[PATCH v3 3/3] mtd-nand: DaVinci: Add 4-bit ECC support for large page NAND chips

[Narnakaje, Snehaprabha]

> -----Original Message-----
> From: Troy Kisky [mailto:troy.kisky at boundarydevices.com]
> Sent: Thursday, July 16, 2009 7:57 PM
> To: Narnakaje, Snehaprabha
> Cc: linux-mtd at lists.infradead.org; davinci-linux-open-
> source at linux.davincidsp.com; dwmw2 at infradead.org; tglx at linutronix.de;
> akpm at linux-foundation.org; Paulraj, Sandeep
> Subject: Re: [PATCH v3 3/3] mtd-nand: DaVinci: Add 4-bit ECC support for
> large page NAND chips
> 
> nsnehaprabha at ti.com wrote:
> > +/* An ECC layout for using 4-bit ECC with large-page (2048bytes) flash,
> > + * storing ten ECC bytes plus the manufacturer's bad block marker byte,
> > + * and not overlapping the default BBT markers.
> > + */
> > +static struct nand_ecclayout hwecc4_2048 __initconst = {
> > +	.eccbytes = 40,
> > +	.eccpos = {
> > +		/* at the end of spare sector */
> > +		24, 25, 26, 27, 28, 29,	30, 31, 32, 33,
> > +		34, 35, 36, 37, 38, 39,	40, 41, 42, 43,
> > +		44, 45, 46, 47, 48, 49, 50, 51, 52, 53,
> > +		54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
> > +		},
> > +	.oobfree = {
> > +		/* 1 byte at offset 0 holds manufacturer badblock marker */
> > +		{.offset = 1, .length = 23, },
> > +		/* 5 bytes at offset 8 hold BBT markers */
> > +		/* 8 bytes at offset 16 hold JFFS2 clean markers */
> > +	},
> > +};
> 
> I hate to sound like a broken record, but
> 
> If the bad block marker is only 1 byte. Don't you need to override
> 
> static struct nand_bbt_descr largepage_flashbased = {
> 	.options = NAND_BBT_SCAN2NDPAGE,
> 	.offs = 0,
> 	.len = 2,
> 	.pattern = scan_ff_pattern
> };
> 
> I think it is easier just to leave it as 2 bytes. That may
> allow substituting a different manufacturers chip too.

Yes, it is better to leave it as 2 bytes.

Thanks
Sneha
 
> 
>