[Intel-gfx] [PATCH] drm/i915: Fix frontbuffer tracking for PSR

[Chris Wilson]

On Sat, Jun 14, 2014 at 07:00:52AM +0100, Chris Wilson wrote:
> This should enable accurate frontbuffer tracking and keep PSR disabled
> whilst (and only while) the scanout is being directly accessed either by
> the CPU or by the GPU. The important difference here is that the
> tracking is more accurate and we check in the re-enable worker whether
> the fb is still being written to. This should allow legacy display
> servers to use PSR effectively, without breaking the special cases where
> the scanout is being written to directly and never flushed (for example
> after the display server is banned from the GPU). It also has the
> side-effect of working correctly with fbcon, by disabling PSR whilst
> fbcon is active.

Nope. userpsace messes up fbcon tracking by knocking it out of the write
domain by reading from it with the GPU. I think the correct answer here
is just to fix fbcon to do the correct domain tracking, and then it a
small step to adding the 100 lines or so to fully accelerate fbcon.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre