tango_nand: is logic right in error cases? (was Re: fsl_ifc_nand: are blank pages protected by ECC?)

Pavel Machek
2017-04-23T09:58:58Z

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Hi!

> > Maybe I figured it out. Unfortunately, it is only compile tested. Does
> > it look approximately right?
>
> Yep that's definitely better. Just one thing missing (see below),
> otherwise it looks good.

I'm copying from tango_nand, therefore I had to check tango_nand, too.

static int check_erased_page(struct nand_chip *chip, u8 *buf)
{
...
res = nand_check_erased_ecc_chunk(buf, pkt_size, ecc, ecc_size,
meta, meta_len,
chip->ecc.strength);
if (res < 0)
mtd->ecc_stats.failed++;
else
mtd->ecc_stats.corrected += res;

bitflips = max(res, bitflips);
...
return bitflips;
}

static int tango_read_page(struct mtd_info *mtd, struct nand_chip *chip,
u8 *buf, int oob_required, int page)
{
...
res = decode_error_report(nfc);
if (res < 0) {
chip->ecc.read_oob_raw(mtd, chip, page);
res = check_erased_page(chip, buf);
}

return res;
}

So nand_check_erased_ecc_chunk() returns < 0 (failed ECC), but then we
perform max() with bitflips (lets say 1, correctable ECC) and return
1? tango_read_page then returns 1 (correctable ECC) forgetting about
failed ECC...?

Best regards,
Pavel