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SubjectRe: [PATCH 3/3] mtd/nand : workaround for Freescale FCM to support large-page Nand chip
On 12/06/2011 09:55 PM, LiuShuo wrote:
> 于 2011年12月07日 08:09, Scott Wood 写道:
>> On 12/03/2011 10:31 PM, shuo.liu@freescale.com wrote:
>>> From: Liu Shuo<shuo.liu@freescale.com>
>>>
>>> Freescale FCM controller has a 2K size limitation of buffer RAM. In
>>> order
>>> to support the Nand flash chip whose page size is larger than 2K bytes,
>>> we read/write 2k data repeatedly by issuing FIR_OP_RB/FIR_OP_WB and save
>>> them to a large buffer.
>>>
>>> Signed-off-by: Liu Shuo<shuo.liu@freescale.com>
>>> ---
>>> v3:
>>> -remove page_size of struct fsl_elbc_mtd.
>>> -do a oob write by NAND_CMD_RNDIN.
>>>
>>> drivers/mtd/nand/fsl_elbc_nand.c | 243
>>> ++++++++++++++++++++++++++++++++++----
>>> 1 files changed, 218 insertions(+), 25 deletions(-)
>> What is the plan for bad block marker migration?
> This patch has been ported to uboot now, I think we can make a special
> uboot image for bad
> block marker migration when first use the chip.

It should not be a special image, and there should be some way to mark
that the migration has happened. Even if we do the migration in U-Boot,
Linux could check for the marker and if absent, disallow access and tell
the user to run the migration tool.

>>> @@ -473,13 +568,72 @@ static void fsl_elbc_cmdfunc(struct mtd_info
>>> *mtd, unsigned int command,
>>> * write so the HW generates the ECC.
>>> */
>>> if (elbc_fcm_ctrl->oob || elbc_fcm_ctrl->column != 0 ||
>>> - elbc_fcm_ctrl->index != mtd->writesize + mtd->oobsize)
>>> - out_be32(&lbc->fbcr,
>>> - elbc_fcm_ctrl->index - elbc_fcm_ctrl->column);
>>> - else
>>> + elbc_fcm_ctrl->index != mtd->writesize + mtd->oobsize) {
>>> + if (elbc_fcm_ctrl->oob&& mtd->writesize> 2048) {
>>> + out_be32(&lbc->fbcr, 64);
>>> + } else {
>>> + out_be32(&lbc->fbcr, elbc_fcm_ctrl->index
>>> + - elbc_fcm_ctrl->column);
>>> + }
>> We need to limit ourselves to the regions that have actually been
>> written to in the buffer. fbcr needs to be set separately for first and
>> last subpages, with intermediate subpages having 0, 64, or 2112 as
>> appropriate. Subpages that are entirely before column or entirely after
>> column + index should be skipped.
>
> I have considered this case, but I don't think it is useful.
> 1.There isn't a 'length' parameter in driver interface, although we
> can get it from 'index - column'.

Right. column is start, and index is end + 1. We have the bounds of
what has been written.

> 2.To see nand_do_write_oob() in nand_base.c, it fill '0xff' to
> entire oob area first and write the user data by nand_fill_oob(), then
> call ecc.write_oob (default is nand_write_oob_std()).

Do we really want to assume that that's what it will always do?

And if we do want to make such assumptions, we could rip out all usage
of index/column here, and just handle "oob" and "full page" cases.

-Scott

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