[PATCH] ARM: OMAP3: gpmc: add BCH ecc api and modes

[Tony Lindgren]

* Tony Lindgren <tony at atomide.com> [120425 09:01]:
> * Artem Bityutskiy <dedekind1 at gmail.com> [120425 08:48]:
> > On Wed, 2012-04-25 at 08:23 -0700, Tony Lindgren wrote:
> > > Hi,
> > > 
> > > * Artem Bityutskiy <dedekind1 at gmail.com> [120425 07:52]:
> > > > On Tue, 2012-04-17 at 10:48 +0200, Ivan Djelic wrote:
> > > > > This patch adds a simple BCH ecc computation api, similar to the
> > > > > existing Hamming ecc api. It is intended to be used by the MTD layer.
> > > > > It implements the following features:
> > > > > 
> > > > > - support 4-bit and 8-bit ecc computation
> > > > > - do not protect user bytes in spare area, only data area is protected
> > > > > - ecc for an erased NAND page (0xFFs) is also a sequence of 0xFFs
> > > > > 
> > > > > This last feature is obtained by adding a constant polynomial to
> > > > > the hardware computed ecc. It allows to correct bitflips in blank pages
> > > > > and is extremely useful to support filesystems such as UBIFS, which expect
> > > > > erased pages to contain only 0xFFs.
> > > > > 
> > > > > This api has been tested on an OMAP3630 board.
> > > > > 
> > > > > Signed-off-by: Ivan Djelic <ivan.djelic at parrot.com>
> > > > 
> > > > Hi Tony,
> > > > 
> > > > what do you think about merging this patch? This is the enabler for
> > > > making UBIFS actually usable on OMAP platforms which use BCH ECC. There
> > > > are 2 other MTD patches which depend on this - so I wonder if it is
> > > > easier to merge this one via the MTD tree, providing it has your/others'
> > > > ack(s).
> > > 
> > > Looks OK to me, however there are other pending GPMC patches to convert
> > > it to a platform device device driver. Need to look those closer though.
> > > Anyways, it's best that I queue them to avoid merge conflicts.
> > 
> > Sure.
> > 
> > > Do you these for other changes for UBIFS?
> > 
> > Not in UBIFS, but in drivers/mtd/nand/omap2.c - Ivan sent another patch
> > which adds BCH support to to omap2.c, was sent to linux-omap, subject
> > "[PATCH] mtd: nand: omap: add support for hardware BCH ecc"
> > 
> > >  If so, I can set up an immutable
> > > branch for GPMC that you can merge in as well.
> > 
> > I guess this would be a good idea, but probably it is better to do this
> > when you believe you merged most gpmc patches, so probably closer to the
> > final -rc?
> 
> Yes let's wait a week or so as there are also the dmaengine patch for
> drivers/mtd/nand/omap2.c that might conflict. So let's get the dmaengine
> patches to some branch first.

Looking at the gpmc platform driver series, we can't merge those until
all the board-*.c files are converted. So let's plan on first making sure
the dmaengine changes work, then apply the BCH ecc patches.

Regards,

Tony