[PATCH 2.6.30-rc6 3/3] NAND: Add 4-bit ECC support for large page NAND chips

[Narnakaje, Snehaprabha]

Troy,

> -----Original Message-----
> From: Troy Kisky [mailto:troy.kisky at boundarydevices.com]
> Sent: Monday, May 18, 2009 8:17 PM
> To: Narnakaje, Snehaprabha
> Cc: dwmw2 at infradead.org; davinci-linux-open-source at linux.davincidsp.com;
> linux-mtd at lists.infradead.org; tglx at linutronix.de; akpm at linux-
> foundation.org
> Subject: Re: [PATCH 2.6.30-rc6 3/3] NAND: Add 4-bit ECC support for large
> page NAND chips
> 
> Troy Kisky wrote:
> > nsnehaprabha at ti.com wrote:
> >> From: Sneha Narnakaje <nsnehaprabha at ti.com>
> >>
> >> This patch adds 4-bit ECC support for large page NAND chips using the
> new ECC
> >> mode NAND_ECC_HW_OOB_FIRST. The platform data from board-dm355-evm has
> been
> >> adjusted to use this mode.
> >>
> >> The patches have been verified on DM355 device with 2K Micron devices
> using
> >> mtd-tests and JFFS2. Error correction upto 4-bits has also been
> verified using
> >> nandwrite/nanddump utilities.
> >>
> >> Reviewed-by: David Brownell <dbrownell at users.sourceforge.net>
> >> Signed-off-by: Sneha Narnakaje <nsnehaprabha at ti.com>
> >> ---
> >>  drivers/mtd/nand/davinci_nand.c |   37
> +++++++++++++++++++++++++++++++------
> >>  1 files changed, 31 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/mtd/nand/davinci_nand.c
> b/drivers/mtd/nand/davinci_nand.c
> >> index ba6940d..4557b8d 100644
> >> --- a/drivers/mtd/nand/davinci_nand.c
> >> +++ b/drivers/mtd/nand/davinci_nand.c
> >> @@ -689,15 +707,22 @@ static int __init nand_davinci_probe(struct
> platform_device *pdev)
> >>  				info->mtd.oobsize - 16;
> >>  			goto syndrome_done;
> >>  		}
> >> +		if (chunks == 4) {
> >> +			info->ecclayout = hwecc4_2048;
> >> +			info->ecclayout.oobfree[1].length =
> >> +				info->mtd.oobsize - 49;
> >
> Most drivers set chip->ecc.layout = ... Is it ok to use ecclayout
> instead?????

info->ecclayout is internal to davinci nand driver, since info is of type 'struct davinci_nand_info'.

In the davinci_nand.c source, there is already code to assign info->ecclayout to chip->ecc.layout.

syndrome_done:
                info->chip.ecc.layout = &info->ecclayout;

We have this internal structure to handle different ecc modes (ecc bits vs. page sizes).

Thanks
Sneha

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