdlib.h> +#include <limits.h> +#include "flash.h" + +/* loops per microsecond */ +static unsigned long micro = 1; + +__attribute__ ((noinline)) void myusec_delay(unsigned int usecs) +{ + unsigned long i; + for (i = 0; i < usecs * micro; i++) { + /* Make sure the compiler doesn't optimize the loop away. */ + __asm__ volatile ("" : : "rm" (i) ); + } +} + +static unsigned long measure_os_delay_resolution(void) +{ + unsigned long timeusec; + struct timeval start, end; + unsigned long counter = 0; + + gettimeofday(&start, NULL); + timeusec = 0; + + while (!timeusec && (++counter < 1000000000)) { + gettimeofday(&end, NULL); + timeusec = 1000000 * (end.tv_sec - start.tv_sec) + + (end.tv_usec - start.tv_usec); + /* Protect against time going forward too much. */ + if ((end.tv_sec > start.tv_sec) && + ((end.tv_sec - start.tv_sec) >= LONG_MAX / 1000000 - 1)) + timeusec = 0; + /* Protect against time going backwards during leap seconds. */ + if ((end.tv_sec < start.tv_sec) || (timeusec > LONG_MAX)) + timeusec = 0; + } + return timeusec; +} + +static unsigned long measure_delay(unsigned int usecs) +{ + unsigned long timeusec; + struct timeval start, end; + + gettimeofday(&start, NULL); + myusec_delay(usecs); + gettimeofday(&end, NULL); + timeusec = 1000000 * (end.tv_sec - start.tv_sec) + + (end.tv_usec - start.tv_usec); + /* Protect against time going forward too much. */ + if ((end.tv_sec > start.tv_sec) && + ((end.tv_sec - start.tv_sec) >= LONG_MAX / 1000000 - 1)) + timeusec = LONG_MAX; + /* Protect against time going backwards during leap seconds. */ + if ((end.tv_sec < start.tv_sec) || (timeusec > LONG_MAX)) + timeusec = 1; + + return timeusec; +} + +void myusec_calibrate_delay(void) +{ + unsigned long count = 1000; + unsigned long timeusec, resolution; + int i, tries = 0; + + msg_pinfo("Calibrating delay loop... "); + resolution = measure_os_delay_resolution(); + if (resolution) { + msg_pdbg("OS timer resolution is %lu usecs, ", resolution); + } else { + msg_pinfo("OS timer resolution is unusable. "); + } + +recalibrate: + count = 1000; + while (1) { + timeusec = measure_delay(count); + if (timeusec > 1000000 / 4) + break; + if (count >= ULONG_MAX / 2) { + msg_pinfo("timer loop overflow, reduced precision. "); + break; + } + count *= 2; + } + tries ++; + + /* Avoid division by zero, but in that case the loop is shot anyway. */ + if (!timeusec) + timeusec = 1; + + /* Compute rounded up number of loops per microsecond. */ + micro = (count * micro) / timeusec + 1; + msg_pdbg("%luM loops per second, ", micro); + + /* Did we try to recalibrate less than 5 times? */ + if (tries < 5) { + /* Recheck our timing to make sure we weren't just hitting + * a scheduler delay or something similar. + */ + for (i = 0; i < 4; i++) { + if (resolution && (resolution < 10)) { + timeusec = measure_delay(100); + } else if (resolution && + (resolution < ULONG_MAX / 200)) { + timeusec = measure_delay(resolution * 10) * + 100 / (resolution * 10); + } else { + /* This workaround should be active for broken + * OS and maybe libpayload. The criterion + * here is horrible or non-measurable OS timer + * resolution which will result in + * measure_delay(100)=0 whereas a longer delay + * (1000 ms) may be sufficient + * to get a nonzero time measurement. + */ + timeusec = measure_delay(1000000) / 10000; + } + if (timeusec < 90) { + msg_pdbg("delay more than 10%% too short (got " + "%lu%% of expected delay), " + "recalculating... ", timeusec); + goto recalibrate; + } + } + } else { + msg_perr("delay loop is unreliable, trying to continue "); + } + + /* We're interested in the actual precision. */ + timeusec = measure_delay(10); + msg_pdbg("10 myus = %ld us, ", timeusec); + timeusec = measure_delay(100); + msg_pdbg("100 myus = %ld us, ", timeusec); + timeusec = measure_delay(1000); + msg_pdbg("1000 myus = %ld us, ", timeusec); + timeusec = measure_delay(10000); + msg_pdbg("10000 myus = %ld us, ", timeusec); + timeusec = measure_delay(resolution * 4); + msg_pdbg("%ld myus = %ld us, ", resolution * 4, timeusec); + + msg_pinfo("OK.\n"); +} + +/* Not very precise sleep. */ +void internal_sleep(unsigned int usecs) +{ +#if IS_WINDOWS + Sleep((usecs + 999) / 1000); +#elif defined(__DJGPP__) + sleep(usecs / 1000000); + usleep(usecs % 1000000); +#else + nanosleep(&(struct timespec){usecs / 1000000, (usecs * 1000) % 1000000000UL}, NULL); +#endif +} + +/* Precise delay. */ +void internal_delay(unsigned int usecs) +{ + /* If the delay is >1 s, use internal_sleep because timing does not need to be so precise. */ + if (usecs > 1000000) { + internal_sleep(usecs); + } else { + myusec_delay(usecs); + } +} + +#else +#include <libpayload.h> + +void myusec_calibrate_delay(void) +{ + get_cpu_speed(); +} + +void internal_delay(unsigned int usecs) +{ + udelay(usecs); +} +#endif |