[PATCH v4 1/5] mtd: nand: Detect Micron flash with on-die ECC (aka "internal ECC") enabled.

[David Mosberger-Tang]

Pekon,

On Wed, Apr 2, 2014 at 1:27 AM, Gupta, Pekon <pekon at ti.com> wrote:

> You have to consider multiple scenarios here (as Brian also suggested).
>
> (1) If a system does _not_ boot from NAND, instead it enables NAND
> only in kernel (like for rootfs). Then you need a mechanism to
> enable/disable on-die ECC in the kernel, the same way boot-loader does.

Why?  Like I said before, on-die ECC does not get turned on "accidentally".
Furthermore, it is always *safe* to use on-die ECC,  unlike the ECC provided
by the platform-specific drivers.

> (2) If a boot-loader, has enabled on-die ECC, but kernel driver supports
> even higher ECC scheme, then you need a hook in driver to allow user
> to 'disable' this feature.

Does that really happen in practice?

I'm much more worried about someone using too weak an ECC than wanting
to use a stronger than required ECC.  In fact, that's what got us
into this mess: we ended up using SWECC on a chip that required multi-bit
ECC (yes, shame on us that we didn't catch that, but stuff happens; obviously
we were not the only ones caught off-guard by this change).

  --david