linux-kernel - Re: [PATCH v6 00/17] memory: omap-gpmc: mtd: nand: Support GPMC NAND on non-OMAP platforms

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Date:	Mon, 18 Apr 2016 15:13:05 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Roger Quadros <rogerq@...com>
Cc:	Tony Lindgren <tony@...mide.com>, <javier@...hile0.org>,
	<fcooper@...com>, <nsekhar@...com>,
	<linux-mtd@...ts.infradead.org>, <linux-omap@...r.kernel.org>,
	<computersforpeace@...il.com>, <dwmw2@...radead.org>,
	<ezequiel@...guardiasur.com.ar>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 00/17] memory: omap-gpmc: mtd: nand: Support GPMC
 NAND on non-OMAP platforms

Hi Roger,

On Mon, 18 Apr 2016 15:52:58 +0300
Roger Quadros <rogerq@...com> wrote:

> On 18/04/16 15:31, Roger Quadros wrote:
> > On 16/04/16 11:57, Boris Brezillon wrote:
> >> On Fri, 15 Apr 2016 09:19:51 -0700
> >> Tony Lindgren <tony@...mide.com> wrote:
> >>
> >>>
> >>>> Or should I just pull this immutable branch in my current nand/next and
> >>>> let you pull the same immutable branch in omap-soc. I mean, would this
> >>>> prevent conflicts when our branches are merged into linux-next, no
> >>>> matter the order.
> >>>
> >>> Ideally just one or more branches with just minimal changes in
> >>> them against -rc1. But you may have other dependencies in
> >>> your NAND tree so that may no longer be doable :) Usually if
> >>> I merge something that may need to get merged into other
> >>> branches, I just apply them into a separate branch against -rc1
> >>> to start with, then merge that branch in.
> >>
> >> Okay, in this case, that's pretty much what I did from the beginning,
> >> except the immutable branch was provided by Roger (based on 4.6-rc1).
> >> Thanks for this detailed explanation, I'll try to remember that when
> >> I'll need to provide an immutable branch for another subsystem.
> >>
> >> Roger, my request remains, could you check/test my conflict resolution
> >> (branch nand/next-with-gpmc-rework)?
> > 
> > I couldn't test that branch yet as nand/next is broken on omap platforms
> > (at least on dra7-evm).
> > 
> > The commit where it breaks is:
> > a662ef4 mtd: nand: omap2: use mtd_ooblayout_xxx() helpers where appropriate
> > 
> > I'm trying to figure out what went wrong there. Failure log below.
> 
> OK. I was able to fix it when at commit a662ef4 with the below patch.

Thanks for debugging that.

> 
> Looks like we need to read exactly the ECC bytes through the ECC engine and not
> the entire OOB region.

Hm, it looks like there's a bug somewhere else, because I don't see any
reason why the controller wouldn't be able to read the full OOB region.

> 
> --cheers,
> -oger
> 
> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
> index e622a1b..46b61d2 100644
> --- a/drivers/mtd/nand/omap2.c
> +++ b/drivers/mtd/nand/omap2.c
> @@ -1547,8 +1547,8 @@ static int omap_read_page_bch(struct mtd_info *mtd, struct nand_chip *chip,
>  	chip->read_buf(mtd, buf, mtd->writesize);
>  
>  	/* Read oob bytes */
> -	chip->cmdfunc(mtd, NAND_CMD_RNDOUT, mtd->writesize, -1);
> -	chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
> +	chip->cmdfunc(mtd, NAND_CMD_RNDOUT, mtd->writesize + chip->ecc.layout->eccpos[0], -1);

The whole point of this series is to get rid of chip->ecc.layout, so
we'd rather use the mtd_ooblayout_find_eccregion() instead of
chip->ecc.layout->eccpos[0].

> +	chip->read_buf(mtd, chip->oob_poi, chip->ecc.total);

Can you print the ->oobsize, ->writesize, chip->ecc.layout->eccpos[0]
and chip->ecc.total values here. I'll also need your NAND page layout
(page size and OOB size provided in the datasheet).

Thanks,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com