From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754480AbaIQIe7 (ORCPT ); Wed, 17 Sep 2014 04:34:59 -0400 Received: from mail-bl2on0113.outbound.protection.outlook.com ([65.55.169.113]:4768 "EHLO na01-bl2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751660AbaIQIe4 (ORCPT ); Wed, 17 Sep 2014 04:34:56 -0400 Date: Wed, 17 Sep 2014 16:41:22 +0800 From: Robin Gong To: Lucas Stach CC: , , , , , , , , , , Subject: Re: [PATCH v2] ARM: dts: imx6dl: disable dma support for spi on i.mx6dl Message-ID: <20140917084120.GA6369@Robin-OptiPlex-780> References: <1410327012-31185-1-git-send-email-b38343@freescale.com> <1410774073.3314.1.camel@pengutronix.de> <20140916034123.GA20800@Robin-OptiPlex-780> <1410861006.2746.1.camel@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1410861006.2746.1.camel@pengutronix.de> User-Agent: Mutt/1.5.21 (2010-09-15) X-EOPAttributedMessage: 0 X-Forefront-Antispam-Report: CIP:192.88.168.50;CTRY:US;IPV:CAL;IPV:NLI;EFV:NLI;SFV:NSPM;SFS:(10019020)(6009001)(189002)(51444003)(199003)(51704005)(24454002)(50466002)(6806004)(102836001)(31966008)(20776003)(77982003)(19580395003)(104016003)(84676001)(44976005)(21056001)(23726002)(68736004)(4396001)(97736003)(83322001)(93886004)(92566001)(15202345003)(81342003)(87936001)(33716001)(33656002)(50986999)(83072002)(26826002)(54356999)(76176999)(80022003)(99396002)(83506001)(15975445006)(90102001)(79102003)(85852003)(74662003)(64706001)(95666004)(47776003)(107046002)(105606002)(46406003)(106466001)(97756001)(76482002)(81542003)(74502003)(92726001)(110136001)(85306004)(46102003)(32563001)(42262002);DIR:OUT;SFP:1102;SCL:1;SRVR:BL2PR03MB339;H:tx30smr01.am.freescale.net;FPR:;MLV:ovrnspm;PTR:InfoDomainNonexistent;MX:1;A:1;LANG:en; X-Microsoft-Antispam: UriScan:; X-Microsoft-Antispam: BCL:0;PCL:0;RULEID:;SRVR:BL2PR03MB339; X-Forefront-PRVS: 0337AFFE9A Authentication-Results: spf=fail (sender IP is 192.88.168.50) smtp.mailfrom=yibin.gong@freescale.com; X-OriginatorOrg: freescale.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 16, 2014 at 11:50:06AM +0200, Lucas Stach wrote: > Hi Robin, > > Am Dienstag, den 16.09.2014, 11:41 +0800 schrieb Robin Gong: > > Hi Lucas, > > I understood your concern,but looks we have to break old DT. > > Sorry, but this isn't going to happen. And honestly I don't even see the > need to do so. > > > Our old DT > > support SPI DMA on i.mx6q/dl(v2,b3810c3dc1bcbc6a), but the DMA support patch > > for SPI driver is still in reviewing(v6). > > So this means now is the time to fix this driver patch to not enable DMA > on imx6dl. Nobody will experience any breakage in this case. > Sorry, i.mx6q and i.mx6dl are totally same, not only IP but also clock. So we can't distinguish them except for different compatible name.... > > So the violation you mentioned comes > > if someone use the DT during the time(from v2 to spi driver patch upstreamed). > > The different behaviors on different chips(only i.mxdl can't pass strength > > test) are just found from last month, this is why I sent the patch for disable > > SPI DMA support on i.mx6dl during I sent v6 patch for spi driver. I think that's > > make sense, because DTs are also in development, new difference between different > > chips maybe found in the future although they share the same IP.... > > Yes, I can check cpu type by looking at DT in spi driver, but it's not nice. > > Yeah it would have been nicer if we had an explicit DT compatible for > the imx6dl ecspi version, but it's not there, so we have to cope with > this. > > > So I'm afraid that we have to break the old DTs in the gap between the two > > levels patch accepted cycle. > > > > On Mon, Sep 15, 2014 at 11:41:13AM +0200, Lucas Stach wrote: > > > Am Mittwoch, den 10.09.2014, 13:30 +0800 schrieb Robin Gong: > > > > There is one weird data in rxfifo after one full rx/tx transfer > > > > done sometimes. It looks a design issue and hard to workaround > > > > totally, so disable dma functhion here. And will re-enable it > > > > once the root cause found. > > > > > > > Sorry, I'm late to this as Shawn seems to already have picked up this > > > patch, but this isn't the right way to fix the problem. > > > > > > We made it clear at kernel summit last year that we try to not break > > > existing DTs as booting a new kernel with an old DT is a valid use case. > > > While you don't strictly violate this rule what you do here is only > > > fixing systems booting with a new DT while leaving others broken. > > > > > > If you are working around a hardware problem please disable DMA support > > > in the driver. This will also allow you to enable it again, if you find > > > another workaround without touching the DT again. > > > > > > So this patch gets a NAK from me. > > > > > Regards, > Lucas > -- > Pengutronix e.K. | Lucas Stach | > Industrial Linux Solutions | http://www.pengutronix.de/ | >