wdt_at91.c

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00001 /*
00002  * Copyright (C) 2006 by egnite Software GmbH. All rights reserved.
00003  *
00004  * Redistribution and use in source and binary forms, with or without
00005  * modification, are permitted provided that the following conditions
00006  * are met:
00007  *
00008  * 1. Redistributions of source code must retain the above copyright
00009  *    notice, this list of conditions and the following disclaimer.
00010  * 2. Redistributions in binary form must reproduce the above copyright
00011  *    notice, this list of conditions and the following disclaimer in the
00012  *    documentation and/or other materials provided with the distribution.
00013  * 3. Neither the name of the copyright holders nor the names of
00014  *    contributors may be used to endorse or promote products derived
00015  *    from this software without specific prior written permission.
00016  *
00017  * THIS SOFTWARE IS PROVIDED BY EGNITE SOFTWARE GMBH AND CONTRIBUTORS
00018  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00019  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00020  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL EGNITE
00021  * SOFTWARE GMBH OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00022  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00023  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
00024  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
00025  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
00026  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
00027  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00028  * SUCH DAMAGE.
00029  *
00030  * For additional information see http://www.ethernut.de/
00031  *
00032  */
00033 
00034 /*
00035  * $Log: wdt_at91.c,v $
00036  * Revision 1.2  2006/05/25 09:13:22  haraldkipp
00037  * Platform independent watchdog API added.
00038  *
00039  * Revision 1.1  2006/02/23 15:36:35  haraldkipp
00040  * Added support for AT91 watchdog timer.
00041  *
00042  */
00043 
00044 #include <sys/timer.h>
00045 #include <dev/watchdog.h>
00046 
00051 
00052 static ureg_t nested;
00053 
00060 u_long At91WatchDogStart(u_long ms, u_long xmode)
00061 {
00062     u_int cmval;
00063 
00064     At91WatchDogDisable();
00065 
00066     /*
00067      * The watchdog counts down a 16 bit value, of which the upper
00068      * 4 bits are configurable and the lower 12 bits are set to 1.
00069      * Calculate the number of cycles required to count down the
00070      * upper 4 bits.
00071      */
00072     cmval = ((NutGetCpuClock() / 1000) * ms) >> 13;
00073     
00074     /* Check if MCK/8 is slow enough. */
00075     if (cmval < WD_HPCV) {
00076         cmval = (cmval & WD_HPCV) | WD_WDCLKS_MCK8;
00077     }
00078     /* Check if MCK/32 is slow enough. */
00079     else if ((cmval >>= 2) < WD_HPCV) {
00080         cmval = (cmval & WD_HPCV) | WD_WDCLKS_MCK32;
00081     }
00082     /* Check if MCK/128 is slow enough. */
00083     else if ((cmval >>= 2) < WD_HPCV) {
00084         cmval = (cmval & WD_HPCV) | WD_WDCLKS_MCK128;
00085     }
00086     /* Check if MCK/1024 is slow enough. */
00087     else if ((cmval >>= 3) < WD_HPCV) {
00088         cmval = (cmval & WD_HPCV) | WD_WDCLKS_MCK1024;
00089     }
00090     /* Use maximum. */
00091     else {
00092         cmval = WD_HPCV | WD_WDCLKS_MCK1024;
00093     }
00094     outr(WD_CMR, WD_CKEY | cmval);
00095     if (xmode == 0) {
00096         xmode |= WD_RSTEN;
00097     }
00098     At91WatchDogRestart();
00099     outr(WD_OMR, WD_OKEY | WD_WDEN | xmode);
00100     nested = 1;
00101 
00102     return ms;
00103 }
00104 
00111 void At91WatchDogRestart(void)
00112 {
00113     outr(WD_CR, WD_RSTKEY);
00114 }
00115 
00122 void At91WatchDogDisable(void)
00123 {
00124     if (nested) {
00125         nested++;
00126     }
00127     outr(WD_OMR, WD_OKEY | (inr(WD_OMR) & ~WD_WDEN));
00128 }
00129 
00136 void At91WatchDogEnable(void)
00137 {
00138     if (nested > 1 && --nested == 1) {
00139         At91WatchDogRestart();
00140         outr(WD_OMR, WD_OKEY | inr(WD_OMR) | WD_WDEN);
00141     }
00142 }
00143 

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