The delay loop is probably one of the oldest pieces of code
Clean up code duplication and measure timing of 10/100/1000/10000 us
delays.
Corresponding to flashrom svn r986.
Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Maciej Pijanka <maciej.pijanka@gmail.com>
diff --git a/udelay.c b/udelay.c
index f61d793..ac58017 100644
--- a/udelay.c
+++ b/udelay.c
@@ -2,6 +2,7 @@
* 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
@@ -19,6 +20,8 @@
*/
#include <sys/time.h>
+#include <stdlib.h>
+#include <limits.h>
#include "flash.h"
// count to a billion. Time it. If it's < 1 sec, count to 10B, etc.
@@ -30,21 +33,30 @@
for (i = 0; i < usecs * micro; i++) ;
}
+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);
+
+ return timeusec;
+}
+
void myusec_calibrate_delay(void)
{
int count = 1000;
unsigned long timeusec;
- struct timeval start, end;
int ok = 0;
printf("Calibrating delay loop... ");
while (!ok) {
- gettimeofday(&start, 0);
- myusec_delay(count);
- gettimeofday(&end, 0);
- timeusec = 1000000 * (end.tv_sec - start.tv_sec) +
- (end.tv_usec - start.tv_usec);
+ timeusec = measure_delay(count);
count *= 2;
if (timeusec < 1000000 / 4)
continue;
@@ -53,14 +65,18 @@
// compute one microsecond. That will be count / time
micro = count / timeusec;
+ msg_pdbg("%ldM loops per second, ", micro);
- gettimeofday(&start, 0);
- myusec_delay(100);
- gettimeofday(&end, 0);
- timeusec = 1000000 * (end.tv_sec - start.tv_sec) +
- (end.tv_usec - start.tv_usec);
- printf_debug("%ldM loops per second, 100 myus = %ld us. ",
- (unsigned long)micro, timeusec);
+ /* 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);
+
printf("OK.\n");
}