From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3AC05C43441 for ; Sun, 18 Nov 2018 19:43:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0D0D020817 for ; Sun, 18 Nov 2018 19:43:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0D0D020817 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726872AbeKSGEg (ORCPT ); Mon, 19 Nov 2018 01:04:36 -0500 Received: from mail.bootlin.com ([62.4.15.54]:57786 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725805AbeKSGEg (ORCPT ); Mon, 19 Nov 2018 01:04:36 -0500 Received: by mail.bootlin.com (Postfix, from userid 110) id A40D2207B0; Sun, 18 Nov 2018 20:43:25 +0100 (CET) Received: from bbrezillon (91-160-177-164.subs.proxad.net [91.160.177.164]) by mail.bootlin.com (Postfix) with ESMTPSA id 6045020510; Sun, 18 Nov 2018 20:43:25 +0100 (CET) Date: Sun, 18 Nov 2018 20:43:24 +0100 From: Boris Brezillon To: Naga Sureshkumar Relli Cc: "miquel.raynal@bootlin.com" , "richard@nod.at" , "dwmw2@infradead.org" , "computersforpeace@gmail.com" , "marek.vasut@gmail.com" , "linux-mtd@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "nagasuresh12@gmail.com" , "robh@kernel.org" , Michal Simek Subject: Re: [LINUX PATCH v12 3/3] mtd: rawnand: arasan: Add support for Arasan NAND Flash Controller Message-ID: <20181118204324.373ca9cc@bbrezillon> In-Reply-To: References: <1541739641-17789-1-git-send-email-naga.sureshkumar.relli@xilinx.com> <1541739641-17789-4-git-send-email-naga.sureshkumar.relli@xilinx.com> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 15 Nov 2018 09:34:16 +0000 Naga Sureshkumar Relli wrote: > Hi Boris & Miquel, > > I am updating the driver by addressing your comments, and I have one concern, especially in anfc_read_page_hwecc(), > there I am checking for erased pages bit flips. > Since Arasan NAND controller doesn't have multibit error detection beyond 24-bit( it can correct up to 24 bit), > i.e. there is no indication from controller to detect uncorrectable error beyond 24bit. Do you mean that you can't detect uncorrectable errors, or just that it's not 100% sure to detect errors above max_strength? > So I took some error count as default value(MULTI_BIT_ERR_CNT 16, I put this based on the error count that > I got while reading erased page on Micron device). > And during a page read, will just read the error count register and compare this value with the default error count(16) and if it is more > Than default then I am checking for erased page bit flips. Hm, that's wrong, especially if you set ecc_strength to something > 16. > I am doubting that this will not work in all cases. It definitely doesn't. > In my case it is just working because the error count that it got on an erased page is 16. > Could you please suggest a way to do detect erased_page bit flips when reading a page with HW-ECC?. I'm a bit lost. Is the problem only about bitflips in erase pages, or is it also impacting reads of written pages that lead to uncorrectable errors. Don't you have a bit (or several bits) reporting when the ECC engine was not able to correct data? I you do, you should base the "detect bitflips in erase pages" logic on this information.