Dose linux-mtd really support mlc nand flash?

Dose linux-mtd really support mlc nand flash?

[liulunzuo]

Hi:
  Mlc nand flash should be write only once per write operation(NOP=1),
  but i found when i use mtd-utils to write a mtdchar device with oob ,
  it write a page twice: page and oob zone wrote separately,
  and mtdchar.c support no way to write a page and oob zone to the mlc
nand flash at the same time.

  And when a writing or eraseing operation fail, yaffs2 fs will mark
the block as bad block,
  but the function "markbad" will only write oob area neither use a
bad block scan first nor not.

  it seems a real problem when i use mlc nand flash under yaffs2.

  My English is so poor, could you know what i mean?

Thanks.

Best Regards!

Re: Dose linux-mtd really support mlc nand flash?

[Ricard Wanderlof]

On Sat, 23 Jan 2010, liulunzuo wrote:

>  Mlc nand flash should be write only once per write operation(NOP=1),
>  but i found when i use mtd-utils to write a mtdchar device with oob ,
>  it write a page twice: page and oob zone wrote separately,
>  and mtdchar.c support no way to write a page and oob zone to the mlc
> nand flash at the same time.

As far as I understand, mtd has not been used very much with MLC flash. 
There are some thoughts about using UBI on MLC 
(http://www.linux-mtd.infradead.org/faq/ubifs.html#L_why_ubiformat) but it 
seems it hasn't been tested to any extent. At any rate, UBI does not use 
the spare area in the flash for itself (like jffs2 does with cleanmarkers 
in empty blocks. Don't know how yaffs goes about its stuff).

>  And when a writing or eraseing operation fail, yaffs2 fs will mark
> the block as bad block,
>  but the function "markbad" will only write oob area neither use a
> bad block scan first nor not.

I'm not sure I understand you. markbad marks a block as being bad. It 
doesn't have to scan it first; it assumes whoever is calling it knows 
enough to make the proper decision.

yaffs (and yaffs2) are not really on-topic on this list, unless you mean 
jffs2.

/Ricard
-- 
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30

Re: Dose linux-mtd really support mlc nand flash?

[Artem Bityutskiy]

On Mon, 2010-01-25 at 09:53 +0100, Ricard Wanderlof wrote:
> On Sat, 23 Jan 2010, liulunzuo wrote:
> 
> >  Mlc nand flash should be write only once per write operation(NOP=1),
> >  but i found when i use mtd-utils to write a mtdchar device with oob ,
> >  it write a page twice: page and oob zone wrote separately,
> >  and mtdchar.c support no way to write a page and oob zone to the mlc
> > nand flash at the same time.
> 
> As far as I understand, mtd has not been used very much with MLC flash. 
> There are some thoughts about using UBI on MLC 
> (http://www.linux-mtd.infradead.org/faq/ubifs.html#L_why_ubiformat) but it 
> seems it hasn't been tested to any extent. At any rate, UBI does not use 
> the spare area in the flash for itself (like jffs2 does with cleanmarkers 
> in empty blocks. Don't know how yaffs goes about its stuff).

Yeah, a little better links for the MLC thoughts, though:

http://www.linux-mtd.infradead.org/faq/ubi.html#L_mlc
http://www.linux-mtd.infradead.org/faq/ubifs.html#L_ubifs_mlc

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)