Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH] drm/i915: check to see if SIMD registers are available before using SIMD | Date | Mon, 4 May 2020 16:15:41 +0000 |
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From: Christoph Hellwig > Sent: 04 May 2020 17:03 > > On Sun, May 03, 2020 at 09:20:19PM +0100, Chris Wilson wrote: > > > Err, why does i915 implements its own uncached memcpy instead of relying > > > on core functionality to start with? > > > > What is this core functionality that provides movntqda? > > A sensible name might be memcpy_uncached or mempcy_nontemporal. > But the important point is that this should be arch code with a common > fallback rather than hacking it up in drivers.
More the point, you are trying to do a copy where: 1) The kernel isn't expected to read the data - so can bypass the cache. and maybe: 2) The data needs flushing from the cache to actual memory. and maybe: 3) The cache lines need invalidating.
The fallbacks depend on the required behaviour.
David
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