[PATCH v2] mtd/nand : workaround for Freescale FCM to support large-page Nand chip

[Stijn Devriendt]

On Mon, Aug 15, 2011 at 6:11 PM, Scott Wood <scottwood at freescale.com> wrote:
> On 08/15/2011 10:59 AM, Artem Bityutskiy wrote:
>> On Tue, 2011-07-12 at 12:48 +0800, b35362 at freescale.com wrote:
>>> +    /*
>>> +     * Hack for supporting the flash chip whose writesize is
>>> +     * larger than 2K bytes.
>>> +     */
>>> +    if (mtd->writesize > 2048) {
>>> +            elbc_fcm_ctrl->subpage_shift = ffs(mtd->writesize >> 11) - 1;
>>> +            elbc_fcm_ctrl->subpage_mask =
>>> +                    (1 << elbc_fcm_ctrl->subpage_shift) - 1;
>>> +            /*
>>> +             * Rewrite mtd->writesize, mtd->oobsize, chip->page_shift
>>> +             * and chip->pagemask.
>>> +             */
>>> +            mtd->writesize = 2048;
>>> +            mtd->oobsize = 64;
>>> +            chip->page_shift = ffs(mtd->writesize) - 1;
>>> +            chip->pagemask = (chip->chipsize >> chip->page_shift) - 1;
>>> +    }
>>
>> So basically if the flash has 4KiB NAND pages, you are considering it as
>> a flash with 2KiB NAND pages. But surely this will work only if the
>> underlying flash has NOP 2 at least. Or even, if you consider that JFFS2
>> and YAFFS want to write to OOB, you need NOP 4 (2 ECC writes and 2
>> writes from YAFFS/JFFS2) ? So this won't work for NOP1 flashes?
>
> Right.  The set of chips that work with this controller is still larger
> with this than without this.
>
> It looks like NOP1 tends to be MLC -- you probably wouldn't want to use
> MLC with this controller anyway as it only does 1-bit ECC.
>
I currently have the fsl_elbc_nand driver working with BCH codes in software.
The patch is fairly small (although I'm just hardcoding the required ECC
configuration). I'll see if I can clean it up and push it upstream soon.

Regards,
Stijn