From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753074AbeDTWKi (ORCPT ); Fri, 20 Apr 2018 18:10:38 -0400 Received: from mail.bootlin.com ([62.4.15.54]:52705 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752647AbeDTWKh (ORCPT ); Fri, 20 Apr 2018 18:10:37 -0400 Date: Sat, 21 Apr 2018 00:10:28 +0200 From: Boris Brezillon To: NeilBrown Cc: Cyrille Pitchen , Marek Vasut , David Woodhouse , "Brian Norris" , Boris Brezillon , Richard Weinberger , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mtd: spi-nor: clear Winbond Extended Address Reg on switch to 3-byte addressing. Message-ID: <20180421001028.544f5d09@bbrezillon> In-Reply-To: <87efj9pnyk.fsf@notabene.neil.brown.name> References: <874lkmw54j.fsf@notabene.neil.brown.name> <87sh7wrq8p.fsf@notabene.neil.brown.name> <20180420215440.7b078f6c@bbrezillon> <87efj9pnyk.fsf@notabene.neil.brown.name> 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 21 Apr 2018 07:28:19 +1000 NeilBrown wrote: > On Fri, Apr 20 2018, Boris Brezillon wrote: > > > Hi Neil, > > > > On Mon, 16 Apr 2018 09:42:30 +1000 > > NeilBrown wrote: > > > >> Winbond spi-nor flash 32MB and larger have an 'Extended Address > >> Register' as one option for addressing beyond 16MB (Macronix > >> has the same concept, Spansion has EXTADD bits in the Bank Address > >> Register). > >> > >> According to section > >> 8.2.7 Write Extended Address Register (C5h) > >> > >> of the Winbond W25Q256FV data sheet (256M-BIT SPI flash) > >> > >> The Extended Address Register is only effective when the device is > >> in the 3-Byte Address Mode. When the device operates in the 4-Byte > >> Address Mode (ADS=1), any command with address input of A31-A24 > >> will replace the Extended Address Register values. It is > >> recommended to check and update the Extended Address Register if > >> necessary when the device is switched from 4-Byte to 3-Byte Address > >> Mode. > >> > >> So the documentation suggests clearing the EAR after switching to > >> 3-byte mode. Experimentation shows that the EAR is *always* one after > >> the switch to 3-byte mode, so clearing the EAR is mandatory at > >> shutdown for a subsequent 3-byte-addressed reboot to work. > >> > >> Note that some SOCs (e.g. MT7621) do not assert a reset line at normal > >> reboot, so we cannot rely on hardware reset. The MT7621 does assert a > >> reset line at watchdog-reset. > >> > >> Signed-off-by: NeilBrown > > > > We should probably backport the fix. Can you add a Fixes and Cc-stable > > tag? > > It's a bit weird having Fixes when this isn't a regression, but I guess > it doesn't hurt. Well, I thought you wanted this patch to be backported to stable releases, hence my suggestion. Of course it's not a regression, since the bug is here from the beginning, but nonetheless it's fixing a bug. > I chose > Fixes: 59b356ffd0b0 ("mtd: m25p80: restore the status of SPI flash when exiting") > as this patch it useless without that one. Not sure that's how Fixes should be used. IIUC, it should point to the first commit where the bug was introduced, so I guess it's 0aa87b7563f1 ("mtd: m25p80: add support for the windbond w25q256 chip") in this case. Now, if you want to restrict the kernel releases this patch should be backported to, you can use the '# vX.Y+' suffix in your Cc-stable tag. > > I also fixed the comment and have resent. Thanks.