Re: [Yaffs] about retiring a block

I agree with venu.
MLC can only be written once between 2 erase operation.
The second write to the same page can't promise the validity,
so the bad block marker can't be updated neither.

On Fri, Dec 16, 2011 at 12:15 PM, venu <bvg_1@yahoo.com> wrote:
>>> I prefer to not erase the block before writing the bad block marker. The
>>> rationale is that bad blocks might have various problems and the fewest
>>> possible writes should be performed on the block. Erasing the block
>>> might
>>> cause problems with marking the block.
>
> I'm of bit different opinion here. In case if you want to have
> same driver working for MLC and SLC nand flashes, then ideally
> you need to erase the block before writing anything on to it
> (including bad block marker).
>
> As MLCs do not allow multiple write operations on to the same
> page without erasing, you may lose the marker data itself in
> cases of marking without erase operation.
>
> Thanks,
> Venu
>
> ________________________________
> From: Charles Manning <manningc2@actrix.gen.nz>
> To: venu <bvg_1@yahoo.com>
> Sent: Friday, 16 December 2011 1:31 AM
> Subject: Re: [Yaffs] about retiring a block
>
> No that is not so.
>
> Bad block markers should be structured in a way that they can be marked
> without an erase. If the driver has some strange bad block marking strategy
> that requires erasure then it is up to the driver to perform the erasure as
> part of the bad block marking.
>
> Most Linux drivers reserve the first 2 oob bytes as a bad block marker and
> all
> that is needed is to write these to zero.
>
> I prefer to not erase the block before writing the bad block marker. The
> rationale is that bad blocks might have various problems and the fewest
> possible writes should be performed on the block. Erasing the block might
> cause problems with marking the block.
>
>
>
> On Thursday 15 December 2011 19:26:09 venu wrote:
>> Ideally erase operation should happen before marking block as BAD.
>> Without that we cannot ensure that the block will be really marked BAD.
>>
>>
>> ________________________________
>>  From: zheng shi <neversetsun@gmail.com>
>> To: YAFFS <yaffs@lists.aleph1.co.uk>
>> Cc: Charles Manning <manningc2@actrix.gen.nz>
>> Sent: Thursday, 15 December 2011 11:38 AM
>> Subject: [Yaffs] about retiring a block
>>
>> Hi,
>> I found it strange that there's no block erase operation before
>> calling yaffs_mark_bad.
>> But in mtd_utils/nandwrite.c, the block is erased before marking bad.
>>
>> Is it the expected behavior?
>>
>> Thanks!
>
>
>
>



--
Regards, Shizheng