Based on an email from Paul Burton, quoting section 4.8 "Cacheability and
Coherency Attributes and Access Types" of "MIPS Architecture Volume 1:
Introduction to the MIPS32 Architecture" (MD00080, revision 6.01).
Signed-off-by: Christoph Hellwig <h...@lst.de>
---
arch/mips/Kconfig | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index fc88f68ea1ee..aff1cadeea43 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1119,6 +1119,13 @@ config DMA_PERDEV_COHERENT
config DMA_NONCOHERENT
bool
+ #
+ # MIPS allows mixing "slightly different" Cacheability and Coherency
+ # Attribute bits. It is believed that the uncached access through
+ # KSEG1 and the implementation specific "uncached accelerated" used
+ # by pgprot_writcombine can be mixed, and the latter sometimes provides
+ # significant advantages.
+ #
select ARCH_HAS_DMA_WRITE_COMBINE
select ARCH_HAS_SYNC_DMA_FOR_DEVICE
select ARCH_HAS_UNCACHED_SEGMENT
--
2.20.1
