From c8f4049a367f0384549b5c5907603222370664cb Mon Sep 17 00:00:00 2001
From: reinelt <reinelt@3ae390bd-cb1e-0410-b409-cd5a39f66f1f>
Date: Sat, 15 Apr 2000 16:56:52 +0000
Subject: [lcd4linux @ 2000-04-15 16:56:52 by reinelt] moved delay loops to
 udelay.c renamed -d (debugging) switch to -v (verbose) new switch -d to
 calibrate delay loop 'Delay' entry for HD44780 back again delay loops will
 not calibrate automatically, because this will fail with hich CPU load

git-svn-id: https://ssl.bulix.org/svn/lcd4linux/trunk@47 3ae390bd-cb1e-0410-b409-cd5a39f66f1f
---
 udelay.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 udelay.c

(limited to 'udelay.c')

diff --git a/udelay.c b/udelay.c
new file mode 100644
index 0000000..8bb25ab
--- /dev/null
+++ b/udelay.c
@@ -0,0 +1,99 @@
+/* $Id: udelay.c,v 1.1 2000/04/15 16:56:52 reinelt Exp $
+ *
+ * short delays
+ *
+ * Copyright 1999, 2000 by Michael Reinelt (reinelt@eunet.at)
+ *
+ * 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, 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ *
+ * $Log: udelay.c,v $
+ * Revision 1.1  2000/04/15 16:56:52  reinelt
+ *
+ * moved delay loops to udelay.c
+ * renamed -d (debugging) switch to -v (verbose)
+ * new switch -d to calibrate delay loop
+ * 'Delay' entry for HD44780 back again
+ * delay loops will not calibrate automatically, because this will fail with hich CPU load
+ *
+ */
+
+/* 
+ *
+ * exported fuctions:
+ *
+ * void udelay (unsigned long usec)
+ *  delays program execution for usec microseconds
+ *  uses global variable 'loops_per_usec', which has to be set before.
+ *  This function does busy-waiting! so use only for delays smaller
+ *  than 10 msec
+ *
+ * void udelay_calibrate (void)
+ *   does a binary approximation for 'loops_per_usec'
+ *   should be called several times on an otherwise idle machine
+ *   the maximum value should be used
+ *
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>
+
+#include "debug.h"
+#include "udelay.h"
+
+unsigned long loops_per_usec;
+
+void udelay (unsigned long usec)
+{
+  unsigned long loop=usec*loops_per_usec;
+  
+  __asm__ (".align 16\n"
+	   "1:\tdecl %0\n"
+	   "\tjne 1b"
+	   : /* no result */ 
+	   :"a" (loop));
+}
+
+
+/* adopted from /usr/src/linux/init/main.c */
+
+void udelay_calibrate (void)
+{
+  clock_t tick;
+  unsigned long bit;
+  
+  loops_per_usec=1;
+  while (loops_per_usec<<=1) {
+    tick=clock();
+    while (clock()==tick);
+    tick=clock();
+    udelay(1000000/CLOCKS_PER_SEC);
+    if (clock()>tick)
+      break;
+  }
+  
+  loops_per_usec>>=1;
+  bit=loops_per_usec;
+  while (bit>>=1) {
+    loops_per_usec|=bit;
+    tick=clock();
+    while (clock()==tick);
+    tick=clock();
+    udelay(1000000/CLOCKS_PER_SEC);
+    if (clock()>tick)
+      loops_per_usec&=~bit;
+  }
+}
-- 
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