[SOLVED] mtd read errors

dbrazeau · 11-05-2010, 02:12 PM

When I try to read from a mtd (NAND) device using dd I get errors when try to read 24000k or more.

Here are the dd commands I'm using:

Code:

dd if=/dev/mtd20 of=testimg_out bs=2048 count=11500
11500+0 records in
11500+0 records out

Code:

 dd if=/dev/mtd20 of=testimg_out bs=2048 count=12000
<3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable error :
 <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable error 
: <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable error
 : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable erro
r : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable err
or : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable er
ror : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable e
rror : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable error : <3>uncorrectable .......

Does anyone know what is wrong? Is there some kind of buffer size liming in the mtd driver?

dbrazeau · 11-05-2010, 04:33 PM

Looking at the bad block table it looks like the NAND partitions that I get read error on (which are ecc errors) are the partitions that contain bad blocks. The partitions that don't contain any bad blocks I do not get any read errors when reading them.

Is it possible that using dd to read/write to NAND does not skip the bad blocks?

dbrazeau · 11-05-2010, 06:28 PM

I install mtd-utils and used nandwrite to write to NAND and it work (it skips bad blocks). So in short dd is not a valid way to write to NAND because it doesn't skip the bad blocks as I suspected.