From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S969574AbdDSVSI (ORCPT ); Wed, 19 Apr 2017 17:18:08 -0400 Received: from mail.free-electrons.com ([62.4.15.54]:56890 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967520AbdDSVSG (ORCPT ); Wed, 19 Apr 2017 17:18:06 -0400 Date: Wed, 19 Apr 2017 23:18:04 +0200 From: Boris Brezillon To: Pavel Machek 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? Message-ID: <20170419231804.5a04ed69@bbrezillon> In-Reply-To: <20170419121332.GA26979@amd> References: <20170419121332.GA26979@amd> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 19 Apr 2017 14:13:32 +0200 Pavel Machek 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