[U-Boot] [PATCH 2/2] MTD:NAND: ADD new ECC mode NAND_ECC_HW_OOB_FIRST

[Paulraj, Sandeep]

> John Rigby wrote:
> > Sorry for the late comments.  We have been trying to use this code with
> > the associated davinci 4-bit ecc patches and have some questions
We use this internally and it works. Are you having any issues because we don't see any!!
J-C has to apply a patch and you will need that for this to work properly.
That patch updates the DM355 Config
> (inline).
> >
> >     .....
> >     +       uint8_t *ecc_code = chip->buffers->ecccode;
> >     +       uint32_t *eccpos = chip->ecc.layout->eccpos;
> >     +       uint8_t *ecc_calc = chip->buffers->ecccalc;
> >     +
> >     +       /* Read the OOB area first */
> >     +       chip->cmdfunc(mtd, NAND_CMD_READOOB, 0, page);
> >
> >
> > What about chips that do not support the  NAND_CMD_READOOB?  Do I need
> > to provide my own read routine for that case?
> 
> cmdfunc is supposed to fix that up.  This is already the case with
> existing code.
> 
> >     +       chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
> >     +       chip->cmdfunc(mtd, NAND_CMD_READ0, 0, page);
> >     +
> >     +       for (i = 0; i < chip->ecc.total; i++)
> >     +               ecc_code[i] = chip->oob_poi[eccpos[i]];
> >     +
> >     +       for (i = 0; eccsteps; eccsteps--, i += eccbytes, p +=
> eccsize) {
> >     +               int stat;
> >     +
> >     +               chip->ecc.hwctl(mtd, NAND_ECC_READ);
> >     +               chip->read_buf(mtd, p, eccsize);
> >     +               chip->ecc.calculate(mtd, p, &ecc_calc[i]);
> >
> >
> > Here you calculate ecc then never use the result?
> 
> Hmm, that looks wrong, both here and in the davinci driver.  Are the two
> calls to nand_davinci_4bit_readecc reading different things?  Does the
> calculate function have any side effects beyond producing data that is
> never used?
Have you reads the patch description. Maybe that might help a bit

This patch adds the new mode NAND_ECC_HW_OOB_FIRST in the nand code to
support 4-bit ECC on TI DaVinci devices with large page (up to 2K) NAND
chips.  This ECC mode is similar to NAND_ECC_HW, with the exception of
read_page API that first reads the OOB area, reads the data in chunks,
feeds the ECC from OOB area to the ECC hw engine and perform any
correction on the data as per the ECC status reported by the engine.

> 
> -Scott
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