[Intel-gfx] [PATCH v3 12/34] drm/i915: Split context enabling from init

[Ben Widawsky]

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)

Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_drv.h         |  1 +
 drivers/gpu/drm/i915/i915_gem.c         | 15 ++++++++++++---
 drivers/gpu/drm/i915/i915_gem_context.c | 23 ++++++++++++-----------
 3 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index d6dd26a..f1b59b1 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1715,6 +1715,7 @@ struct dma_buf *i915_gem_prime_export(struct drm_device *dev,
 /* i915_gem_context.c */
 void i915_gem_context_init(struct drm_device *dev);
 void i915_gem_context_fini(struct drm_device *dev);
+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);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 6d0d302..674154f 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4036,10 +4036,17 @@ i915_gem_init_hw(struct drm_device *dev)
 		return ret;
 
 	/*
-	 * 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.
 	 */
-	i915_gem_context_init(dev);
+	if (i915_gem_context_enable(dev_priv)) {
+		i915_gem_context_fini(dev);
+		dev_priv->hw_contexts_disabled = true;
+	}
+
 	if (dev_priv->mm.aliasing_ppgtt) {
 		ret = dev_priv->mm.aliasing_ppgtt->enable(dev);
 		if (ret) {
@@ -4067,6 +4074,8 @@ int i915_gem_init(struct drm_device *dev)
 
 	i915_gem_init_global_gtt(dev);
 
+	i915_gem_context_init(dev);
+
 	ret = i915_gem_init_hw(dev);
 	mutex_unlock(&dev->struct_mutex);
 	if (ret) {
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 9ce0acd..22f90c7 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -219,19 +219,11 @@ static int create_default_context(struct drm_i915_private *dev_priv)
 		goto err_destroy;
 	}
 
-	ret = do_switch(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_unpin(ctx->obj);
 err_destroy:
 	i915_gem_context_unreference(ctx);
 	return ret;
@@ -247,9 +239,10 @@ void i915_gem_context_init(struct drm_device *dev)
 		return;
 	}
 
-	/* If called from reset, or thaw... we've been here already */
-	if (dev_priv->hw_contexts_disabled ||
-	    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->hw_contexts_disabled ||
+	    WARN_ON(dev_priv->ring[RCS].default_context)))
 		return;
 
 	dev_priv->hw_context_size = round_up(get_context_size(dev), 4096);
@@ -302,6 +295,14 @@ void i915_gem_context_fini(struct drm_device *dev)
 	dev_priv->ring[RCS].last_context = NULL;
 }
 
+int i915_gem_context_enable(struct drm_i915_private *dev_priv)
+{
+	if (dev_priv->hw_contexts_disabled)
+		return 0;
+	BUG_ON(!dev_priv->ring[RCS].default_context);
+	return do_switch(dev_priv->ring[RCS].default_context);
+}
+
 static int context_idr_cleanup(int id, void *p, void *data)
 {
 	struct i915_hw_context *ctx = p;
-- 
1.8.2.3