On Wed, May 01, 2019 at 05:18:59PM +0000, Paul Burton wrote:

I'm not so sure about this part though.

On MIPS we currently don't clear the allocated memory with memset. Is
doing that really necessary?

We are clearling it on mips, it is inside dma_direct_alloc_pages.

If it is necessary then as-is this code will clear the allocated memory
using uncached writes which will be pretty slow. It would be much more
efficient to perform the memset before arch_dma_prep_coherent() & before
converting ret to an uncached address.

Yes, we could do that.