u-boot nand flash read/write debug(2018-08-01)

原创已于 2024-01-08 22:03:16 修改 · 1.5k 阅读

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于 2018-08-04 22:22:24 首次发布

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本文详细记录了解决NAND Flash读写错误的过程，包括分析读写操作的代码流程，发现并修正ECC校验配置错误，最终实现稳定的数据读写。

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nand read 30000000 0 10000

NAND read: device 0 offset 0x0, size 0x10000
entry nand_read=mtd_read
entry mtd_read and call mtd->_read
entry nand_read
entry nand_do_read_ops
need_skip = 0
NAND read from offset 0 failed -74
0 bytes read: ERROR
出错代码位置：
if (!need_skip) {
       rval = nand_read(nand, offset, length, buffer);
       if (!rval || rval == -EUCLEAN)
           return 0;

       *length = 0;
       printf("NAND read from offset %llx failed %d\n",
           offset, rval);
       return rval;
   }
一个设置项：nand->ecc.mode = NAND_ECC_SOFT;
所影响的代码：
case NAND_ECC_SOFT:
       ecc->calculate = nand_calculate_ecc;
       ecc->correct = nand_correct_data;
       ecc->read_page = nand_read_page_swecc;
       ecc->read_subpage = nand_read_subpage;
       ecc->write_page = nand_write_page_swecc;
       ecc->read_page_raw = nand_read_page_raw;/********/
       ecc->write_page_raw = nand_write_page_raw;
       ecc->read_oob = nand_read_oob_std;
       ecc->write_oob = nand_write_oob_std;
       if (!ecc->size)
           ecc->size = 256;
       ecc->bytes = 3;
       ecc->strength = 1;
       break;
case NAND_ECC_NONE:
       pr_warn("NAND_ECC_NONE selected by board driver. This is not recommended!\n");
       ecc->read_page = nand_read_page_raw;
       ecc->write_page = nand_write_page_raw;
       ecc->read_oob = nand_read_oob_std;
       ecc->read_page_raw = nand_read_page_raw;
       ecc->write_page_raw = nand_write_page_raw;
       ecc->write_oob = nand_write_oob_std;
       ecc->size = mtd->writesize;
       ecc->bytes = 0;
       ecc->strength = 0;
       break;
读失败可能是没加片选操作chip->select_chip(mtd, 0);
片选命令不需要再加了，在读命令发出前，前段代码有发送片选命令

现在的问题是可以正确读出nandflash中的数据，但是总是提示读错误，不知为何！

终于找到原因了：
是ecc校验有问题，u-boot中默认支持的ecc页大小与我的板子上的不符合，具体如下

   /*
   * Check ECC mode, default to software if 3byte/512byte hardware ECC is
   * selected and we have 256 byte pagesize fallback to software ECC
   */
..nand_scant_tail:
   switch (ecc->mode) {...}位于nand_base.c中

在此语句上添加ecc->mode=NAND_ECC_NONE，即使用ecc校验，重新编译下载后，完美成功。
测试结果：其中读结束返回的大小为bytes字节，而cmp返回的是字数words，即4个字节
u-boot-2015.10 # nand read 30080000 0 80000

NAND read: device 0 offset 0x0, size 0x80000
entry nand_read=mtd_read
entry mtd_read and call mtd->_read
entry nand_read
entry nand_do_read_ops
oob=0,ret=0,ecc_fail=0,max_bitflips=0
nand_read return value=0
mtd_read:ret_code=0,ecc_strength=0
need_skip = 0,rval=0
524288 bytes read: OK
u-boot-2015.10 # nand read 30000000 0 80000

NAND write: device 0 offset 0xfffff00, size 0x100
Attempt to write non page-aligned data
0 bytes written: ERROR

u-boot-2015.10 # nand write 30000000 f000000 800

NAND write: device 0 offset 0xf000000, size 0x800
entry nand_read=mtd_read
entry mtd_read and call mtd->_read
entry nand_read
entry nand_do_read_ops
oob=0,ret=0,ecc_fail=0,max_bitflips=0
nand_read return value=0
mtd_read:ret_code=0,ecc_strength=0
NAND write to offset f000000 failed -5
0 bytes written: ERROR
从下面的输出并结合代码可以看出：之所以会出现读操作，并不是刚开始认为的写操作函数变成了
读操作函数，而是写操作中有数据校验这个功能，所以需要重新读出数据进行对比，因此有了读操作
的信息输出。
Flash: 2 MiB
NAND: set mtd->_read = nand_read<872222912>
set mtd->_write = nand_write<872219876>
256 MiB

u-boot-2015.10 # nand write 30100000 f000000 800

NAND write: device 0 offset 0xf000000, size 0x800
entry mtd_write and call mtd->_write
entry nand_read=mtd_read
entry mtd_read and call mtd->_read
entry nand_read
entry nand_do_read_ops
oob=0,ret=0,ecc_fail=0,max_bitflips=0
nand_read return value=0
mtd_read:ret_code=0,ecc_strength=0
NAND write to offset f000000 failed -5
0 bytes written: ERROR
现在可以确定了确实是写函数有问题了。
   if (!chip->read_byte || chip->read_byte == nand_read_byte)
       chip->read_byte = busw ? nand_read_byte16 : nand_read_byte;
   if (!chip->read_word)
       chip->read_word = nand_read_word;
   if (!chip->block_bad)
       chip->block_bad = nand_block_bad;
   if (!chip->block_markbad)
       chip->block_markbad = nand_default_block_markbad;
   if (!chip->write_buf || chip->write_buf == nand_write_buf)
       chip->write_buf = busw ? nand_write_buf16 : nand_write_buf;
   if (!chip->write_byte || chip->write_byte == nand_write_byte)
       chip->write_byte = busw ? nand_write_byte16 : nand_write_byte;
   if (!chip->read_buf || chip->read_buf == nand_read_buf)
       chip->read_buf = busw ? nand_read_buf16 : nand_read_buf;
写操作技术路线：
chip->write_page = nand_write_page;
   |->if (unlikely(raw))
       status = chip->ecc.write_page_raw(mtd, chip, buf,oob_required);
目前看没有什么问题，可是没有发现发送写命令的操作！
通过查看代码，基本可以确定，确实没有发送写命令。
include/linux/mtd/nand.h:#define NAND_CMD_SEQIN       0x80
找到了，源代码是有发送写命令的，看来问题还在别处：
   chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);
   if (unlikely(raw))
       status = chip->ecc.write_page_raw(mtd, chip, buf,
                           oob_required);
对比1.1.6的代码，和2015.10的还是有一些差别的