On Wed, Aug 24, 2016 at 9:58 AM, Peter Ujfalusi <peter.ujfalusi@xxxxxx> wrote: > On 08/23/16 13:12, Ran Shalit wrote: >>> The sDMA dmaengine driver was introduced with 3.6, the memcpy support is >>> coming in at 4.2. >>> In 3.4 you only have the legacy omap-dma support. This explains why the >>> /sys/class/dma/ is empty for you. >>> >> >> Peter, >> Thank you very much. >> >> It seems that I can't upgrade the kernel at this point of development. >> So, I will have to do it with legacy API (since I can't updared) using >> omap-dma.c , memcpy transfer , 16-bits. >> I think it is possible, Right ? > > Sure, if there is no dmaengine for sDMA, the legacy API is the only way to use > sDMA. It is just a matter of how you configure the omap-dma, the API allows > pretty much to use all features of sDMA. > >> I see there is also example (mcbsp.c) for using legacy in: >> ftp://ftp.oregonstate.edu/.2/nslu2/sources/git/git.openmoko.org.git.kernel.git/arch/arm/plat-omap/mcbsp.c > > Hrm, this is more like 2.6.29-ish code... > >> As I understand, the transfer word length is set with >> omap_set_dma_transfer_params(), used with OMAP_DMA_DATA_TYPE_S16 for >> 16-bits with . > > McASP is using hw trigger, not sw trigger. It is not memcpy at all. Not sure > if 2.6.29 had any memcpy users of sDMA. > >> Another last thing: >> Do we need to confure dma channels in board file (I can't see any >> reference to dma) ? > > This is only needed if the device have DMA request. In that case you want to > have the hw request number as DMA resource on the device. But for memcpy you > should not have hw request number as memcpy is sw triggered. > Dear Peter, If I may please ask one more on dma issue, with legacy api: 1. How do we choose word length 16 bits, is it by using OMAP_DMA_DATA_TYPE_S16 with: omap_set_dma_transfer_params(tx->dma_ch, OMAP_DMA_DATA_TYPE_S16, ...) 2. I did not understand how to specify memoty-to-memory (sw trigger). Is sw trigger same as burst mode ? When should we use burst mode ? (I did not find documentation for klegacy api, so I'm not sure, it also contain burst length which I am not sure which value I should use in) Do you think /drivers/media/video/omap/omap_vout_frfb.c can be suited as example for memory-to-memory ? Regards, Ran > >> Thank you, >> Ran >> >>>> >> >>>>>> >>>>>> >>>>>> Regards, >>>>>> Ran >>>>>> >>>>>> >>>>>>>> >>>>>>>>> >>>>>>>>>> 2.Is there any example which shows how to use DMA (which shall call >>>>>>>>>> the edma, and shall result in triggering a dma trsnaction in OMAP) ? >>>>>>>>> >>>>>>>>> git grep dmaengine_prep_dma_sg >>>>>>>>> or >>>>>>>>> git grep dmaengine_terminate_all >>>>>>>>> >>>>>>>>> will show you the drivers using dmaengine. >>>>>>>>> >>>>>>>>> -- >>>>>>>>> Péter >>>>>>>> >>>>>>> >>>>>>> >>>>>>> -- >>>>>>> Péter >>>>> >>>>> >>>>> -- >>>>> Péter >>> >>> >>> -- >>> Péter > > > -- > Péter -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
