MIPS: Support per-device DMA coherence

On some MIPS systems, a subset of devices may have DMA coherent with CPU
caches. For example in systems including a MIPS I/O Coherence Unit
(IOCU), some devices may be connected to that IOCU whilst others are
not.

Prior to this patch, we have a plat_device_is_coherent() function but no
implementation which does anything besides return a global true or
false, optionally chosen at runtime. For devices such as those described
above this is insufficient.

Fix this by tracking DMA coherence on a per-device basis with a
dma_coherent field in struct dev_archdata. Setting this from
arch_setup_dma_ops() takes care of devices which set the dma-coherent
property via device tree, and any PCI devices beneath a bridge described
in DT, automatically.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14349/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 86d5b3930531..235643970517 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1099,6 +1099,10 @@ config DMA_MAYBE_COHERENT
 	select DMA_NONCOHERENT
 	bool
 
+config DMA_PERDEV_COHERENT
+	bool
+	select DMA_MAYBE_COHERENT
+
 config DMA_COHERENT
 	bool