RE: nandtest error

Tee Zhen Cong
2015-04-30T01:29:22Z

Hi Jeff,
The flipped bits is found in the first 2Mbytes (1st block) of the NAND. It
stops at the first block where errors are detected. I am not so sure what is
happening in the nandtest application. It seems like a standard linux test
tool for nand where many ppl use. So I use it for my test as well.
As far as I see, it erase, write then read back the NAND block by block, and
see if the read back bytes are the same with the written bytes.
In my opinion, the flipped bits is not normal. I got another board with a
useable 16GBit NAND (MT29F16G08CBACA). Using the nandtest application, it
returns successful without any flipped bit. Same kernel, same software. Only
different NAND.

Regards,
zc

-----Original Message-----
From: linux-mtd [mailto:linux-mtd-bounces@lists.infradead.org] On Behalf Of
Jeff Lauruhn (jlauruhn)
Sent: Thursday, 30 April, 2015 5:12 AM
To: Han Xu; Tee Zhen Cong
Cc: linux-mtd@lists.infradead.org
Subject: RE: nandtest error

When you read the data back are you reading the raw data? Some amount of
bit flipping is normal NAND Flash behavior. ECC correction is required on
all contemporary NAND to some degree to correct bit flips. This Micron
device is designed to return a "FAIL" status only when the number of bad
bits in any page exceeds 40bits/1117 bytes.

I need to understand what nandtest is actually doing. If I read this right,
if found 32 flipped bits in a 32 gigabit device. That's actually very good.

Jeff Lauruhn
NAND Application Engineer
Embedded Business Unit
Micron Technology, Inc

-----Original Message-----
From: linux-mtd [mailto:linux-mtd-bounces@lists.infradead.org] On Behalf Of
Han Xu