On 04/17/2018 12:58 PM, Sinan Kaya wrote: > On 4/17/2018 12:12 PM, Dave Jiang wrote: >> >> On 04/13/2018 07:12 PM, Sujeev Dias wrote: >>> Hi >>> >>> Can we please revert this patch because it breaks qcom dma-engine drivers and many consumers after >>> we propagated to 4.14 kernel. >>> >>> commit: c678fa66341c7b82a57cfed0ba3656162e970f99 >>> dmaengine: remove DMA_SG as it is dead code in kernel >>> >>> I don't see any alternate methods we can use either. We cannot use standard dma_memcpy >>> api's since argument for both src and destination dma_addr. Because dma mapping has to >>> be done by dma controller (due to smmu/sid configurations), client must pass host DDR >>> address as a cpu address not dma_addr. >>> >>> Thanks >>> Sujeev >>> >> Sujeev, >> At least IMO, when you don't have in kernel upstream consumer for the >> code, it's dead code for the kernel. In the end, it's Vinod's call. >> However, I do think in the future we will need support for DMA engines >> that want to take virtual memory addresses instead of DMA addresses with >> SMMU/SID type of implementation. So something new needs to be introduced.... > > If I remember this right, another implementation was going to replace DMA_SG. > DMA_SG got reverted but the new implementation wasn't put in place for some > reason. Yes I was in the process of pushing something but it ended up not being beneficial at this time so it on hold right now. Although the removal of DMA_SG was part of a clean up and not tied to that new functionality. If Vinod feel like it should be reverted I have no objection. I still would like to see proper support for virtual memory etc eventually. But at least for me it'll take a bit for me to get to work on that, but hopefully soon. > > Given we have few users of DMA Engine, I believe we should try to keep as > much functionality as possible in the kernel to allow new features to be > developed rather than limiting people's choices. > Would love to see more in kernel consumers for dmaengine. Maybe things that help accelerate core kernel bits? :) -- 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
