From mboxrd@z Thu Jan 1 00:00:00 1970 From: andriy.shevchenko@linux.intel.com (Andy Shevchenko) Date: Tue, 29 Jan 2013 15:45:40 +0200 Subject: [PATCH 1/5] dmaengine: dw_dmac: move to generic DMA binding In-Reply-To: <201301291331.48427.arnd@arndb.de> References: <1359395857-1235-1-git-send-email-arnd@arndb.de> <201301291035.30265.arnd@arndb.de> <201301291331.48427.arnd@arndb.de> Message-ID: <1359467140.31148.41.camel@smile> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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