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    SubjectRe: [PATCH 02/20] dma-mapping: provide a generic dma-noncoherent implementation
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    On 05/18/2018 06:23 AM, hch@lst.de wrote:
    > Fri, May 18, 2018 at 01:03:46PM +0000, Alexey Brodkin wrote:
    >> Note mmc_get_dma_dir() is just "data->flags & MMC_DATA_WRITE ? DMA_TO_DEVICE : DMA_FROM_DEVICE".
    >> I.e. if we're preparing for sending data dma_noncoherent_map_sg() will have DMA_TO_DEVICE which
    >> is quite OK for passing to dma_noncoherent_sync_sg_for_device() but in case of reading we'll have
    >> DMA_FROM_DEVICE which we'll pass to dma_noncoherent_sync_sg_for_device() in dma_noncoherent_map_sg().
    >>
    >> I'd say this is not entirely correct because IMHO arch_sync_dma_for_cpu() is supposed to only be used
    >> in case of DMA_FROM_DEVICE and arch_sync_dma_for_device() only in case of DMA_TO_DEVICE.
    > arc overrides the dir paramter of the dma_sync_single_for_device/
    > dma_sync_single_for_cpu calls. My patches dropped that, and I have
    > restored that, and audit for the other architectures is pending.

    Right, for now lets retain that and do a sweeping audit of @direction - to me it
    seems extraneous (as it did 10 years ago), but I'm not an expert in this are so
    perhaps it is needed for some device / arches and it would be good to understand
    that finally.

    > That being said the existing arc code still looks rather odd as it
    > didn't do the same thing for the scatterlist versions of the calls.
    > I've thrown in a few patches into my new tree to make the sg versions
    > make the normal calls, and to clean up the area a bit.

    Not calling names or anything here, but it doesn't exist for sg variants, because
    I didn't write that code :-)
    It was introduced by your commi:

    2016-01-20 052c96dbe33b arc: convert to dma_map_ops

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