Basic memory test

apps/memtest/barr_memtest.c

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+/**********************************************************************
+ *
+ * Filename:    memtest.c
+ * 
+ * Description: General-purpose memory testing functions.
+ *
+ * Notes:       This software can be easily ported to systems with
+ *              different data bus widths by redefining 'datum'.
+ *
+ * 
+ * Copyright (c) 1998 by Michael Barr.  This software is placed into
+ * the public domain and may be used for any purpose.  However, this
+ * notice must not be changed or removed and no warranty is either
+ * expressed or implied by its publication or distribution.
+ **********************************************************************/
+
+
+#include "barr_memtest.h"
+
+
+/**********************************************************************
+ *
+ * Function:    memTestDataBus()
+ *
+ * Description: Test the data bus wiring in a memory region by
+ *              performing a walking 1's test at a fixed address
+ *              within that region.  The address (and hence the
+ *              memory region) is selected by the caller.
+ *
+ * Notes:       
+ *
+ * Returns:     0 if the test succeeds.  
+ *              A non-zero result is the first pattern that failed.
+ *
+ **********************************************************************/
+datum
+memTestDataBus(volatile datum * address)
+{
+    datum pattern;
+
+
+    /*
+     * Perform a walking 1's test at the given address.
+     */
+    for (pattern = 1; pattern != 0; pattern <<= 1)
+    {
+        /*
+         * Write the test pattern.
+         */
+        *address = pattern;
+
+        /*
+         * Read it back (immediately is okay for this test).
+         */
+        if (*address != pattern) 
+        {
+            return (pattern);
+        }
+    }
+
+    return (0);
+
+}   /* memTestDataBus() */
+
+
+/**********************************************************************
+ *
+ * Function:    memTestAddressBus()
+ *
+ * Description: Test the address bus wiring in a memory region by
+ *              performing a walking 1's test on the relevant bits
+ *              of the address and checking for aliasing. This test
+ *              will find single-bit address failures such as stuck
+ *              -high, stuck-low, and shorted pins.  The base address
+ *              and size of the region are selected by the caller.
+ *
+ * Notes:       For best results, the selected base address should
+ *              have enough LSB 0's to guarantee single address bit
+ *              changes.  For example, to test a 64-Kbyte region, 
+ *              select a base address on a 64-Kbyte boundary.  Also, 
+ *              select the region size as a power-of-two--if at all 
+ *              possible.
+ *
+ * Returns:     NULL if the test succeeds.  
+ *              A non-zero result is the first address at which an
+ *              aliasing problem was uncovered.  By examining the
+ *              contents of memory, it may be possible to gather
+ *              additional information about the problem.
+ *
+ **********************************************************************/
+datum * 
+memTestAddressBus(volatile datum * baseAddress, unsigned long nBytes)
+{
+    unsigned long addressMask = (nBytes/sizeof(datum) - 1);
+    unsigned long offset;
+    unsigned long testOffset;
+
+    datum pattern     = (datum) 0xAAAAAAAA;
+    datum antipattern = (datum) 0x55555555;
+
+
+    /*
+     * Write the default pattern at each of the power-of-two offsets.
+     */
+    for (offset = 1; (offset & addressMask) != 0; offset <<= 1)
+    {
+        baseAddress[offset] = pattern;
+    }
+
+    /* 
+     * Check for address bits stuck high.
+     */
+    testOffset = 0;
+    baseAddress[testOffset] = antipattern;
+
+    for (offset = 1; (offset & addressMask) != 0; offset <<= 1)
+    {
+        if (baseAddress[offset] != pattern)
+        {
+            return ((datum *) &baseAddress[offset]);
+        }
+    }
+
+    baseAddress[testOffset] = pattern;
+
+    /*
+     * Check for address bits stuck low or shorted.
+     */
+    for (testOffset = 1; (testOffset & addressMask) != 0; testOffset <<= 1)
+    {
+        baseAddress[testOffset] = antipattern;
+
+		if (baseAddress[0] != pattern)
+		{
+			return ((datum *) &baseAddress[testOffset]);
+		}
+
+        for (offset = 1; (offset & addressMask) != 0; offset <<= 1)
+        {
+            if ((baseAddress[offset] != pattern) && (offset != testOffset))
+            {
+                return ((datum *) &baseAddress[testOffset]);
+            }
+        }
+
+        baseAddress[testOffset] = pattern;
+    }
+
+    return (NULL);
+
+}   /* memTestAddressBus() */
+
+
+/**********************************************************************
+ *
+ * Function:    memTestDevice()
+ *
+ * Description: Test the integrity of a physical memory device by
+ *              performing an increment/decrement test over the
+ *              entire region.  In the process every storage bit 
+ *              in the device is tested as a zero and a one.  The
+ *              base address and the size of the region are
+ *              selected by the caller.
+ *
+ * Notes:       
+ *
+ * Returns:     NULL if the test succeeds.
+ *
+ *              A non-zero result is the first address at which an
+ *              incorrect value was read back.  By examining the
+ *              contents of memory, it may be possible to gather
+ *              additional information about the problem.
+ *
+ **********************************************************************/
+datum * 
+memTestDevice(volatile datum * baseAddress, unsigned long nBytes)	
+{
+    unsigned long offset;
+    unsigned long nWords = nBytes / sizeof(datum);
+
+    datum pattern;
+    datum antipattern;
+
+
+    /*
+     * Fill memory with a known pattern.
+     */
+    for (pattern = 1, offset = 0; offset < nWords; pattern++, offset++)
+    {
+        baseAddress[offset] = pattern;
+    }
+
+    /*
+     * Check each location and invert it for the second pass.
+     */
+    for (pattern = 1, offset = 0; offset < nWords; pattern++, offset++)
+    {
+        if (baseAddress[offset] != pattern)
+        {
+            return ((datum *) &baseAddress[offset]);
+        }
+
+        antipattern = ~pattern;
+        baseAddress[offset] = antipattern;
+    }
+
+    /*
+     * Check each location for the inverted pattern and zero it.
+     */
+    for (pattern = 1, offset = 0; offset < nWords; pattern++, offset++)
+    {
+        antipattern = ~pattern;
+        if (baseAddress[offset] != antipattern)
+        {
+            return ((datum *) &baseAddress[offset]);
+        }
+    }
+
+    return (NULL);
+
+}   /* memTestDevice() */