To sum it up, my controller (iMX353) uses HW ECC by default, and I am
using MLC nand with 4k page and 218B oob.
My question is, is it at all possible to make this work with YAFFS using
oob tags (as opposed to inband-tags that work) or am I not in the right
direction.
YAFFS gives very good performance using the inband-tags option on our
device, the only issue is that the partition I am using it on is of
1.6GB size and when recovering from an unclean shutdown with the
partition having about 600MB on it, it takes 2:30 minutes to mount
and thats far too long.
So again, I apologize for asking this again and again but I haven't
found any information confirming/dis-confirming that I can make HW ECC
and oob
tags work on our MLC nand.
Thanks,
Boaz.
On Mon, 2011-01-17 at 23:50 +0200, Boaz Ben-David wrote:
> From looking at the ecclayout on mxc_nd2.c there are only 4 bytes in the oobfree member. How many bytes does yaffs need to store it's tags?
> Also, the imx35 uses hw ecc, I've read that mlc nand+hw ecc usually means one cannot really use the oob for anything else, is that true?
>
> Boaz Ben-David <boaz.bd@wellsense-tech.com> wrote:
>
>
> I'm using freescale's iMX353 and the nand is Samsung 2GB MLC 4k page with 218 bytes oob.
> I was somehow under the impression that writing to the oob area in MLC nand is problematic and thats why I tried using the inband tags option. Isn't it?
>
> Charles Manning <manningc2@actrix.gen.nz> wrote:
>
>
> On Friday 14 January 2011 10:59:03 Ross Younger wrote:
> > On 13/01/11 17:35, Boaz Ben-David wrote:
> > > Well, thanks for everyone for their support.
> > > It turns out that all I had to do is mount the partitions with the -o
> > > inband-tags flag for YAFFS2 to work correctly on my NAND.
> >
> > Good to hear you've got it working. However, inband tags reduce both the
> > storage capacity of the NAND[0] and the performance you can achieve[1].
> > I would recommend regular - out-of-band - tags if possible.
> >
> > [0] by the size of the packed tags struct (16 bytes) per page; about
> > 0.8% of a device with 2k pages.
> >
> > [1] in cases where YAFFS wants to read only the tags of a page, inband
> > mode has to read in the entire page and throw away all but the last 16
> > bytes. This adds up fast when mounting following an unclean shutdown,
> > when YAFFS has to scan the entire NAND.
>
> Yes, use out of band tags if you can. Inband tags will generally work even if
> the mtd driver's oob handling is broken so you're sidestepping the issue
> rather than fixing it.
>
> What NAND and NAND controller are you using?
>
> -- CHarles
>
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