目前，我使用的是am5728 custom hardware，在这里我遇到了一个nand问题。
u-boot的版本：2016.05-00319-g8d0b2ca-dirty
当我进行读写nand某些地址的时候，会得到一个错误提示“omap-elm: uncorrectable ECC errors”
nand芯片型号：MT29F4G08ABAEA（镁光）
u-boot 相关配置：
#define CONFIG_SYS_NAND_PAGE_SIZE 4096
#define CONFIG_SYS_NAND_OOBSIZE 224
#define CONFIG_SYS_NAND_BLOCK_SIZE (256*1024)
#define CONFIG_SYS_NAND_5_ADDR_CYCLE
#define CONFIG_SYS_NAND_PAGE_COUNT (CONFIG_SYS_NAND_BLOCK_SIZE / \
CONFIG_SYS_NAND_PAGE_SIZE)
#define CONFIG_NAND_OMAP_GPMC
#define CONFIG_NAND_OMAP_GPMC_PREFETCH
#define CONFIG_NAND_OMAP_ELM
#define CONFIG_SYS_NAND_ONFI_DETECTION
#define CONFIG_SYS_NAND_BAD_BLOCK_POS NAND_LARGE_BADBLOCK_POS
#define CONFIG_NAND_OMAP_ECCSCHEME \
OMAP_ECC_BCH16_CODE_HW
#define CONFIG_SYS_NAND_ECCBYTES 26
#define CONFIG_SYS_NAND_ECCSIZE 512
#define CONFIG_SYS_NAND_ECCPOS { 2, 3, 4, 5, 6, 7, 8, 9, \
10, 11, 12, 13, 14, 15, 16, 17, 18, 19, \
20, 21, 22, 23, 24, 25, 26, 27, 28, 29, \
30, 31, 32, 33, 34, 35, 36, 37, 38, 39, \
40, 41, 42, 43, 44, 45, 46, 47, 48, 49, \
50, 51, 52, 53, 54, 55, 56, 57, 58, 59, \
60, 61, 62, 63, 64, 65, 66, 67, 68, 69, \
70, 71, 72, 73, 74, 75, 76, 77, 78, 79, \
80, 81, 82, 83, 84, 85, 86, 87, 88, 89, \
90, 91, 92, 93, 94, 95, 96, 97, 98, 99, \
100, 101, 102, 103, 104, 105, 106, 107, 108, 109, \
110, 111, 112, 113, 114, 115, 116, 117, 118, 119, \
120, 121, 122, 123, 124, 125, 126, 127, 128, 129, \
130, 131, 132, 133, 134, 135, 136, 137, 138, 139, \
140, 141, 142, 143, 144, 145, 146, 147, 148, 149, \
150, 151, 152, 153, 154, 155, 156, 157, 158, 159, \
160, 161, 162, 163, 164, 165, 166, 167, 168, 169, \
170, 171, 172, 173, 174, 175, 176, 177, 178, 179, \
180, 181, 182, 183, 184, 185, 186, 187, 188, 189, \
190, 191, 192, 193, 194, 195, 196, 197, 198, 199, \
200, 201, 202, 203, 204, 205, 206, 207, 208, 209, }
我没有使用nand启动的方式，而是uart启动，启动之后对nand进行读写，nand的大部分区域读写是成功的，
错误提示：
=> nand read 8200000 6b0000 1000
NAND read: device 0 offset 0x6b0000, size 0x1000
4096 bytes read: OK
=> nand read 8200000 6b0000 10000
NAND read: device 0 offset 0x6b0000, size 0x10000
65536 bytes read: OK
=> nand read 8200000 6c0000 1000
NAND read: device 0 offset 0x6c0000, size 0x1000
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
NAND read from offset 6c0000 failed -74
0 bytes read: ERROR
=>
不只有这一个地址是不可读的，有很多这样的“坏块”，但是只要对这个地址进行写操作之后，这个地址就有变成“好块”了
=> nand read 8200000 6c0000 1000
NAND read: device 0 offset 0x6c0000, size 0x1000 这里是不能够读的
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
omap-elm: uncorrectable ECC errors
NAND read from offset 6c0000 failed -74
0 bytes read: ERROR
=> nand erase 6c0000 1000
NAND erase: device 0 offset 0x6c0000, size 0x1000
Erasing at 0x6c0000 -- 100% complete.
OK
=> nand read 8200000 6c0000 1000
NAND read: device 0 offset 0x6c0000, size 0x1000 这里读取成功了
4096 bytes read: OK
=>
这个到底是哪里出现问题了呢？
