2 * This file is part of the flashrom project.
4 * Copyright (C) 2000 Silicon Integrated System Corporation
5 * Copyright (C) 2009,2010 Carl-Daniel Hailfinger
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 #ifndef __LIBPAYLOAD__
30 /* loops per microsecond */
31 static unsigned long micro = 1;
33 __attribute__ ((noinline)) void myusec_delay(int usecs)
36 for (i = 0; i < usecs * micro; i++) {
37 /* Make sure the compiler doesn't optimize the loop away. */
38 asm volatile ("" : : "rm" (i) );
42 static unsigned long measure_os_delay_resolution(void)
44 unsigned long timeusec;
45 struct timeval start, end;
46 unsigned long counter = 0;
48 gettimeofday(&start, NULL);
51 while (!timeusec && (++counter < 1000000000)) {
52 gettimeofday(&end, NULL);
53 timeusec = 1000000 * (end.tv_sec - start.tv_sec) +
54 (end.tv_usec - start.tv_usec);
55 /* Protect against time going forward too much. */
56 if ((end.tv_sec > start.tv_sec) &&
57 ((end.tv_sec - start.tv_sec) >= LONG_MAX / 1000000 - 1))
59 /* Protect against time going backwards during leap seconds. */
60 if ((end.tv_sec < start.tv_sec) || (timeusec > LONG_MAX))
66 static unsigned long measure_delay(int usecs)
68 unsigned long timeusec;
69 struct timeval start, end;
71 gettimeofday(&start, NULL);
73 gettimeofday(&end, NULL);
74 timeusec = 1000000 * (end.tv_sec - start.tv_sec) +
75 (end.tv_usec - start.tv_usec);
76 /* Protect against time going forward too much. */
77 if ((end.tv_sec > start.tv_sec) &&
78 ((end.tv_sec - start.tv_sec) >= LONG_MAX / 1000000 - 1))
80 /* Protect against time going backwards during leap seconds. */
81 if ((end.tv_sec < start.tv_sec) || (timeusec > LONG_MAX))
87 void myusec_calibrate_delay(void)
89 unsigned long count = 1000;
90 unsigned long timeusec, resolution;
93 msg_pinfo("Calibrating delay loop... ");
94 resolution = measure_os_delay_resolution();
96 msg_pdbg("OS timer resolution is %lu usecs, ", resolution);
98 msg_pinfo("OS timer resolution is unusable. ");
104 timeusec = measure_delay(count);
105 if (timeusec > 1000000 / 4)
107 if (count >= ULONG_MAX / 2) {
108 msg_pinfo("timer loop overflow, reduced precision. ");
115 /* Avoid division by zero, but in that case the loop is shot anyway. */
119 /* Compute rounded up number of loops per microsecond. */
120 micro = (count * micro) / timeusec + 1;
121 msg_pdbg("%luM loops per second, ", micro);
123 /* Did we try to recalibrate less than 5 times? */
125 /* Recheck our timing to make sure we weren't just hitting
126 * a scheduler delay or something similar.
128 for (i = 0; i < 4; i++) {
129 if (resolution && (resolution < 10)) {
130 timeusec = measure_delay(100);
131 } else if (resolution &&
132 (resolution < ULONG_MAX / 200)) {
133 timeusec = measure_delay(resolution * 10) *
134 100 / (resolution * 10);
136 /* This workaround should be active for broken
137 * OS and maybe libpayload. The criterion
138 * here is horrible or non-measurable OS timer
139 * resolution which will result in
140 * measure_delay(100)=0 whereas a longer delay
141 * (1000 ms) may be sufficient
142 * to get a nonzero time measurement.
144 timeusec = measure_delay(1000000) / 10000;
147 msg_pdbg("delay more than 10%% too short (got "
148 "%lu%% of expected delay), "
149 "recalculating... ", timeusec);
154 msg_perr("delay loop is unreliable, trying to continue ");
157 /* We're interested in the actual precision. */
158 timeusec = measure_delay(10);
159 msg_pdbg("10 myus = %ld us, ", timeusec);
160 timeusec = measure_delay(100);
161 msg_pdbg("100 myus = %ld us, ", timeusec);
162 timeusec = measure_delay(1000);
163 msg_pdbg("1000 myus = %ld us, ", timeusec);
164 timeusec = measure_delay(10000);
165 msg_pdbg("10000 myus = %ld us, ", timeusec);
166 timeusec = measure_delay(resolution * 4);
167 msg_pdbg("%ld myus = %ld us, ", resolution * 4, timeusec);
172 void internal_delay(int usecs)
174 /* If the delay is >1 s, use usleep because timing does not need to
177 if (usecs > 1000000) {
185 #include <libpayload.h>
187 void myusec_calibrate_delay(void)
192 void internal_delay(int usecs)