On 08/15/2015 01:42 AM, Laurent Pinchart wrote: > Hi Geert, > > On Thursday 16 July 2015 20:36:49 Geert Uytterhoeven wrote: >> Hi Laurent, >> >> While working on DMA for R-Car Gen2 using the sh-sci serial driver with >> rcar-dmac, I ran into two issues: >> >> 1. Unlike the old shdmac DMA engine driver, the new rcar-dmac DMA >> engine driver does not support resubmitting a DMA descriptor. >> I first tried the patch below, until I ran into the race condition, >> after which I changed sh-sci to not reuse DMA descriptors. > > Is reusing descriptors something that the DMA engine API explicitly allows ? No. It explicitly forbids it. dmaengine_submit() must always be called in a pair with dmaenine_prep_*(). But there is some work in-progress to add support for re-usable descriptors, see http://www.spinics.net/lists/dmaengine/msg05554.html -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
