mtd oob test is failing consistently at same places in NAND flash

[Philip, Avinash]

On Wed, May 09, 2012 at 00:15:16, Ivan Djelic wrote:
> On Tue, May 08, 2012 at 04:09:46PM +0100, Philip, Avinash wrote:
> > On Tue, May 08, 2012 at 18:53:54, Ivan Djelic wrote:
> > > On Tue, May 08, 2012 at 01:33:06PM +0100, Philip, Avinash wrote:
> > > > Hi,
> > > > 
> > > > We are having an 8-bit NAND part (MT29F2G08ABAEAWP from Micron) 
> > > > connected to GPMC Module (General purpose memory controller) from TI.
> > > 
> > > Hi,
> > > How is ecc performed ?
> > > Using NAND internal ecc ? or with GPMC 1-bit Hamming ? 4-bit/8-bit BCH ?
> > > Which version of omap2 driver are you using ?
> > > Is OOB also ECC-protected ?
> > 
> > Hardware ECC is performing.
> > 4-bit BCH ECC scheme is used.
> > I am using omap2 driver in Linux 3.2.0 Kernel. Don't know omap2 driver version.
> 
> You are probably using a patched kernel, since 3.2.0 does not have GPMC BCH support ?!
> What is your ecc layout ? Does it expose oobfree regions ?
>

Yes, we had using patched kernel. OOB free region is exposed.

ECC layout will be as follows.

0-1	-> BAD block marking
2-57  -> ECC byte position, ( 14 bytes for 512 byte)
58-63 -> oob free bytes

mtd->ecclayout->eccbytes		= 56
mtd->ecclayout->eccpos[0]	= 2
mtd->ecclayout->oobavail		= 6
mtd->ecclayout->oobfree[0].offset	= 58
mtd->ecclayout->oobfree[0].length	= 6

Regards
Avinash

> > No, OOB is not ECC protected.
> 
> Well, in that case, isn't it normal that mtd_oobtest should fail if there happens to be a single bitflip in the available OOB area ? (of size mtd->ecclayout->oobavail for each page)
>
> BR,
> --
> Ivan
>