[Intel-gfx] [PATCH] drm/i915: Don't let a device flush to prepare buffers clear new write_domains.

[Keith Packard]

On Fri, 2009-02-20 at 12:12 +0000, Chris Wilson wrote:

> Whilst looking at the domain checking, I think one case is missing
> during the validation. AIUI, a write object must have read_domains ==
> write_domain.

That's certainly makes things easier to understand, but it's not
necessary. Imagine a batch buffer which first reads through the texture
cache and then writes to the same object through the render cache. That
batch buffer would need to ensure that both texture and render caches
were prepared for reading and then it would leave the buffer with data
in the render cache.

You'll see that Eric also posted a patch to Mesa which eliminated one
case where it (incorrectly) specified texture|render, render. That fixed
lots of Mesa issues even without having the GEM bug fixed.

-- 
keith.packard at intel.com
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