Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760598Ab3EBRCa (ORCPT ); Thu, 2 May 2013 13:02:30 -0400 Received: from mga03.intel.com ([143.182.124.21]:51693 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753432Ab3EBRC2 (ORCPT ); Thu, 2 May 2013 13:02:28 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.87,597,1363158000"; d="scan'208";a="296631994" Date: Thu, 2 May 2013 21:58:37 +0530 From: Vinod Koul To: Guennadi Liakhovetski Cc: linux-sh@vger.kernel.org, Magnus Damm , Arnd Bergmann , Tony Lindgren , devicetree-discuss@lists.ozlabs.org, linux-kernel@vger.kernel.org, Russell King Subject: Re: [PATCH/RFC 0/4] dmaengine: add DT support for DMA multiplexers Message-ID: <20130502162837.GM1960@intel.com> References: <1367305883-2997-1-git-send-email-g.liakhovetski@gmx.de> <20130430104354.GF1960@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2546 Lines: 48 On Tue, Apr 30, 2013 at 02:17:13PM +0200, Guennadi Liakhovetski wrote: > (added Russell to CC, sorry for not including initially) > > Hi Vinod > > On Tue, 30 Apr 2013, Vinod Koul wrote: > > > On Tue, Apr 30, 2013 at 09:11:19AM +0200, Guennadi Liakhovetski wrote: > > > Previously an issue has been discussed, arising on sh-/r-mobile ARM-based > > > systems. There we typically have multiple DMA controller instances with > > > exactly equal or very similar capabilities. Each of them can serve the same > > > slaves, using the same slave identifiers (request line IDs). With the > > > present DMA DT implementation _each_ such DMA slave would have to reference > > > _each_ of those DMA controllers in its DMA bindings, e.g. > > But why... if that is the case then we havent define DT-bindings clearly enough > > Sorry, what do you mean "why?" Why each slave has to reference each DMA > controller? We have discussed this A LOT before... My understanding is, > that we decided, that the sh-/r-mobile case of multiple equal DMA > controllers is an exception and that we don't want to punish everyone for > it. So, the design includes only explicit requesting of specific DMA > request lines on specific DMA controllers, no wild-cards. If a slave DMA > channel can be provided by several DMA controllers we decided to list them > all explicitly too. And for the sh-/r-mobile case a DMA-mux DT node has > been proposed. This is exactly what this patch series is implementing. Is > my understanding wrong? > > > And we havent merged that yet, so why not fix that in first set itself > > Sorry, don't understand. The series isn't merged yet, that's right. That's > why I explicitly mention this dependency here. But this isn't a fix. This > is a new feature. The first patch-series only touches a specific DMA > controller driver and relevant platforms. No core changes, so, it's not > that intrusive and can be applied quickly. Whereas this series affects the > core and might need a more careful consideration, discussion, etc. What i mean from above is if we were already defining the sh-DT binding then why wasnt this taken care in the orignal definition? It would make sense to have proper binding which works well for both of these case, why a two shot approach? -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/