[Intel-gfx] [PATCH 1/2] drm/i915: Eliminate unrequired dwords for MI_SET_CONTEXT

[Chris Wilson]

A later patch adds yet another workaround for MI_SET_CONTEXT, at which
point we start to end up with more NOOPs than actual command dwords
along the non-workaround paths. It is time that we made the MI_SET_CONTEXT
a variable length block and only emit the dwords we truly need.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 879bfa2..8a7b61e 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -348,7 +348,7 @@ mi_set_context(struct intel_ring_buffer *ring,
 	       struct i915_hw_context *new_context,
 	       u32 hw_flags)
 {
-	int ret;
+	int ret, len;
 
 	/* w/a: If Flush TLB Invalidation Mode is enabled, driver must do a TLB
 	 * invalidation prior to MI_SET_CONTEXT. On GEN6 we don't set the value
@@ -361,7 +361,14 @@ mi_set_context(struct intel_ring_buffer *ring,
 			return ret;
 	}
 
-	ret = intel_ring_begin(ring, 6);
+	len = 4;
+	switch (INTEL_INFO(ring->dev)->gen) {
+	case 7:
+	case 5: len += 2;
+		break;
+	}
+
+	ret = intel_ring_begin(ring, len);
 	if (ret)
 		return ret;
 
@@ -373,9 +380,6 @@ mi_set_context(struct intel_ring_buffer *ring,
 	case 5:
 		intel_ring_emit(ring, MI_SUSPEND_FLUSH | MI_SUSPEND_FLUSH_EN);
 		break;
-	default:
-		intel_ring_emit(ring, MI_NOOP);
-		break;
 	}
 
 	intel_ring_emit(ring, MI_NOOP);
@@ -395,9 +399,6 @@ mi_set_context(struct intel_ring_buffer *ring,
 	case 5:
 		intel_ring_emit(ring, MI_SUSPEND_FLUSH);
 		break;
-	default:
-		intel_ring_emit(ring, MI_NOOP);
-		break;
 	}
 
 	intel_ring_advance(ring);
-- 
1.8.4.rc1