dma-direct: rename and cleanup __phys_to_dma

The __phys_to_dma vs phys_to_dma distinction isn't exactly obvious. Try
to improve the situation by renaming __phys_to_dma to
phys_to_dma_unencryped, and not forcing architectures that want to
override phys_to_dma to actually provide __phys_to_dma.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>

dma-direct: remove __dma_to_phys

There is no harm in just always clearing the SME encryption bit, while
significantly simplifying the interface.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>

dma-direct: unify the dma_capable definitions

Currently each architectures that wants to override dma_to_phys and
phys_to_dma also has to provide dma_capable. But there isn't really
any good reason for that. powerpc and mips just have copies of the
generic one minus the latests fix, and the arm one was the inspiration
for said fix, but misses the bus_dma_mask handling.
Make all architectures use the generic version instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Reviewed-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>

MIPS: consolidate the swiotlb implementations

Octeon and Loongson share exactly the same code, move it into a common
implementation, and use that implementation directly from get_arch_dma_ops.

Also provide the expected dma-direct.h helpers directly instead of
delegating to platform dma-coherence.h headers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Patchwork: https://patchwork.linux-mips.org/patch/19534/
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: David Daney <david.daney@cavium.com>
Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Tom Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: iommu@lists.linux-foundation.org
Cc: linux-mips@linux-mips.org

dma-mapping: move swiotlb arch helpers to a new header

phys_to_dma, dma_to_phys and dma_capable are helpers published by
architecture code for use of swiotlb and xen-swiotlb only. Drivers are
not supposed to use these directly, but use the DMA API instead.

Move these to a new asm/dma-direct.h helper, included by a
linux/dma-direct.h wrapper that provides the default linear mapping
unless the architecture wants to override it.

In the MIPS case the existing dma-coherent.h is reused for now as
untangling it will take a bit of work.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Robin Murphy <robin.murphy@arm.com>