[Intel-gfx] [PATCH 1/2] drm/i915: Don't set a MBZ bit in gen2 MI_FLUSH

[Chris Wilson]

On gen2, MI_EXE_FLUSH is actually an AGP flush bit and is documented as
being must-be-zero. So obey the documentation, and separate the gen2
flush into its own little routine.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c |   30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 8e632a5..9b89d4a 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -53,6 +53,32 @@ static inline int ring_space(struct intel_ring_buffer *ring)
 }
 
 static int
+gen2_render_ring_flush(struct intel_ring_buffer *ring,
+		       u32	invalidate_domains,
+		       u32	flush_domains)
+{
+	u32 cmd;
+	int ret;
+
+	cmd = MI_FLUSH;
+	if ((flush_domains & I915_GEM_DOMAIN_RENDER) == 0)
+		cmd |= MI_NO_WRITE_FLUSH;
+
+	if (invalidate_domains & I915_GEM_DOMAIN_SAMPLER)
+		cmd |= MI_READ_FLUSH;
+
+	ret = intel_ring_begin(ring, 2);
+	if (ret)
+		return ret;
+
+	intel_ring_emit(ring, cmd);
+	intel_ring_emit(ring, MI_NOOP);
+	intel_ring_advance(ring);
+
+	return 0;
+}
+
+static int
 render_ring_flush(struct intel_ring_buffer *ring,
 		  u32	invalidate_domains,
 		  u32	flush_domains)
@@ -1296,6 +1322,8 @@ int intel_init_render_ring_buffer(struct drm_device *dev)
 	} else {
 		ring->add_request = i9xx_add_request;
 		ring->flush = render_ring_flush;
+		if (INTEL_INFO(dev)->gen == 2)
+			ring->flush = gen2_render_ring_flush;
 		ring->get_seqno = ring_get_seqno;
 		ring->irq_get = i9xx_ring_get_irq;
 		ring->irq_put = i9xx_ring_put_irq;
@@ -1341,6 +1369,8 @@ int intel_render_ring_init_dri(struct drm_device *dev, u64 start, u32 size)
 	 * the special gen5 functions. */
 	ring->add_request = i9xx_add_request;
 	ring->flush = render_ring_flush;
+	if (INTEL_INFO(dev)->gen == 2)
+		ring->flush = gen2_render_ring_flush;
 	ring->get_seqno = ring_get_seqno;
 	ring->irq_get = i9xx_ring_get_irq;
 	ring->irq_put = i9xx_ring_put_irq;
-- 
1.7.10