[Intel-gfx] [PATCH 3/4] drm/i915: Reorder hw init to avoid executing with invalid context/mm state

[Mika Kuoppala]

From: Chris Wilson <chris at chris-wilson.co.uk>

Currently we initialise the rings, add the first context switch to the
ring and execute our golden state then enable (aliasing or full) ppgtt.
However, as we enable ppgtt using direct MMIO but load the PD using
MI_LRI, we end up executing the context switch and golden render state
with an invalid PD generating page faults. To solve this issue, first do
the ppgtt PD setup, then set the default context and write the commands
to run the render state into the ring, before we activate the ring. This
allows us to be sure that the register state is valid before we begin
execution.

This was spotted when writing the seqno/request conversion, but only with
the ERROR capture did I realise that it was a necessity now.

RFC: cleanup the error handling in i915_gem_init_hw.

v2: added intel_ring_reset
v3: adapt to ring->start_ring

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk> (v1)
Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 8147e2e..5636351 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4856,11 +4856,25 @@ cleanup_render_ring:
 	return ret;
 }
 
+static int i915_gem_init_ring_hw(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_engine_cs *ring;
+	int i, ret;
+
+	for_each_ring(ring, dev_priv, i) {
+		ret = ring->init_hw(ring);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 int
 i915_gem_init_hw(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	struct intel_engine_cs *ring;
 	int ret, i;
 
 	if (INTEL_INFO(dev)->gen < 6 && !intel_enable_gtt())
@@ -4898,13 +4912,7 @@ i915_gem_init_hw(struct drm_device *dev)
 	 */
 	init_unused_rings(dev);
 
-	for_each_ring(ring, dev_priv, i) {
-		ret = ring->init_hw(ring);
-		if (ret)
-			goto out;
-	}
-
-	i915_gem_start_ringbuffers(dev);
+	i915_gem_init_ring_hw(dev);
 
 	for (i = 0; i < NUM_L3_SLICES(dev); i++)
 		i915_gem_l3_remap(&dev_priv->ring[RCS], i);
@@ -4915,6 +4923,9 @@ i915_gem_init_hw(struct drm_device *dev)
 		i915_gem_cleanup_ringbuffer(dev);
 	}
 
+	for (i = 0; i < NUM_L3_SLICES(dev); i++)
+		i915_gem_l3_remap(&dev_priv->ring[RCS], i);
+
 	ret = i915_gem_context_enable(dev_priv);
 	if (ret && ret != -EIO) {
 		DRM_ERROR("Context enable failed %d\n", ret);
@@ -4923,6 +4934,8 @@ i915_gem_init_hw(struct drm_device *dev)
 		goto out;
 	}
 
+	i915_gem_start_ringbuffers(dev);
+
 out:
 	intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
 	return ret;
-- 
1.9.1