From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: [PATCH 1/5] dmaengine: dw_dmac: move to generic DMA binding Date: Tue, 29 Jan 2013 15:45:40 +0200 Message-ID: <1359467140.31148.41.camel@smile> References: <1359395857-1235-1-git-send-email-arnd@arndb.de> <201301291035.30265.arnd@arndb.de> <201301291331.48427.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <201301291331.48427.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 , Viresh Kumar , devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, spear-devel , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: devicetree@vger.kernel.org On Tue, 2013-01-29 at 13:31 +0000, Arnd Bergmann wrote: > On Tuesday 29 January 2013, Viresh Kumar wrote: > > You can still keep fargs as is and just fill them as: > > > > fargs.cfg_lo = 0; > > > > if (DMA_TO_DEV) > > // dest is periph > > fargs.cfg_hi = be32_to_cpup(dma_spec->args+0) << 11; > > else if (DEV_TO_DMA) > > // src is periph > > fargs.cfg_hi = be32_to_cpup(dma_spec->args+0) << 7; > > > > The field size is 4 bits. > > Ah, good. So I guess the "dma-requests" property should actually > be "16" then. > > Does this mean that an implicit zero request line means memory? No, it doesn't. When dma is doing mem2mem transfers the request line field is ignored by the hw. > Could we have device-to-device DMAs with this controller, and if > we can, should we have both 'src' and 'dst' fields? As far as I know there is no driver under dmaengine that supports per2per transfers. > Are the > two number ranges sharing the same address space, i.e. is > request '7' as the destination guaranteed to be the same device > as request '7' in the source? Request line should be unique. It means a real wire from slave hw to the dmac. -- Andy Shevchenko Intel Finland Oy