[U-Boot] flash post test

[Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hi Scott,

Le 06/02/2012 23:55, Scott Wood a ?crit :
> On 02/06/2012 04:23 PM, Albert ARIBAUD wrote:
>> Hi Vaibhav,
>>
>> Le 06/02/2012 05:57, vaibhav kothari a ?crit :
>>> hi albert
>>>
>>> Yes,actually there is already support of flash test in POST of latest
>>> uboot.They are testing flash on every power on so am I for my board.But i
>>> don't want to disturb sectors in which uboot code relies. Can you help me
>>> here?
>>
>> I am no NAND specialist, but I do hope NAND POST tests are pure read
>> tests and thus are not affected by poweroffs (and can actually test any
>> part of NAND).
>
> NAND has a property called "read disturb", where excessively reading a
> sector without writing to it can eventually cause data loss.  U-Boot is
> already read once per boot, but reading it a second time could halve the
> expected lifetime.  Data managed by something like ubi is be scrubbed in
> a way that avoids this, but U-Boot itself is not usually managed in this
> way (boot hardware/rom does not understand ubi).

I *did* say I am not a NAND expert. :)

Thanks Scott. But then, isn't NAND testing a kind of catch-22, where by 
actually tesing if NAND works it one ends up weakening it either through 
read disturb, or simply through writes?

> -Scott

Amicalement,
-- 
Albert.