fsl_ifc_nand: are blank pages protected by ECC?

From	Pavel Machek <pavel@ucw.cz>
Newsgroups	linux.kernel
Subject	fsl_ifc_nand: are blank pages protected by ECC?
Date	2017-04-19 14:20 +0200
Message-ID	<txWKu-3m5-21@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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Hi!

We have some problems with fsl_ifc_nand ... in the old kernels, but
this one does not seem to be fixed in v4.11, either.

UBIFS complains:

UBIFS error (pid 931): ubifs_scan: corrupt empty space at LEB 282:252630
UBIFS error (pid 931): ubifs_scanned_corruption: corruption at LEB 282:252630
UBIFS error (pid 931): ubifs_scanned_corruption: first 1322 bytes from LEB 282:252630
UBIFS error (pid 931): ubifs_scan: LEB 282 scanning failed

Possible explanation is here:

https://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/289605

# I see on the forum that this issue has been raised before - my
# understanding is that the omap2 nand driver does not perform ECC
# detection/correction on empty pages so when UBIFS checks the empty
# space data and doesn't read all 0xFF then it fails and mounts
# read-only. I didn't find any good solution - only a workaround to
# remove the UBIFS check..

So I checked fsl_ifc_nand.c in v4.11-rc, and yes, it seems to have the
same problem:

			if (errors == 15) {
	                        /*
                                 * Uncorrectable error.
                                 * OK only if the whole page is blank.
                                 *
                                 * We disable ECCER reporting due to...
                                 * erratum IFC-A002770 -- so report it now if we
                                 * see an uncorrectable error in ECCSTAT.
                                 */
                                if (!is_blank(mtd, bufnum))
                                        ctrl->nand_stat |=
                                                IFC_NAND_EVTER_STAT_ECCER;
                                break;
                        }

is_blank() checks for all 0xff's, so single-bit 0xfe in the data will
result in_blank() == 0 and uncorrectable error being signaled.

Should the driver be modified somehow?

Thanks,
									Pavel

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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fsl_ifc_nand: are blank pages protected by ECC? Pavel Machek <pavel@ucw.cz> - 2017-04-19 14:20 +0200
  Re: fsl_ifc_nand: are blank pages protected by ECC? Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-04-19 23:20 +0200
    Re: fsl_ifc_nand: are blank pages protected by ECC? Pavel Machek <pavel@ucw.cz> - 2017-04-20 00:20 +0200
      Re: fsl_ifc_nand: are blank pages protected by ECC? Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-04-20 00:30 +0200
        Re: fsl_ifc_nand: are blank pages protected by ECC? Pavel Machek <pavel@ucw.cz> - 2017-04-20 13:50 +0200
          Re: fsl_ifc_nand: are blank pages protected by ECC? Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-04-20 14:20 +0200
          [PATCH] nand_base: optimize checking of erased buffers Pavel Machek <pavel@ucw.cz> - 2017-04-21 13:00 +0200
    Re: fsl_ifc_nand: are blank pages protected by ECC? Pavel Machek <pavel@ucw.cz> - 2017-04-21 12:10 +0200
      Re: fsl_ifc_nand: are blank pages protected by ECC? Richard Weinberger <richard@nod.at> - 2017-04-21 12:20 +0200
      Re: fsl_ifc_nand: are blank pages protected by ECC? Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-04-21 14:10 +0200
      Re: fsl_ifc_nand: are blank pages protected by ECC? Pavel Machek <pavel@ucw.cz> - 2017-04-21 15:40 +0200
        Re: fsl_ifc_nand: are blank pages protected by ECC? Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-04-21 15:50 +0200
          Re: fsl_ifc_nand: are blank pages protected by ECC? Pavel Machek <pavel@ucw.cz> - 2017-04-22 09:10 +0200
          [PATCH] tango_nand.c: fix ecc.stats_corrected in empty flash case Pavel Machek <pavel@ucw.cz> - 2017-04-22 12:50 +0200
          tango_nand: is logic right in error cases? (was Re: fsl_ifc_nand:  are blank pages protected by ECC?) Pavel Machek <pavel@ucw.cz> - 2017-04-23 12:00 +0200
            Re: tango_nand: is logic right in error cases? (was Re:  fsl_ifc_nand: are blank pages protected by ECC?) Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-04-24 09:20 +0200

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