OMAP3 NAND ECC selection

[Javier Martinez Canillas]

Hi Ezequiel,

On Thu, Dec 5, 2013 at 7:26 PM, Ezequiel Garcia
<ezequiel.garcia at free-electrons.com> wrote:
> Hi Javier,
>
> (CCing Brian: What do you think about this?)
>
> On Thu, Dec 05, 2013 at 06:39:10PM +0100, Javier Martinez Canillas wrote:
>> On Thu, Dec 5, 2013 at 6:13 PM, Tony Lindgren <tony at atomide.com> wrote:
>>
>> In the another thread [0] pointed out by Enric we were discussing the
>> same issue. Thomas suggested [1] that ideally we should be able to set
>> a per MTD partition ECC scheme. That way we can set 1 bit hamming for
>> the first MTD partition that has the SPL that the boot ROM needs to
>> read and the other partitions can use a more secure ECC scheme. I
>> completely agree with him.
>>
> [..]
>> global ECC scheme and we should expand the GPMC NAND DT binding so
>> partitions support the "ti,nand-ecc-opt". I'll see if I can get some
>> free time to try to implement that.
>>
>
> AFAIK, there's no hardware limitation that would prevent us from setting
> a per-partition ECC, keep in mind this effort is not reduced to make
> devicetree accept ECC on the partitions.
>

Agreed, in fact if you look at what I shared from the Micron NAND
datasheet used on IGEPv2 it says that different ECC schemes could be
used for block 0 and the rest of the NAND so definitely this is a
software limitation.

> While there are some per MTD device (which model each partition), the
> ECC mode is present in the, nand_chip structure. My understanding is that
> the NAND core hasn't been designed for this use case, and thus some
> major re-work is needed to accomplish it.
>

I see thanks for the clarification. I'm not familiar with the MTD
subsystem to be honest so I somehow misunderstood that other nand
drivers did this already and thought that it was just a matter of
adding support to the OMAP NAND driver.

> Therefore, it's a much short-term solution to implement the OMAP
> module parameter to fix the issue.
>
> Of course, feel free to prove me wrong :-)

Agreed.

> --
> Ezequiel García, Free Electrons
> Embedded Linux, Kernel and Android Engineering
> http://free-electrons.com

Thanks a lot and best regards,
Javier