[Intel-gfx] [PATCH 06/53] drm/i915/bdw: Introduce one context backing object per engine

[oscar.mateo at intel.com]

From: Oscar Mateo <oscar.mateo at intel.com>

A context backing object only makes sense for a given engine (because
it holds state data specific to that engine).

In legacy ringbuffer sumission mode, the only MI_SET_CONTEXT we really
perform is for the render engine, so one backing object is all we needed.

With Execlists, however, we need backing objects for every engine, as
contexts become the only way to submit workloads to the GPU. To tackle
this problem, we multiplex the context struct to contain <no-of-engines>
objects.

Originally, I colored this code by instantiating one new context for
every engine I wanted to use, but this change suggested by Brad Volkin
makes it more elegant.

v2: Leave the old backing object pointer behind. Daniel Vetter suggested
using a union, but it makes more sense to keep render_obj as a NULL
pointer behind, to make sure no one uses it incorrectly when Execlists
are enabled, similar to what we are doing with ring->buffer (Rusty's API
level 5).

Signed-off-by: Oscar Mateo <oscar.mateo at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index a15370c..ccc1ba6 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -593,7 +593,14 @@ struct intel_context {
 	uint8_t remap_slice;
 	struct drm_i915_file_private *file_priv;
 	struct intel_engine_cs *last_ring;
+
+	/* Legacy ring buffer submission */
 	struct drm_i915_gem_object *render_obj;
+	/* Execlists */
+	struct {
+		struct drm_i915_gem_object *obj;
+	} engine[I915_NUM_RINGS];
+
 	struct i915_ctx_hang_stats hang_stats;
 	struct i915_address_space *vm;
 
-- 
1.9.0