[Intel-gfx] [PATCH 2/6] 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/i915_reg.h         |  1 +
 drivers/gpu/drm/i915/intel_ringbuffer.c | 54 +++++++++++++++++++++------------
 drivers/gpu/drm/i915/intel_ringbuffer.h |  1 +
 3 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 393f93ecd41a..6dd35f849781 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -915,6 +915,7 @@ enum punit_power_well {
 # define MI_FLUSH_ENABLE				(1 << 12)
 # define ASYNC_FLIP_PERF_DISABLE			(1 << 14)
 # define MODE_IDLE					(1 << 9)
+# define STOP_RING					(1 << 8)
 
 #define GEN6_GT_MODE	0x20d0
 #define GEN7_GT_MODE	0x7008
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 475391ce671a..98ba7d594718 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -439,32 +439,41 @@ 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;
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	struct drm_i915_gem_object *obj = ring->obj;
-	int ret = 0;
-	u32 head;
+	struct drm_i915_private *dev_priv = to_i915(ring->dev);
 
-	gen6_gt_force_wake_get(dev_priv, FORCEWAKE_ALL);
+	if (!IS_GEN2(ring->dev)) {
+		I915_WRITE_MODE(ring, _MASKED_BIT_ENABLE(STOP_RING));
+		if (wait_for_atomic((I915_READ_MODE(ring) & MODE_IDLE) != 0, 1000)) {
+			DRM_ERROR("%s :timed out trying to stop ring\n", ring->name);
+			return false;
+		}
+	}
 
-	/* 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);
+	if (!IS_GEN2(ring->dev)) {
+		(void)I915_READ_CTL(ring);
+		I915_WRITE_MODE(ring, _MASKED_BIT_DISABLE(STOP_RING));
+	}
 
-	head = I915_READ_HEAD(ring) & HEAD_ADDR;
+	return (I915_READ_HEAD(ring) & HEAD_ADDR) == 0;
+}
 
-	/* G45 ring initialization fails to reset head to zero */
-	if (head != 0) {
+static int init_ring_common(struct intel_ring_buffer *ring)
+{
+	struct drm_device *dev = ring->dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct drm_i915_gem_object *obj = ring->obj;
+	int ret = 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,
@@ -473,9 +482,7 @@ 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,
@@ -483,9 +490,16 @@ static int init_ring_common(struct intel_ring_buffer *ring)
 				  I915_READ_HEAD(ring),
 				  I915_READ_TAIL(ring),
 				  I915_READ_START(ring));
+			ret = -EIO;
+			goto out;
 		}
 	}
 
+	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
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 270a6a973438..2b91c4b4d34b 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -34,6 +34,7 @@ struct  intel_hw_status_page {
 #define I915_WRITE_IMR(ring, val) I915_WRITE(RING_IMR((ring)->mmio_base), val)
 
 #define I915_READ_MODE(ring) I915_READ(RING_MI_MODE((ring)->mmio_base))
+#define I915_WRITE_MODE(ring, val) I915_WRITE(RING_MI_MODE((ring)->mmio_base), val)
 
 enum intel_ring_hangcheck_action {
 	HANGCHECK_IDLE = 0,
-- 
1.9.1