NAND ECC error in P1011

[hyoungkikim]

hi experts  

 I am afraid I can't express what I think in English well. But I hope you can understand it.

about  1 years ago  i designed a board based on P1020RDB  and it worked well  and made a few hundred boards 

i used a nand flash for u-boot and kernel/ramdisk and applications ( which was mounted as JFFS2)

recently  i got reports that  boards are not working   

i  checked a few board , and  the result  is that  data in nand flash are corrupted ( 1 or 2 bits in page)

in u-boot   i used nand dump command and compared with what is working 

if u-boot space was corrupted  a board isn't booting  ( u-boot and kernel/ramdisk is read-only in jffs2)

if kernel and ramdisk space was corrupted u-boot complains  crc checking error 

i wonder  that  nand flash data can be change  spontanously without access flash 

any tips and ideas are appreciated 

thank you in advance 

[Bulat]

Normally NAND flash data retention time should be greater than 1year of course, (depends on manufacturer). Constantly high tempterature of flash can also affect that time because it increases leakage from NAND flash cells.

If the same page of the flash is being erased/written very frequently, its endurance can be affected.

It is difficult to guess what is going on in your case. If this problem happened on many boards at the same time, it is quite possible that you have faced with low-grade batch of the NAND flash chips. Try to contact manufacturer of the memory, probably it is a known issue.

Regards,

Bulat