[Intel-gfx] [PATCH] drm/i915: Move all ring resets before setting the HWS page

[Chris Wilson]

In commit a51435a3137ad8ae75c288c39bd2d8b2696bae8f
Author: Naresh Kumar Kachhi <naresh.kumar.kachhi at intel.com>
Date:   Wed Mar 12 16:39:40 2014 +0530

    drm/i915: disable rings before HW status page setup

we reordered stopping the rings to do so before we set the HWS register.
However, there is an extra workaround for g45 to reset the rings twice,
and for consistency we should apply that workaround before setting the
HWS to be sure that the rings are truly stopped.

Cc: Naresh Kumar Kachhi <naresh.kumar.kachhi at intel.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c | 40 ++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index ce8ddee2e77e..99b1d8e15711 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -444,32 +444,30 @@ static void ring_setup_phys_status_page(struct intel_ring_buffer *ring)
 	I915_WRITE(HWS_PGA, addr);
 }
 
-static int init_ring_common(struct intel_ring_buffer *ring)
+static bool stop_ring(struct intel_ring_buffer *ring)
 {
-	struct drm_device *dev = ring->dev;
-	drm_i915_private_t *dev_priv = dev->dev_private;
-	struct drm_i915_gem_object *obj = ring->obj;
-	int ret = 0;
-	u32 head;
-
-	gen6_gt_force_wake_get(dev_priv, FORCEWAKE_ALL);
+	drm_i915_private_t *dev_priv = to_i915(ring->dev);
 
-	/* Stop the ring if it's running. */
 	I915_WRITE_CTL(ring, 0);
 	I915_WRITE_HEAD(ring, 0);
 	ring->write_tail(ring, 0);
 	if (wait_for_atomic((I915_READ_MODE(ring) & MODE_IDLE) != 0, 1000))
 		DRM_ERROR("%s :timed out trying to stop ring\n", ring->name);
 
-	if (I915_NEED_GFX_HWS(dev))
-		intel_ring_setup_status_page(ring);
-	else
-		ring_setup_phys_status_page(ring);
+	return I915_READ_HEAD(ring) & HEAD_ADDR;
+}
 
-	head = I915_READ_HEAD(ring) & HEAD_ADDR;
+static int init_ring_common(struct intel_ring_buffer *ring)
+{
+	struct drm_device *dev = ring->dev;
+	drm_i915_private_t *dev_priv = dev->dev_private;
+	struct drm_i915_gem_object *obj = ring->obj;
+	int ret = 0;
 
-	/* G45 ring initialization fails to reset head to zero */
-	if (head != 0) {
+	gen6_gt_force_wake_get(dev_priv, FORCEWAKE_ALL);
+
+	if (stop_ring(ring)) {
+		/* G45 ring initialization often fails to reset head to zero */
 		DRM_DEBUG_KMS("%s head not reset to zero "
 			      "ctl %08x head %08x tail %08x start %08x\n",
 			      ring->name,
@@ -478,9 +476,7 @@ static int init_ring_common(struct intel_ring_buffer *ring)
 			      I915_READ_TAIL(ring),
 			      I915_READ_START(ring));
 
-		I915_WRITE_HEAD(ring, 0);
-
-		if (I915_READ_HEAD(ring) & HEAD_ADDR) {
+		if (stop_ring(ring))
 			DRM_ERROR("failed to set %s head to zero "
 				  "ctl %08x head %08x tail %08x start %08x\n",
 				  ring->name,
@@ -488,9 +484,13 @@ static int init_ring_common(struct intel_ring_buffer *ring)
 				  I915_READ_HEAD(ring),
 				  I915_READ_TAIL(ring),
 				  I915_READ_START(ring));
-		}
 	}
 
+	if (I915_NEED_GFX_HWS(dev))
+		intel_ring_setup_status_page(ring);
+	else
+		ring_setup_phys_status_page(ring);
+
 	/* Initialize the ring. This must happen _after_ we've cleared the ring
 	 * registers with the above sequence (the readback of the HEAD registers
 	 * also enforces ordering), otherwise the hw might lose the new ring
-- 
1.9.1