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Date: Thu, 30 Aug 2018 10:59:37 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Ezequiel Garcia <ezequiel@collabora.com>
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Subject: Re: [RFC 3/3] stk1160: Use non-coherent buffers for USB transfers
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> +	dma_sync_single_for_cpu(&urb->dev->dev, urb->transfer_dma,
> +		urb->transfer_buffer_length, DMA_FROM_DEVICE);

You can't ue dma_sync_single_for_cpu on non-coherent dma buffers,
which is one of the major issues with them.