From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [94.23.35.102] (helo=mail.free-electrons.com) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1V4A95-0007YV-LP for linux-mtd@lists.infradead.org; Tue, 30 Jul 2013 13:39:24 +0000 Date: Tue, 30 Jul 2013 10:38:53 -0300 From: Ezequiel Garcia To: Daniel Mack Subject: Re: [PATCH 00/13] pxa3xx patches to support mvebu builds Message-ID: <20130730133852.GD2375@localhost> References: <1375140263-2028-1-git-send-email-ezequiel.garcia@free-electrons.com> <51F76EBA.1020504@gmail.com> <20130730095310.38400ca6@skate> <51F772FC.90404@gmail.com> <20130730101809.7c28525c@skate> <20130730131538.GB2375@localhost> <51F7BE11.2020101@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <51F7BE11.2020101@gmail.com> Cc: Lior Amsalem , Thomas Petazzoni , Jason Cooper , Artem Bityutskiy , leiwen@marvell.com, haojian.zhuang@gmail.com, Chao Xie , linux-mtd@lists.infradead.org, grinberg@compulab.co.il, Gregory Clement , eric.miao@marvell.com, computersforpeace@gmail.com, David Woodhouse , Willy Tarreau , nikita@compulab.co.il List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Jul 30, 2013 at 03:22:25PM +0200, Daniel Mack wrote: [...] > > Mmmm.. I'm a bit confused by this: is your dmaengine driver any > > different/better from the already existent mmp_{p,t}dma.c ? > > As I said, I saw this after I started my own implementation, which isn't > a big deal. At least, I now understand the internals of dmaengine > drivers :) The mmp_pdma looks suitable for PXA2xx chips, but it doesn't > work yet for me. I'll try and fix this first, and then port over all the > drivers. > > > Here's a patch posted in July 2012 converting pxa3xx-nand to dmaengine. > > Where? > Ouch... here it is: http://permalink.gmane.org/gmane.linux.ports.arm.kernel/178989 (sorry about that...) That patch was part of this series: http://comments.gmane.org/gmane.linux.ports.arm.kernel/181731 But as you can see in the above link, they dropped the pxa3xx-nand part. > > That patch was never merged because (just as Thomas says) both > > dma drivers (mmp dmaengine on one side, mach-pxa dma on the other) don't > > work together. In other words, you have to convert *all* drivers at the > > same time. > > > > Thomas proposed an idea for this conversion a few months ago: (quoting > > him from IRC) > > > > """ > > First have a patch that reimplements the existing plat-pxa/dma.c API on > > top of dmaengine, so that you don't have to change any driver. > > Then, go through each driver, one per patch to switch to the dmaengine API. > > And finally get rid of the compatibility layer created in the first > > patch. > > """ > > > > Does this sound sane? > > Unfortunately, no. I thought so too, but the problem is that all users > of the proprietary PXA DMA implementation access the registers directly, > and also allocate their own DMA coherent register space, which is > unneeded with a proper dmaengine implementation. > > So there's nothing else we can do than really change all the drivers, > which is what I'm currently doing. Oh, I see. > I'll put you on Cc: once I post patches. > Great! That'll be very appreciated. -- Ezequiel García, Free Electrons Embedded Linux, Kernel and Android Engineering http://free-electrons.com