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/*
* 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
*/
#include <unistd.h>
#include <sys/time.h>
#include <stdlib.h>
#include <limits.h>
#include "flash.h"
/* loops per microsecond */
unsigned long micro = 1;
__attribute__ ((noinline)) void myusec_delay(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) );
}
}
unsigned long measure_os_delay_resolution(void)
{
unsigned long timeusec;
struct timeval start, end;
unsigned long counter = 0;
gettimeofday(&start, 0);
timeusec = 0;
while (!timeusec && (++counter < 1000000000)) {
gettimeofday(&end, 0);
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;
}
unsigned long measure_delay(int usecs)
{
unsigned long timeusec;
struct timeval start, end;
gettimeofday(&start, 0);
myusec_delay(usecs);
gettimeofday(&end, 0);
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 %u 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");
}
void internal_delay(int usecs)
{
/* If the delay is >1 s, use usleep because timing does not need to
* be so precise.
*/
if (usecs > 1000000) {
usleep(usecs);
} else {
myusec_delay(usecs);
}
}
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