From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-199112-1520462491-2-16719652893549094745 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.25, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='com', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1520462491; b=dez//Zv3efCeZLpx0OKe04audS/YXuJn0+EkSmjC3dFFDSq eWvq2nv7N4QPaEEIFWCOE1o1fUoEfL3CzdVDciz8lywT0R8GhLouIdTxe6OgcjNV Y2dEBbHrKyQj0POIgIXr3t03z23C8JtT5rcgAlbfmrlWMbRLxlyRZNAgjngYM5FK +R7f6SIzBZVgVQ94jx5dNagWtHDuMacXqTsqhDqugbqedzT3Gn6DKsNnLO9GtecN ySC87fe3vVgPHtyBUUaUuCgbvfJlVqZFHTZ3YRRneuQBrI9XHsNW0PRTEkLDH+z6 uFOQ/TCMhgQequ87iCmdwGqxyfiKpPTAhl8YblQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :in-reply-to:references:mime-version:content-type :content-transfer-encoding:sender:list-id; s=arctest; t= 1520462491; bh=0fgQTNMnSxbjF+1EeXKTMIwnNGJH7OcID+ZNREO+kVA=; b=B RaNPE/6K65JeI0t8rumbXJD5pMpfkLxatobSY1qJGbdYjpCgkvPv9pQ2eGRX4WzO LZZpDrXR/ljTW+un9ERmAW17HMMnVkuKrNg08RMwk0C/Hw6SWnyS+Q6tz819+9Pb m6a5h21kgEUhyMX0+AebQLi5JoQFar1j1/LvvdSAAIvf0In+id/+8rIuImWyHDQ1 8VXzLcLLMsBfqF4BVTmRqbGPC05s0YSwKy+hZvyVgs518qzSLl2jy69J7lyh9XXG nDSqf1Z4YeV4BWX7QE1YqcMnbfhHPSBYN4vXZxGQcmwAGnFO8trKQbKtNGwBbBm+ 2oVz20ygiIASKlSG7AFYQ== ARC-Authentication-Results: i=1; mx1.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=bootlin.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-category=clean score=-100 state=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=bootlin.com header.result=pass header_is_org_domain=yes Authentication-Results: mx1.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=bootlin.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-category=clean score=-100 state=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=bootlin.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934087AbeCGWl2 convert rfc822-to-8bit (ORCPT ); Wed, 7 Mar 2018 17:41:28 -0500 Received: from mail.bootlin.com ([62.4.15.54]:56319 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933537AbeCGWl2 (ORCPT ); Wed, 7 Mar 2018 17:41:28 -0500 X-Remote-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on mail.bootlin.com X-Remote-Spam-Level: X-Remote-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,SHORTCIRCUIT, URIBL_BLOCKED shortcircuit=ham autolearn=disabled version=3.4.0 Date: Wed, 7 Mar 2018 23:40:51 +0100 From: Boris Brezillon To: Pavel Machek Cc: Richard Weinberger , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, cyrille.pitchen@wedev4u.fr, marek.vasut@gmail.com, boris.brezillon@free-electrons.com, computersforpeace@gmail.com, dwmw2@infradead.org, dedekind1@gmail.com, tharvey@gateworks.com, stable@vger.kernel.org Subject: Re: [PATCH] ubi: Reject MLC NAND Message-ID: <20180307234051.479d9eed@bbrezillon> In-Reply-To: <20180307214342.GA9852@amd> References: <20180303104554.5958-1-richard@nod.at> <20180306231805.GA28183@amd> <6772577.AmT7QaWTNU@blindfold> <20180307214342.GA9852@amd> 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=UTF-8 Content-Transfer-Encoding: 8BIT Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Wed, 7 Mar 2018 22:43:42 +0100 Pavel Machek wrote: > On Wed 2018-03-07 09:01:16, Richard Weinberger wrote: > > Pavel, > > > > Am Mittwoch, 7. März 2018, 00:18:05 CET schrieb Pavel Machek: > > > On Sat 2018-03-03 11:45:54, Richard Weinberger wrote: > > > > While UBI and UBIFS seem to work at first sight with MLC NAND, you will > > > > most likely lose all your data upon a power-cut or due to read/write > > > > disturb. > > > > In order to protect users from bad surprises, refuse to attach to MLC > > > > NAND. > > > > > > > > Cc: stable@vger.kernel.org > > > > > > That sounds like _really_ bad idea for stable. All it does is it > > > removes support for hardware that somehow works. > > > > MLC is not supported and does not work. Full stop. > > If someone manages to get it somehow work, either with hardware or software > > hacks they are on their own. > > Having it in stable is the only chance we have to get it into vendor > > kernels. > > Can you show how it meets the stable kernel criteria? They are > documented in tree. This should not be in stable. > > And I'd like to see changelog improved. Real reason MLC is not > supported is upper/lower page parts on MLC. And real fix to work with > bigger pages in UBI. Come on! Don't you think this would have been fixed already if it was that easy?! Have you looked at an MLC datasheet to see how paired pages are combined? If you had you would now that paired pages are almost all the time not contiguous, thus preventing the trick you're suggesting here. Please document yourself before doing such presumptuous statements (you can have a look at these slides if you want some details about why this is not so simple [1]). I'm definitely not saying supporting MLC NANDs in Linux is impossible, and if you're interested in working on this topic I'd be happy to help. But please don't block this patch without understanding what supporting MLC NANDs implies. [1]https://events.static.linuxfound.org/sites/events/files/slides/ubi-mlc.pdf -- Boris Brezillon, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com