drm/i915/perf: Schedule oa_config after modifying the contexts

We wish that the scheduler emit the context modification commands prior
to enabling the oa_config, for which we must explicitly inform it of the
ordering constraints. This is especially important as we now wait for
the final oa_config setup to be completed and as this wait may be on a
distinct context to the state modifications, we need that command packet
to be always last in the queue.

We borrow the i915_active for its ability to track multiple timelines
and the last dma_fence on each; a flexible dma_resv. Keeping track of
each dma_fence is important for us so that we can efficiently schedule
the requests and reprioritise as required.
Reported-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200327112212.16046-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_perf_types.h

@@ -22,6 +22,7 @@
 
 struct drm_i915_private;
 struct file;
+struct i915_active;
 struct i915_gem_context;
 struct i915_perf;
 struct i915_vma;
@@ -340,8 +341,8 @@ struct i915_oa_ops {
 	 * counter reports being sampled. May apply system constraints such as
 	 * disabling EU clock gating as required.
 	 */
-	struct i915_request *
-		(*enable_metric_set)(struct i915_perf_stream *stream);
+	int (*enable_metric_set)(struct i915_perf_stream *stream,
+				 struct i915_active *active);
 
 	/**
 	 * @disable_metric_set: Remove system constraints associated with using