[U-Boot] [PATCH 1/3] mtd: driver _read() returns max_bitflips; mtd_read() returns -EUCLEAN

[Scott Wood]

On Mon, 2013-08-19 at 10:55 +0200, Stefan Roese wrote:
> On 06.08.2013 12:13, Paul Burton wrote:
> > Linux modified the MTD driver interface in commit edbc4540 (with the
> > same name as this commit). The effect is that calls to mtd_read will not
> > return -EUCLEAN if the number of ECC-corrected bit errors is below a
> > certain threshold, which defaults to the strength of the ECC. This
> > allows -EUCLEAN to stop indicating "some bits were corrected" and begin
> > indicating "a large number of bits were corrected, the data held in this
> > region of flash may be lost soon". UBI makes use of this and when
> > -EUCLEAN is returned from mtd_read it will move data to another block of
> > flash. Without adopting this interface change UBI on U-boot attempts to
> > move data between blocks every time a single bit is corrected using the
> > ECC, which is a very common occurance on some devices. For some devices
> > it can be so common that UBI gets stuck constantly moving data around
> > because each block it attempts to use has a single bit error.  This
> > patch adopts the interface change as in Linux commit edbc4540 in order
> > to avoid such situations.
> > 
> > Given that none of the drivers under drivers/mtd return -EUCLEAN, this
> > should only affect those using software ECC. I have tested that it works
> > on a board which is currently out of tree, but which I hope to be able
> > to begin upstreaming soon.
> 
> Paul, a quick question to clarify this. This patch fixes a regression in
> the current mtd->_read implementation (used by UBI) that was introduced
> by the MTD sync to v3.7.1? Is this correct?
> 
> And what error exactly did occur on your system?