Re: [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE

On Wed, 7 Aug 2019, Christoph Hellwig wrote:

Mips uses the KSEG1 kernel memory segment to map dma coherent
allocations for non-coherent devices as uncacheable, and does not have
any kind of special support for DMA_ATTR_WRITE_COMBINE in the allocation
path.  Thus supporting DMA_ATTR_WRITE_COMBINE in dma_mmap_attrs will
lead to multiple mappings with different caching attributes.

 FYI, AFAIK _CACHE_UNCACHED_ACCELERATED (where supported) is effectively 
write-combine.  Though IIUC someone would have to wire it in first.

  Maciej