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Date: Thu, 29 Mar 2012 18:28:14 +0200
From: Matthieu CASTET <matthieu.castet@parrot.com>
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To: Matteo Mattei <matteo.mattei@gmail.com>
Subject: Re: UBI/UBIFS issue: corrupt empty space => switched to read-only mode
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Hi,

Matteo Mattei a écrit :
> Artem Bityutskiy <dedekind1 <at> gmail.com> writes:
> 
>> On Fri, 2012-03-16 at 17:14 +0100, Matteo Mattei wrote:
>>> Hi guys,
>>>
>>> I am working hard on UBIFS to make it works on 2.6.32 and OMAP3530.
>>>
>>> I already posted some requests to TI forum but I have no answers up to now:
>>> http://e2e.ti.com/support/embedded/linux/f/354/t/171839.aspx#627875
>> Well, this error was reported several times. AFAIR, there are 2 possible
>> causes for this.
>>
>> 1. Your driver does not protect the empty space. Normally the driver
>> corrects bit-flips using ECC, but some systems do not do this for empty
>> space, i.e., for the flash regions which have been erased but have never
>> been written. UBIFS expects to see all 0xFFs there, and if it doesn't,
>> it reports about corrupt empty space.
>>
>> You can fix this by fixing the driver, at least this is what people seem
>> to do. If this is impossible to fix, you can teach UBIFS to tolerate
>> bit-flips in the empty space.
>>
>> 2. More difficult issue which no one still dares to start fixing is the
>> unstable bits issue. I do not have time to work on this, so I offer
>> everyone assistance, but no on so far started working on this, AFAIK.
>> Here is the description of the issue:
>>
>> http://www.linux-mtd.infradead.org/doc/ubifs.html#L_unstable_bits
>>
>> HTH.
>>
> 
> Hi Aartem,
> I have some updates (also a BCH fix) as reported here:
> http://e2e.ti.com/support/embedded/linux/f/354/t/171839.aspx
I recomend you to use the bch patch that ivan post some time ago on the ML for OMAP.

The TI one has some issues (and is slow).


Matthieu