drm/i915: abolish separate per-ring default_context pointers

Now that we've eliminated a lot of uses of ring->default_context,
we can eliminate the pointer itself.

All the engines share the same default intel_context, so we can just
keep a single reference to it in the dev_priv structure rather than one
in each of the engine[] elements. This make refcounting more sensible
too, as we now have a refcount of one for the one pointer, rather than
a refcount of one but multiple pointers.

From an idea by Chris Wilson.

v2:	transform an extra instance of ring->default_context introduced by
    42f1cae8c drm/i915: Restore inhibiting the load of the default context
    That patch's commentary includes:
	v2: Mark the global default context as uninitialized on GPU reset so
	    that the context-local workarounds are reloaded upon re-enabling
    The code implementing that now also benefits from the replacement of
    the multiple (per-ring) pointers to the default context with a single
    pointer to the unique kernel context.

v4:	Rebased, remove underused local (Nick Hoath)

Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Reviewed-by: Nick Hoath <nicholas.hoath@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1453230175-19330-3-git-send-email-david.s.gordon@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 8e716b6..06abe1b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2680,7 +2680,7 @@ void i915_gem_request_free(struct kref *req_ref)
 
 	if (ctx) {
 		if (i915.enable_execlists) {
-			if (ctx != req->ring->default_context)
+			if (ctx != req->i915->kernel_context)
 				intel_lr_context_unpin(req);
 		}
 
@@ -2776,7 +2776,7 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
 	int err;
 
 	if (ctx == NULL)
-		ctx = engine->default_context;
+		ctx = to_i915(engine->dev)->kernel_context;
 	err = __i915_gem_request_alloc(engine, ctx, &req);
 	return err ? ERR_PTR(err) : req;
 }
@@ -4864,7 +4864,7 @@ i915_gem_init_hw(struct drm_device *dev)
 	 */
 	init_unused_rings(dev);
 
-	BUG_ON(!dev_priv->ring[RCS].default_context);
+	BUG_ON(!dev_priv->kernel_context);
 
 	ret = i915_ppgtt_init_hw(dev);
 	if (ret) {