On Tue, May 12, 2015 at 8:37 AM, Maxime Ripard <maxime.rip...@free-electrons.com> wrote: > Hi, > > This serie refactors the mv_xor in order to support the latest Armada > 38x features, including the PQ support in order to offload the RAID6 > PQ operations. > > Not all the PQ operations are supported by the XOR engine, so we had > to introduce new async_tx flags in the process to identify > un-supported operations. > > Please note that this is currently not usable because of a possible > regression in the RAID stack in 4.1 that is being discussed at the > moment here: https://lkml.org/lkml/2015/5/7/527
This is problematic as async_tx is a wart on the dmaengine subsystem and needs to be deprecated, I just have yet to find the time to do that work. It turns out it was a mistake to hide the device details from md, it should be explicitly managing the dma channels, not relying on a abstraction api. The async_tx api usage of the dma-mapping api is broken in that it relies on overlapping mappings of the same address. This happens to work on x86, but on arm it needs explicit non-overlapping mappings. I started the work to reference count dma-mappings in 3.13, and we need to teach md to use dmaengine_unmap_data explicitly. Yielding dma channel management to md also results in a more efficient implementation as we can dma_map() the stripe cache once rather than per-io. The "async_tx_ack()" disaster can also go away when md is explicitly handling channel switching. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
