drm/i915: Split context enabling from init

We **need** to do this for exactly 1 reason, because we want to embed a
PPGTT into the context, but we don't want to special case the default
context.

To achieve that, we must be able to initialize contexts after the GTT is
setup (so we can allocate and pin the default context's BO), but before
the PPGTT and rings are initialized. This is because, currently, context
initialization requires ring usage. We don't have rings until after the
GTT is setup. If we split the enabling part of context initialization,
the part requiring the ringbuffer, we can untangle this, and then later
embed the PPGTT

Incidentally this allows us to also adhere to the original design of
context init/fini in future patches: they were only ever meant to be
called at driver load and unload.

v2: Move hw_contexts_disabled test in i915_gem_context_enable() (Chris)

v3: BUG_ON after checking for disabled contexts. Or else it blows up pre
gen6 (Ben)

v4: Forward port
Modified enable for each ring, since that patch is earlier in the series
Dropped ring arg from create_default_context so it can be used by others
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -2227,6 +2227,7 @@ int __must_check i915_gem_context_init(struct drm_device *dev);
 void i915_gem_context_fini(struct drm_device *dev);
 void i915_gem_context_reset(struct drm_device *dev);
 int i915_gem_context_open(struct drm_device *dev, struct drm_file *file);
+int i915_gem_context_enable(struct drm_i915_private *dev_priv);
 void i915_gem_context_close(struct drm_device *dev, struct drm_file *file);
 int i915_switch_context(struct intel_ring_buffer *ring,
 			struct drm_file *file, int to_id);

drivers/gpu/drm/i915/i915_gem.c

@@ -4433,14 +4433,16 @@ i915_gem_init_hw(struct drm_device *dev)
 		i915_gem_l3_remap(&dev_priv->ring[RCS], i);
 
 	/*
-	 * XXX: There was some w/a described somewhere suggesting loading
-	 * contexts before PPGTT.
+	 * XXX: Contexts should only be initialized once. Doing a switch to the
+	 * default context switch however is something we'd like to do after
+	 * reset or thaw (the latter may not actually be necessary for HW, but
+	 * goes with our code better). Context switching requires rings (for
+	 * the do_switch), but before enabling PPGTT. So don't move this.
 	 */
-	ret = i915_gem_context_init(dev);
+	ret = i915_gem_context_enable(dev_priv);
 	if (ret) {
-		i915_gem_cleanup_ringbuffer(dev);
-		DRM_ERROR("Context initialization failed %d\n", ret);
-		return ret;
+		DRM_ERROR("Context enable failed %d\n", ret);
+		goto err_out;
 	}
 
 	if (dev_priv->mm.aliasing_ppgtt) {
@@ -4448,10 +4450,15 @@ i915_gem_init_hw(struct drm_device *dev)
 		if (ret) {
 			i915_gem_cleanup_aliasing_ppgtt(dev);
 			DRM_INFO("PPGTT enable failed. This is not fatal, but unexpected\n");
+			ret = 0;
 		}
 	}
 
 	return 0;
+
+err_out:
+	i915_gem_cleanup_ringbuffer(dev);
+	return ret;
 }
 
 int i915_gem_init(struct drm_device *dev)
@@ -4470,9 +4477,14 @@ int i915_gem_init(struct drm_device *dev)
 
 	i915_gem_init_global_gtt(dev);
 
+	ret = i915_gem_context_init(dev);
+	if (ret)
+		return ret;
+
 	ret = i915_gem_init_hw(dev);
 	mutex_unlock(&dev->struct_mutex);
 	if (ret) {
+		i915_gem_context_fini(dev);
 		i915_gem_cleanup_aliasing_ppgtt(dev);
 		drm_mm_takedown(&dev_priv->gtt.base.mm);
 		return ret;

drivers/gpu/drm/i915/i915_gem_context.c

@@ -237,19 +237,11 @@ static int create_default_context(struct drm_device *dev)
 		goto err_destroy;
 	}
 
-	ret = do_switch(&dev_priv->ring[RCS], ctx);
-	if (ret) {
-		DRM_DEBUG_DRIVER("Switch failed %d\n", ret);
-		goto err_unpin;
-	}
-
 	dev_priv->ring[RCS].default_context = ctx;
 
 	DRM_DEBUG_DRIVER("Default HW context loaded\n");
 	return 0;
 
-err_unpin:
-	i915_gem_object_ggtt_unpin(ctx->obj);
 err_destroy:
 	i915_gem_context_unreference(ctx);
 	return ret;
@@ -307,8 +299,9 @@ int i915_gem_context_init(struct drm_device *dev)
 	if (!HAS_HW_CONTEXTS(dev))
 		return 0;
 
-	/* If called from reset, or thaw... we've been here already */
-	if (dev_priv->ring[RCS].default_context)
+	/* Init should only be called once per module load. Eventually the
+	 * restriction on the context_disabled check can be loosened. */
+	if (WARN_ON(dev_priv->ring[RCS].default_context))
 		return 0;
 
 	dev_priv->hw_context_size = round_up(get_context_size(dev), 4096);
@@ -384,6 +377,28 @@ void i915_gem_context_fini(struct drm_device *dev)
 	i915_gem_context_unreference(dctx);
 }
 
+int i915_gem_context_enable(struct drm_i915_private *dev_priv)
+{
+	struct intel_ring_buffer *ring;
+	int ret, i;
+
+	if (!HAS_HW_CONTEXTS(dev_priv->dev))
+		return 0;
+
+	/* FIXME: We should make this work, even in reset */
+	if (i915_reset_in_progress(&dev_priv->gpu_error))
+		return 0;
+
+	BUG_ON(!dev_priv->ring[RCS].default_context);
+	for_each_ring(ring, dev_priv, i) {
+		ret = do_switch(ring, ring->default_context);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 static int context_idr_cleanup(int id, void *p, void *data)
 {
 	struct i915_hw_context *ctx = p;