[Intel-gfx] [PATCH 11/18] drm/i915: switch to default context on idle

[Chris Wilson]

On Thu, 29 Mar 2012 21:29:05 +0200, Daniel Vetter <daniel at ffwll.ch> wrote:
> On Sun, Mar 18, 2012 at 01:39:51PM -0700, Ben Widawsky wrote:
> > To keep things as sane as possible, switch to the default context before
> > idling. This should help free context objects, as well as put things in
> > a more well defined state before suspending.
> > 
> > Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> 
> Context are yet another thing that will nicely fragment our global gtt
> space. You don't pin them to mappable, which is a start, but I wonder
> whether we should integrate this into our evict_something code? Although
> that project is more involved with the current evict code, so maybe just
> add a fixme.

My suggestion for when we want to step beyond having the context pinned
all the time was for a hook into unbind that checked to see if this was
a "pinned" object and to fixup any registers to point back to the
default. In the case of contexts, it would check a flag to see if it was
indeed the active context and then schedule a change back to the default
context prior to unbinding. From another viewpoint, this sounds alot
like fences, and maybe we should add the tracking to the CXTID register
in a similar manner.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre