Re: [PATCH] mtd: nand: Add support for reading ooblayout from device tree

From: Paul Cercueil
Date: Sat May 12 2018 - 10:38:57 EST

Le sam. 12 mai 2018 à 10:42, Boris Brezillon <boris.brezillon@xxxxxxxxxxx> a écrit :
On Sat, 12 May 2018 08:55:40 -0300
Paul Cercueil <paul@xxxxxxxxxxxxxxx> wrote:

Hi Boris,

Le 12 mai 2018 02:55, Boris Brezillon <boris.brezillon@xxxxxxxxxxx> a écrit :
> Hi Paul,
> On Fri, 11 May 2018 23:29:12 +0200
> Paul Cercueil <paul@xxxxxxxxxxxxxxx> wrote:
> > By specifying the properties "mtd-oob-ecc" and "mtd-oob-free", it is
> > now possible to specify from devicetree where the ECC data is located
> > inside the OOB region.
> Why would we want to do that? I mean, ECC/free regions are ECC
> controller dependent (and NAND chip dependent for the OOB size part),
> so there's no reason to describe it in the DT. And more importantly,
> people are likely to get it wrong.
> I'm curious, why do you need that?

Good question.

The reason is that some SoCs have no ECC controller.
The various boards for these SoCs then all use a different layout.

Okay. Still think defining the layouts in the DT is a bad idea. We
can add a jz4740 specific property to define the layout id
(ingenic,nand-oob-layout = <layout-id>), but not a generic way to
define custom layouts for all kind of NAND controller.


My motivation is to get rid of this (move it to devicetree):
And enable the support of other boards with custom OOB layouts.

Can you list the different layouts you have? I'm pretty sure there's a
pattern. Maybe we can even deduce the layout from the page size or OOB

This is the other layout I have for another ingenic device:

Page size and OOB size are the same between these two devices.