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From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: richard@nod.at, dwmw2@infradead.org, computersforpeace@gmail.com,
	marek.vasut@gmail.com, cyrille.pitchen@atmel.com,
	linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
	mark.marshall@omicronenergy.com, b44839@freescale.com,
	prabhakar@freescale.com
Subject: Re: fsl_ifc_nand: are blank pages protected by ECC?
Date: Wed, 19 Apr 2017 23:18:04 +0200	[thread overview]
Message-ID: <20170419231804.5a04ed69@bbrezillon> (raw)
In-Reply-To: <20170419121332.GA26979@amd>

On Wed, 19 Apr 2017 14:13:32 +0200
Pavel Machek <pavel@ucw.cz> wrote:

> 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?

Yep, nand_check_erased_ecc_chunk() [1] is here to help you check this
case, unfortunately, it's not directly applicable here, because this
function takes regular pointers and not __iomem ones. You'll either
have to copy the data in an intermediate buffer before calling
nand_check_erased_ecc_chunk(), or cast the SRAM region to a void
pointer (which is usually not a good idea). The last option would be to
open code nand_check_erased_ecc_chunk(), but I'd really like to avoid
that (for maintainability concerns).

[1]http://lxr.free-electrons.com/source/drivers/mtd/nand/nand_base.c#L1414

  reply	other threads:[~2017-04-19 21:18 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-19 12:13 fsl_ifc_nand: are blank pages protected by ECC? Pavel Machek
2017-04-19 21:18 ` Boris Brezillon [this message]
2017-04-19 22:15   ` Pavel Machek
2017-04-19 22:27     ` Boris Brezillon
2017-04-20 11:40       ` Pavel Machek
2017-04-20 12:15         ` Boris Brezillon
2017-04-21 10:51         ` [PATCH] nand_base: optimize checking of erased buffers Pavel Machek
2017-05-17 11:27           ` Mason
2017-05-17 11:39             ` Mason
2017-05-17 11:52             ` Pavel Machek
2017-05-17 12:22           ` [PATCH] fsl_ifc_nand: fix handing of bit flips in erased nand Pavel Machek
2017-05-17 12:32             ` Boris Brezillon
2017-05-17 13:00               ` Pavel Machek
2017-05-17 13:25                 ` Boris Brezillon
2017-05-17 20:03                   ` [PATCH] mtd: nand: fsl_ifc: fix handing of bit flips in erased pages Pavel Machek
2017-05-31 20:59                     ` [PATCHv2] " Pavel Machek
2017-05-31 22:59                       ` Darwin Dingel
2017-06-01  1:09                       ` Darwin Dingel
2017-06-01 13:12                         ` Pavel Machek
2017-06-01 13:21                           ` Boris Brezillon
2017-06-07  7:31                             ` Boris Brezillon
2017-04-21 10:08   ` fsl_ifc_nand: are blank pages protected by ECC? Pavel Machek
2017-04-21 10:12     ` Richard Weinberger
2017-04-21 12:04     ` Boris Brezillon
2017-04-21 13:37     ` Pavel Machek
2017-04-21 13:49       ` Boris Brezillon
2017-04-22  7:01         ` Pavel Machek
2017-04-22 10:40         ` [PATCH] tango_nand.c: fix ecc.stats_corrected in empty flash case Pavel Machek
2017-04-23  9:58         ` tango_nand: is logic right in error cases? (was Re: fsl_ifc_nand: are blank pages protected by ECC?) Pavel Machek
2017-04-24  7:12           ` Boris Brezillon

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