内存测试三步法

1、DDR内存子系统常见硬件错误及Uboot中检测流程在 U-Boot中，Denx（U-Boot的开发商）针对常见的DDR内存故障进行了严格的检测处理，下图描述了该检测处理过程的三个步骤：检测数据线、地址线和DDR物理存储部件，主要涉及这三个步骤的处理过程和方法，对于DDR子系统，是很容易出故障并且是很难debug检测出来的，而Denx所针对 DDR内存故障设计的检测方法是非常严谨，值得学习研究的。下面主要是相关的检测处理思路及问题：1、为什么先检测数据线？因为如果数据线是断开的，那么一切无从谈起！接下来是检测地址线，只有数据线和地址线都通过，检测内存的存储单元才有意义，这样的流程也利于分割定位问

2、题。上面testing sequence框图将整个检测过程分成三大步，用三个虚线方框表示。2、数据线的连接错误数据线的连接可能存在两种错误，一种是被断开，另一种布线或生产造成互相短路。3、如何检测数据线的连接错误4、如何检测数据线与板上其它信号线交叉短路或断路取以上6个pattern的反码，总共12个pattern就能检测到每一位都可以写入和读出0和1。5、什么是floating buses错误floating buses会“欺骗”测试软件，如果测试软件写入并很快读出一个值的时候，写操作会给数据线上的电容充电，总线会短暂的保持它的状态。当测试软件读操作时，总线会返回刚写入的值，即使实际上该数据

3、线是断路的。6、如何检测数据线的floating buses错误检测floating buses错误的算法不复杂，在写入和读回之间再插入一次对不同地址写入不同值的操作。例如，X写入X1位置,Y写入Y1位置，再从X1位置读出X值则表示floating buses错误不存在。7、地址线的错误如果地址线存在错误，其症状是地址空间中的两个不同位置被映射到同一物理存储位置。更通俗地讲，就是写一个位置却“改变”了另一个位置。8、地址线的错误检测地址线的错误检测相对简单，其算法是：1）、将地址的值作为内容写入该地址处，汇编的表示方法是 (addr) = addr。即将地址值写到地址对应的空间里，这样确保每一

4、个位置的内容不同。2）、依次将内存基地址的某一根地址线的值翻转（flip/toggle）得到某个地址，从该地址取值，如果该值和基地址的值相等，则表示某一位地址线有问题。这个算法的特点是每次只检测一根地址线，方法简单有效。9、存储单元的错误以上数据线和地址线的检测都是检测布线或工厂生产的错误，而存储单元的检测则是真正对DDR内存芯片的检测。内存芯片的常见错误是bit-stuck，简而言之，就是让它是0，它偏为1，让它为1，它偏为0，检测方法也很简单，就是用不同的pattern去写尽可能所有的地址并读回比较。有一些常用的 pattern如0x5555, 0xAAAA等。10、几个简单的检测DDR故

5、障的方法上面的DDR检测算法，虽然全面，但是耗时比较长，常常需要好几个小时，在Uboot命令行下也有几个简单的命令可以检测常见内存故障，如下所示：1）、mtest addr lenth pattern这个命令需要注意，DDR在Uboot启动后被映射到了0地址，但是uboot的代码和堆、栈空间0x10000000处开始，这些空间是不能被刷的，否则就挂死了。2）、复制NOR flash的内容到内存中，如 cp.b 0x20080000 0x7fc0 20000，然后比较 cmp.b 0x20080000 0x7fc0 20000。3）、下载kernel image到内存中，copy NOR fla

6、sh 或tftp都行，然后调用iminfo LOAD_ADDR 检测CRC错误。第一种方法是用特定的pattern去刷DDR的空闲空间，第二种和第三种方法可以说Pattern的随机性更大一些。当然最彻底的检测方法当然是长时间跑Linux系统，上面的方法更适用于系统不稳定时定位错误。内存检测方法程序示例static void move64(unsigned long long *src, unsigned long long *dest)*dest = *src;/* This is 64 bit wide test patterns. Note that they reside in ROM*

7、 (which presumably works) and the tests write them to RAM which may* not work.* The otherpattern is written to drive the data bus to values other* than the test pattern. This is for detecting floating bus lines.*/const static unsigned long long pattern = 0xaaaaaaaaaaaaaaaaULL,0xccccccccccccccccULL,0

