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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A3C91C433F5 for ; Tue, 22 Feb 2022 14:28:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-ID:References:In-Reply-To:Subject:Cc:To:From :Date:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=pBsyUfimKvvGa31WnVibzsiABTPK9qS6VId27UhB4SQ=; b=nNJJhn+8vxU2r5O35nUyd9UlXc LtUrKPMgOaKKerpxjOAA9mtwkYgDGyS4lPOFWiUJV2+33jeBqZEiMSrU2lfOaErBaWygc17H1VWWt JszrYZnCpMyMBjwfJ+GS4lAS1D7N0bulAiaODHZNFRX46ZhlTVmhbGs9C5tklbHG1UdveRv+0NrAm TIp8WxLaHFeHSHJ+LneU5XrTc0/s9eOwlkIN60fyzLxt3+Zyunv7g5aHC45PoAIWs0dSwsg9M5q5z H5bfcB1aWMrIAa1t+9arxX6IakUAZCAHd8GTYumGULx3SDWDd7fN6xpBqHR90JDvcQkqtx3cmrork lnj2+caQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nMW8s-009tiW-VG; Tue, 22 Feb 2022 14:27:51 +0000 Received: from ssl.serverraum.org ([176.9.125.105]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nMW8o-009tge-5E for linux-mtd@lists.infradead.org; Tue, 22 Feb 2022 14:27:48 +0000 Received: from ssl.serverraum.org (web.serverraum.org [172.16.0.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id 6FFDE22205; Tue, 22 Feb 2022 15:27:44 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1645540064; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8dj0piB+942CQbs7XIdKdDi92gQwu/L2SA425BJSZIw=; b=ktuPX8BKiZqDpYwucvTcKBislX13mpMQ+qRPl2YCsKBgJ7lC9fxFZtsETlzyl7sNWWtTkP VV37FTzWj3GngcMe/KCdXOSn5dkIo/qR5uJBlK81gMsRWZegjuwhPyEkdbCh5Zcjz/pPIM AG5HZLtdFM5XS5xImsEXMgP1b3pHdkQ= MIME-Version: 1.0 Date: Tue, 22 Feb 2022 15:27:44 +0100 From: Michael Walle To: Tudor.Ambarus@microchip.com Cc: p.yadav@ti.com, broonie@kernel.org, miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com, linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, Nicolas.Ferre@microchip.com, zhengxunli@mxic.com.tw, jaimeliao@mxic.com.tw Subject: Re: [PATCH 0/4] spi-mem: Allow specifying the byte order in DTR mode In-Reply-To: <7cd74ef3-5a7d-4e65-3436-ee3399ca56a3@microchip.com> References: <20220218145900.1440045-1-tudor.ambarus@microchip.com> <44f655d027b49b87065915f6ba2744d2@walle.cc> <81d7c569-d6c2-9167-e007-eda72f34842b@microchip.com> <23fbbf2dde387e3832b4ca23d46816c0@walle.cc> <7cd74ef3-5a7d-4e65-3436-ee3399ca56a3@microchip.com> User-Agent: Roundcube Webmail/1.4.12 Message-ID: X-Sender: michael@walle.cc X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220222_062746_402260_85F007E1 X-CRM114-Status: GOOD ( 15.82 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org Am 2022-02-22 15:23, schrieb Tudor.Ambarus@microchip.com: > On 2/22/22 16:13, Michael Walle wrote: >> EXTERNAL EMAIL: Do not click links or open attachments unless you know >> the content is safe >> >> Am 2022-02-22 14:54, schrieb Tudor.Ambarus@microchip.com: >>> On 2/21/22 09:44, Michael Walle wrote: >>>> EXTERNAL EMAIL: Do not click links or open attachments unless you >>>> know >>>> the content is safe >>>> >>>> Am 2022-02-18 15:58, schrieb Tudor Ambarus: >>>>> Fortunately there are controllers >>>>> that can swap back the bytes at runtime, fixing the endiannesses. >>>>> Provide >>>>> a way for the upper layers to specify the byte order in DTR mode. >>>> >>>> Are there any patches for the atmel-quadspi yet? What happens if >>> >>> not public, but will publish them these days. >>> >>>> the controller doesn't support it? Will there be a software >>>> fallback? >>> >>> no need for a fallback, the controller can ignore >>> op->data.dtr_bswap16 >>> if >>> it can't swap bytes. >> >> I don't understand. If the controller doesn't swap the 16bit values, >> you will read the wrong content, no? >> > > In linux no, because macronix swaps bytes on a 2 byte boundary both on > reads and on page program. The problem is when you mix 8D-8D-8D mode > and > 1-1-1 mode along the boot stages. Let's assume you write all boot > binaries > in 1-1-1 mode. When reaching u-boot if you enable 8D-8D-8D mode, when > u-boot > will try to get the kernel it will fail, as the flash swaps the bytes > compared > to what was written with 1-1-1 mode. You write D0 D1 D2 D3 in 1-1-1 > mode and > when reaching u-boot you will read D1 D0 D3 D2 and it will mess the > kernel image. But you have to consider also 3rd parties, like an external programmer or another OS. So, there has to be *one correct* way of writing/reading these bytes. -michael ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/