nandtest error

Wed Apr 29 14:12:13 PDT 2015

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 at lists.infradead.org] On Behalf Of Han Xu
Sent: Wednesday, April 29, 2015 11:36 AM
To: Tee Zhen Cong
Cc: linux-mtd at lists.infradead.org
Subject: Re: nandtest error

On Wed, Apr 29, 2015 at 4:48 AM, Tee Zhen Cong <zc.tee at teraoka.com.sg> wrote:
> Hi all,
> I am using imx6SOLO to interface with a new 32Gb NAND flash from 
> MICRON, MT29F32G08CBADA.
> After applying the patch to truncate the remaining bytes out of the 
> power-of-2, imx6SOLO is able to detect and recognize the NAND flash.
> [    0.346874] ONFI flash detected
> [    0.347012] ONFI param page 0 valid
> [    0.347019] nand: onfi confirmed
>  [    0.347035] NAND device: Manufacturer ID: 0x2c, Chip ID: 0x44 (Micron
> MT29F32G08CBADAWP)
>  [    0.349811] Bad block table found at page 524032, version 0x01
>  [    0.352254] Bad block table found at page 523776, version 0x01
>  [    0.354979] Creating 3 MTD partitions on "gpmi-nand":
> [    0.354991] 0x000000000000-0x000000600000 : "kobs-ng"
> [    0.355750] 0x000000600000-0x000000a00000 : "kernel"
> [    0.356404] 0x000000a00000-0x000100000000 : "fs"
> [    0.357165] ---------------------------------------
> [    0.357173]        NFC Geometry (used by BCH)
> [    0.357179] ---------------------------------------
> [    0.357185] ECC Strength           : 56

The default ecc value beyond the the BCH capability(upto 40bit).
Please add  fsl,use-minimum-ecc = <1>; in dts nand portion.

> [    0.357190] Page Size in Bytes     : 8936
> [    0.357195] Metadata Size in Bytes : 10
> [    0.357200] ECC Chunk Size in Bytes: 1024
> [    0.357205] ECC Chunk Count        : 8
> [    0.357210] Payload Size in Bytes  : 8192
> [    0.357215] Auxiliary Size in Bytes: 20
> [    0.357220] Auxiliary Status Offset: 12
> [    0.357225] Block Mark Byte Offset : 7545
> [    0.357230] Block Mark Bit Offset  : 0
> [    0.357329] GPMI NAND driver registered. (IMX)
>
> However, when I tried to perform nandtest in my system, I always get 
> the error where some of the bytes read back is not the same as written in.
>> nandtest /dev/mtd2
> ECC corrections: 0
> ECC failures   : 0
> Bad blocks     : 6
> BBT blocks     : 0
> 00000000: checking...
> compare failed. seed 1667286349
> Byte 0x23ff is 4f should be 47
> Byte 0x882d is db should be d9
> Byte 0x1602a is 2f should be 2d
> Byte 0x39c1d is 8c should be 88
> Byte 0x66815 is 62 should be 60
> Byte 0x70833 is fb should be db
> Byte 0x7742b is 34 should be 35
> Byte 0x8601c is ab should be aa
> Byte 0x9c80a is b7 should be b3
> Byte 0xb141c is 59 should be 49
> Byte 0xc700f is c5 should be c7
> Byte 0xcc03c is de should be d6
> Byte 0xe1c02 is 3e should be 7e
> Byte 0xe6c13 is bc should be fc
> Byte 0xea016 is 67 should be 6f
> Byte 0xf0441 is 73 should be 72
> Byte 0xf4026 is 59 should be 58
> Byte 0xfc410 is 76 should be 56
> Byte 0x114c40 is c6 should be c4
> Byte 0x117c1e is 42 should be 40
> Byte 0x13c037 is ea should be e2
> Byte 0x151c08 is 74 should be 75
> Byte 0x16603b is 52 should be 50
> Byte 0x182824 is b7 should be b3
> Byte 0x187832 is 88 should be 89
> Byte 0x191c40 is 48 should be 40
> Byte 0x1b7002 is 47 should be c7
> Byte 0x1cf80c is 03 should be 01
> Byte 0x1d0c24 is 10 should be 90
> Byte 0x1d1c3b is 82 should be c2
> Byte 0x1ea83d is c7 should be 87
>
> It seems like for the bytes with error, there are always 1 bit errors, 
> and the bit location is random. If I tried to perform nandtest several 
> time, the address of the error bytes are different as well.
>
> I am using linux kernel version 3.0.35. Anybody has any idea why is 
> this happening? Is there any setting that I need to tweak to make it work?
> Thanks.
>
> Regards,
> zc
>
>
>
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