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

[Ivan Djelic]

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 ?

> We have been seeing mtd_oobtest failure on a partition size of 248 MB. Most of
> the time, test case 2 of mtd_oobtest is failing. On debugging further it seems
> that bit flip is happening on the test case 2 in OOB area. It is observed that
> the failure locations are consistent. 

If you are able to reproduce failures, then you should be able to tell which bits
in OOB are failing, by adding a few debugging lines in the code.

> To verify further we had tried writing zeros to OOB area and read it back. 
> This test is passing and confirms that all OOB bits (that are programmable)
> are not bad.

It does not confirm anything, bits can fail by remaining stuck at 0.

BR,
--
Ivan