On Mon, Oct 14, 2019 at 08:31:02PM +0200, Nicolas Saenz Julienne wrote:

the Raspberry Pi 4 offers up to 4GB of memory, of which only the first
is DMA capable device wide. This forces us to use of bounce buffers,
which are currently not very well supported by ARM's custom DMA ops.
Among other things the current mechanism (see dmabounce.c) isn't
suitable for high memory. Instead of fixing it, this series introduces a
way of selecting dma-direct as the default DMA ops provider which allows
for the Raspberry Pi to make use of swiotlb.

I presume these patches go on top of this series:

http://lkml.kernel.org/r/20190911182546.17094-1-nsaenzjulienne@suse.de

which I queued here:

https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/zone-dma

-- 
Catalin