[U-Boot] JFFS2 seems to drop nand data with ECC corrections

[Scott Wood <scottwood@freescale.com>]

On 12/01/2012 11:02:05 AM, Deltour, Stephane wrote:
> I had a few boards with NAND related problems. In Linux a file was
> written to a JFFS2 partition in NAND, but u-boot was unable to read  
> the
> same file correctly from the JFFS2. This happened to be often the case
> if the NAND had a few bad blocks in the JFFS2 partition.
> Upon further examination it turned out Linux still was able to read  
> the
> file 100% correctly from the partition, but u-boot wasn't.
> I did get a lot of "read_nand_cache: error reading nand off ..."
> messages in u-boot.
> 
> When debugging further it appears that
> read_nand_cached(...) in /fs/jffs2/jffs2_1pass.c
> throws away the data if nand_read (/drivers/ mtd/nand/nand_base.c)
> doesn't return 0.
> This happens in case of an uncorrectable ECC error (-EBADMSG) or a
> correctable ECC error(-EUCLEAN).
> (see nand_do_read_ops in /drivers/ mtd/nand/nand_base.c)
> 
> So this would mean that data gets thrown away in case of a correctable
> ECC error, which doesn't seem the right thing to do and probably does
> not match with how linux is behaving.
> 
> I patched the code to not throw away data with correctable ECC errors
> and this seems to fix it for the two boards that had this issue.
> If it matters: the correctable ECC errors appeared in good blocks (but
> often close to a bad block).
> 
> So would my understanding be 'correct'?

Yes.

-Scott