Hi Christoph,

On Wed, May 01, 2019 at 07:29:12PM +0200, Christoph Hellwig wrote:

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

quoted

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.

Ah, of course, I clearly require more caffeine :)

quoted

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.

Great; using cached writes would match the existing MIPS behavior.

Thanks,
    Paul