[commit] r986 - trunk

[repository service]

Author: hailfinger
Date: Sat Mar 27 17:16:01 2010
New Revision: 986
URL: http://flashrom.org/trac/coreboot/changeset/986

Log:
The delay loop is probably one of the oldest pieces of code in flashrom.
Clean up code duplication and measure timing of 10/100/1000/10000 us
delays.

Signed-off-by: Carl-Daniel Hailfinger 
Acked-by: Maciej Pijanka

Modified:
   trunk/udelay.c

Modified: trunk/udelay.c
==============================================================================
--- trunk/udelay.c	Fri Mar 26 00:18:41 2010	(r985)
+++ trunk/udelay.c	Sat Mar 27 17:16:01 2010	(r986)
@@ -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);
+
+	/* 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);

-	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);
    printf("OK.\n");
 }