8、xf0f0f0f0f0f0f0f0ULL,0xff00ff00ff00ff00ULL,0xffff0000ffff0000ULL,0xffffffff00000000ULL,0x00000000ffffffffULL,0x0000ffff0000ffffULL,0x00ff00ff00ff00ffULL,0x0f0f0f0f0f0f0f0fULL,0x3333333333333333ULL,0x5555555555555555ULL;const unsigned long long otherpattern = 0x0123456789abcdefULL;/* 数据线检测 */static i

9、nt memory_post_dataline(unsigned long long * pmem)unsigned long long temp64 = 0;int num_patterns = sizeof(pattern)/ sizeof(pattern0);int i;unsigned int hi, lo, pathi, patlo;int ret = 0;for ( i = 0; i 32) & 0xffffffff;patlo = patterni & 0xffffffff;hi = (temp6432) & 0xffffffff;lo = temp64 & 0xffffffff

10、;post_log (Memory (date line) error at %08x, wrote %08x%08x, read %08x%08x !n,pmem, pathi, patlo, hi, lo);ret = -1;return ret;/* 地址线检测 */static int memory_post_addrline(ulong *testaddr, ulong *base, ulong size)ulong *target;ulong *end;ulong readback;ulong xor;int ret = 0;end = (ulong *)(ulong)base +

11、 size);/* pointer arith! */xor = 0;for(xor = sizeof(ulong); xor 0; xor = base) & (target end)/* 由于target是testaddr某一根地址线的值翻转得来 故testaddr != target,下面赋值操作后 应有*testaddr != *target */*testaddr = *target;readback = *target;#ifdef INJECT_ADDRESS_ERRORSif(xor = 0x00008000)readback = *testaddr;#endif /* 出现此

12、种情况只有testaddr = target,即某根地址线翻转无效 */if(readback = *testaddr)post_log (Memory (address line) error at %08x%08x, XOR value %08x !n,testaddr, target, xor);ret = -1;return ret;static int memory_post_test1 (unsigned long start, unsigned long size, unsigned long val)unsigned long i;ulong *mem = (ulong *)

13、start;ulong readback;int ret = 0;for (i = 0; i size / sizeof (ulong); i+) memi = val;if (i % 1024 = 0)WATCHDOG_RESET ();for (i = 0; i size / sizeof (ulong) & ret = 0; i+) readback = memi;if (readback != val) post_log (Memory error at %08x, wrote %08x, read %08x !n,mem + i, val, readback);ret = -1;br

14、eak;if (i % 1024 = 0)WATCHDOG_RESET ();return ret;static int memory_post_test2 (unsigned long start, unsigned long size)unsigned long i;ulong *mem = (ulong *) start;ulong readback;int ret = 0;for (i = 0; i size / sizeof (ulong); i+) memi = 1 (i % 32);if (i % 1024 = 0)WATCHDOG_RESET ();for (i = 0; i

15、size / sizeof (ulong) & ret = 0; i+) readback = memi;if (readback != (1 (i % 32) post_log (Memory error at %08x, wrote %08x, read %08x !n,mem + i, 1 (i % 32), readback);ret = -1;break;if (i % 1024 = 0)WATCHDOG_RESET ();return ret;static int memory_post_test3 (unsigned long start, unsigned long size)

16、unsigned long i;ulong *mem = (ulong *) start;ulong readback;int ret = 0;for (i = 0; i size / sizeof (ulong); i+) memi = i;if (i % 1024 = 0)WATCHDOG_RESET ();for (i = 0; i size / sizeof (ulong) & ret = 0; i+) readback = memi;if (readback != i) post_log (Memory error at %08x, wrote %08x, read %08x !n,

17、mem + i, i, readback);ret = -1;break;if (i % 1024 = 0)WATCHDOG_RESET ();return ret;static int memory_post_test4 (unsigned long start, unsigned long size)unsigned long i;ulong *mem = (ulong *) start;ulong readback;int ret = 0;for (i = 0; i size / sizeof (ulong); i+) memi = i;if (i % 1024 = 0)WATCHDOG

18、_RESET ();for (i = 0; i size / sizeof (ulong) & ret = 0; i+) readback = memi;if (readback != i) post_log (Memory error at %08x, wrote %08x, read %08x !n,mem + i, i, readback);ret = -1;break;if (i % 1024 = 0)WATCHDOG_RESET ();return ret;static int memory_post_tests (unsigned long start, unsigned long size)int ret = 0;if (ret = 0)ret = memory_post_dataline (unsigned long long *)start);WATCHDOG_RESET ();if (ret = 0)ret = memory_post_addrline (ulong *)start, (ulong *)start, size);WATCHDOG_RESET ();if (ret = 0)ret = m