[RFC] [PATCH 7/8] drm/i915/context: context switch implementation

[Ben Widawsky <bwidawsk@gmail.com>]

Once again, split out mostly for review...

Implementation of the context switch code (MI_SET_CONTEXT), which is
supposed to be per ringbuffer. There is a bit of ugliness for the
initial default context load, for which I had no better solution.

Slightly modified the default context creation code to check for the
previously mentioned ugliness.
---
 drivers/gpu/drm/i915/i915_context.c     |   28 ++++++---
 drivers/gpu/drm/i915/i915_drv.h         |    1 +
 drivers/gpu/drm/i915/intel_ringbuffer.c |   97 +++++++++++++++++++++++++++++++
 3 files changed, 117 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_context.c b/drivers/gpu/drm/i915/i915_context.c
index 2e38fa8..3719a87 100644
--- a/drivers/gpu/drm/i915/i915_context.c
+++ b/drivers/gpu/drm/i915/i915_context.c
@@ -123,28 +123,34 @@ static int context_init(struct drm_i915_gem_context *ctx,
 		 */
 		last = ring->context_switch(ring, ctx, 0,
 					    I915_CONTEXT_SAVE_ONLY);
-		if (!last) {
-			ret = EIO;
+		if (last != ctx) {
+			DRM_ERROR("Context switch state invalid");
+			ret = -EIO;
 			goto err_out;
 		}
 		last = ring->context_switch(ring, ctx, 0,
 					    I915_CONTEXT_SAVE_ONLY |
 					    I915_CONTEXT_FORCED_SWITCH);
-		if (!last) {
-			ret = EIO;
+		if (last != ctx) {
+			DRM_ERROR("First context switch fail");
+			ret = -EIO;
 			goto err_out;
 		}
 		last = ring->context_switch(ring, ctx, 0,
 					    I915_CONTEXT_NORMAL_SWITCH |
 					    I915_CONTEXT_FORCED_SWITCH);
+		if (last != ctx) {
+			DRM_ERROR("Final context switch fail");
+			ret = -EIO;
+			goto err_out;
+		}
 	} else {
 		last = ring->context_switch(ring, ctx, 0,
 					    I915_CONTEXT_SAVE_ONLY);
-	}
-
-	if (!last) {
-		ret = EIO;
-		goto err_out;
+		if (!last) {
+			ret = -EIO;
+			goto err_out;
+		}
 	}
 
 	if (!last->is_default)
@@ -346,7 +352,11 @@ void i915_context_load(struct drm_device *dev)
 	ret = logical_context_alloc(dev, NULL, 0, &dev_priv->default_context);
 	if (ret)
 		dev_priv->contexts_disabled = true;
+	else {
+		DRM_DEBUG_DRIVER("HW context support initialized\n");
+	}
 	mutex_unlock(&dev->struct_mutex);
+
 }
 
 void i915_context_unload(struct drm_device *dev)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 98ccbd9..39669ff 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -909,6 +909,7 @@ struct drm_i915_gem_context {
 	uint8_t ring_enable;
 	struct drm_i915_gem_object *obj;
 	bool is_default;
+	bool is_initialized;
 
 	struct drm_gem_object **bufs;
 	int slot_count;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 789c478..7d18c07 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -734,6 +734,102 @@ render_ring_dispatch_execbuffer(struct intel_ring_buffer *ring,
 	return 0;
 }
 
+static int do_ring_switch(struct intel_ring_buffer *ring,
+			  struct drm_i915_gem_context *new_context,
+			  u32 hw_flags)
+{
+	struct drm_device *dev = ring->dev;
+	int ret = 0;
+
+	if (!new_context->is_initialized) {
+		ret = intel_ring_begin(ring, 6);
+		if (ret)
+			return ret;
+		intel_ring_emit(ring, MI_NOOP | (1 << 22) | new_context->id);
+		intel_ring_emit(ring, MI_FLUSH);
+	} else {
+		ret = intel_ring_begin(ring, 4);
+		if (ret)
+			return ret;
+	}
+
+	DRM_DEBUG_DRIVER("Context switch %d -> %d\n",
+			 ring->last_context ? ring->last_context->id : -1,
+			 new_context->id);
+
+	if (IS_IRONLAKE_D(dev) || IS_IRONLAKE_M(dev))
+		intel_ring_emit(ring, MI_SUSPEND_FLUSH | MI_SUSPEND_FLUSH_EN);
+	else
+		intel_ring_emit(ring, MI_NOOP);
+
+	intel_ring_emit(ring, MI_SET_CONTEXT);
+	intel_ring_emit(ring, new_context->obj->gtt_offset |
+			MI_MM_SPACE_GTT |
+			MI_SAVE_EXT_STATE_EN |
+			MI_RESTORE_EXT_STATE_EN |
+			hw_flags);
+
+	if (IS_IRONLAKE_D(dev) || IS_IRONLAKE_M(dev))
+		intel_ring_emit(ring, MI_SUSPEND_FLUSH);
+		/* TODO: we may need a NOOP here */
+	else
+		intel_ring_emit(ring, MI_NOOP);
+
+	intel_ring_advance(ring);
+
+	return ret;
+
+}
+
+static struct drm_i915_gem_context *
+render_ring_context_switch(struct intel_ring_buffer *ring,
+			   struct drm_i915_gem_context *new_context,
+			   u32 seqno, u32 flags)
+{
+	struct drm_device *dev = ring->dev;
+	bool force = (flags & I915_CONTEXT_FORCED_SWITCH) ? true : false;
+	struct drm_i915_gem_context *last = NULL;
+	uint32_t hw_flags = 0;
+
+	if (WARN_ON(new_context->obj->gtt_offset == 0))
+		return NULL;
+
+	/* last_context is only protected by struct_mutex */
+	WARN_ON(!mutex_is_locked(&dev->struct_mutex));
+
+	if (!force && (ring->last_context == new_context))  {
+		if (WARN_ON(seqno == 0))
+			seqno = ring->get_seqno(ring);
+
+		if (!new_context->is_default)
+			i915_gem_object_move_to_active(new_context->obj,
+						       ring, seqno);
+		return new_context;
+	}
+
+	if (flags & I915_CONTEXT_SAVE_ONLY)
+		hw_flags = MI_RESTORE_INHIBIT;
+
+	if (do_ring_switch(ring, new_context, hw_flags))
+		return NULL;
+
+	last = ring->last_context;
+	ring->last_context = new_context;
+
+	if (last && !last->is_default)
+		i915_gem_object_move_to_active(last->obj, ring, seqno);
+
+	/* XXX The first call to this default and last are NULL. Unfortunately
+	 * the only mechanism we have to determine failure is */
+	if (!new_context->is_initialized && !last) {
+		WARN_ON(!new_context->is_default);
+		last = new_context;
+	} else
+		new_context->is_initialized = true;
+
+	return last;
+}
+
 static void cleanup_status_page(struct intel_ring_buffer *ring)
 {
 	drm_i915_private_t *dev_priv = ring->dev->dev_private;
@@ -1008,6 +1104,7 @@ static const struct intel_ring_buffer render_ring = {
 	.irq_put		= render_ring_put_irq,
 	.dispatch_execbuffer	= render_ring_dispatch_execbuffer,
        .cleanup			= render_ring_cleanup,
+	.context_switch		= render_ring_context_switch,
 };
 
 /* ring buffer for bit-stream decoder */
-- 
1.7.3.4