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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 8903AC4321E for ; Fri, 7 Sep 2018 14:08:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E6AF2083D for ; Fri, 7 Sep 2018 14:08:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E6AF2083D 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 S1728875AbeIGStm (ORCPT ); Fri, 7 Sep 2018 14:49:42 -0400 Received: from mail.bootlin.com ([62.4.15.54]:43796 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726594AbeIGStl (ORCPT ); Fri, 7 Sep 2018 14:49:41 -0400 Received: by mail.bootlin.com (Postfix, from userid 110) id 7452120799; Fri, 7 Sep 2018 16:08:33 +0200 (CEST) Received: from bbrezillon (AAubervilliers-681-1-30-219.w90-88.abo.wanadoo.fr [90.88.15.219]) by mail.bootlin.com (Postfix) with ESMTPSA id 1B51920701; Fri, 7 Sep 2018 16:08:23 +0200 (CEST) Date: Fri, 7 Sep 2018 16:08:22 +0200 From: Boris Brezillon To: Masahiro Yamada Cc: linux-mtd@lists.infradead.org, Miquel Raynal , devicetree@vger.kernel.org, Rob Herring , Dinh Nguyen , linux-kernel@vger.kernel.org, Marek Vasut , Brian Norris , Richard Weinberger , David Woodhouse , Mark Rutland Subject: Re: [PATCH] mtd: rawnand: denali: add DT property to specify skipped bytes in OOB Message-ID: <20180907160822.319047c8@bbrezillon> In-Reply-To: <1536317783-4942-1-git-send-email-yamada.masahiro@socionext.com> References: <1536317783-4942-1-git-send-email-yamada.masahiro@socionext.com> X-Mailer: Claws Mail 3.15.0-dirty (GTK+ 2.24.31; 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 Hi Masahiro, On Fri, 7 Sep 2018 19:56:23 +0900 Masahiro Yamada wrote: > NAND devices need additional data area (OOB) for error correction, > but it is also used for Bad Block Marker (BBM). In many cases, the > first byte in OOB is used for BBM, but the location actually depends > on chip vendors. The NAND controller should preserve the precious > BBM to keep track of bad blocks. > > In Denali IP, the SPARE_AREA_SKIP_BYTES register is used to specify > the number of bytes to skip from the start of OOB. The ECC engine > will automatically skip the specified number of bytes when it gets > access to OOB area. > > The same value for SPARE_AREA_SKIP_BYTES should be used between > firmware and the operating system if you intend to use the NAND > device across the control hand-off. > > In fact, the current denali.c code expects firmware to have already > set the SPARE_AREA_SKIP_BYTES register, then reads the value out. > > If no firmware (or bootloader) has initialized the controller, the > register value is zero, which is the default after power-on-reset. > > In other words, the Linux driver cannot initialize the controller > by itself. You cannot support the reset control either because > resetting the controller will get register values lost. > > This commit adds a way to specify it via DT. If the property > "denali,oob-skip-bytes" exists, the value will be set to the register. Hm, do we really need to make this config customizable? I mean, either you have a large-page NAND (page > 512 bytes) and the 2 first bytes must be reserved for the BBM or you have a small-page NAND and the BBM is at position 4 and 5. Are you sure people configure that differently? Don't you always have SPARE_AREA_SKIP_BYTES set to 6 or 2? Regards, Boris