Messages in this thread | | | From | Paul Burton <> | Subject | Re: [PATCH 4/7] dma-direct: provide generic support for uncached kernel segments | Date | Wed, 1 May 2019 17:40:34 +0000 |
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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: > > 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 :)
> > 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
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