From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: Re: [PATCH 1/5] dmaengine: dw_dmac: move to generic DMA binding Date: Wed, 30 Jan 2013 15:18:37 +0530 Message-ID: References: <1359395857-1235-1-git-send-email-arnd@arndb.de> <201301291621.59425.arnd@arndb.de> <201301300941.35886.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <201301300941.35886.arnd-r2nGTMty4D4@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: "devicetree-discuss" To: Arnd Bergmann Cc: Vinod Koul , devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, spear-devel , Andy Shevchenko , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: devicetree@vger.kernel.org On Wed, Jan 30, 2013 at 3:11 PM, Arnd Bergmann wrote: > On Wednesday 30 January 2013, Viresh Kumar wrote: >> I knew you will come to this :) >> So, the hardware is like: there are 16 request line slots per master, a >> platform can choose to connect same or separate devices to these. >> >> So, these are really 16 per master. > > Ok, I see. Do you know how these are numbered in the data sheet? > > If the convention is to have subsequent numbers for these in the > hardware description, we should probably just have that single > request number in the binding, too, and calculate the master number > from that. If it lists pairs of request/master number, we should > use pairs in the binding as well, in the same order. Actually what would be better to have is: - have this range from 0-15 only - together with the master we want to use for peripheral this should be enough. Datasheet of dw_dmac doesn't tell much about it.. just four bits for programming it and so values are from 0-15 :) >> > Ok. Would it be enough to have only one master and one request >> > field in the DT dma descriptor then, and have the code figure >> > whether to use it as source or destination, based on the >> > configuration? Which one should come first? Since you have >> > multiple masters per controller, and multiple requests per >> > master, it sounds like the cleanest descriptor form would >> > be >> > >> > ; >> > >> > Or possibly >> > >> > ; >> > >> > if the direction needs to be known at the time the channel >> > is requested. >> >> Its better to keep masters as is. So, that we can use appropriate >> masters for peripheral and memory to make the transfer fast. > > So you mean keep the format as > > ; > > ? Yes..