drm/i915: Allow the application to choose the constant addressing mode

The relative-to-general state default is useless as it means having to
rewrite the streaming kernels for each batch. Relative-to-surface is
more useful, as that stream usually needs to be rewritten for each
batch. And absolute addressing mode, vital if you start streaming
state, is also only available by adjusting the register...

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

4 files changed, 40 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 3f7b203..18746e6 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -778,6 +778,9 @@ static int i915_getparam(struct drm_device *dev, void *data,
 	case I915_PARAM_HAS_COHERENT_RINGS:
 		value = 1;
 		break;
+	case I915_PARAM_HAS_EXEC_CONSTANTS:
+		value = INTEL_INFO(dev)->gen >= 4;
+		break;
 	default:
 		DRM_DEBUG_DRIVER("Unknown parameter %d\n",
 				 param->param);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 2a653cc..aac1bf3 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -258,6 +258,7 @@ typedef struct drm_i915_private {
 	const struct intel_device_info *info;
 
 	int has_gem;
+	int relative_constants_mode;
 
 	void __iomem *regs;
 
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 5a0fbe5..c79c0b6 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3735,6 +3735,8 @@ i915_gem_load(struct drm_device *dev)
 		}
 	}
 
+	dev_priv->relative_constants_mode = I915_EXEC_CONSTANTS_REL_GENERAL;
+
 	/* Old X drivers will take 0-2 for front, back, depth buffers */
 	if (!drm_core_check_feature(dev, DRIVER_MODESET))
 		dev_priv->fence_reg_start = 3;
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index fda0dc8..61129e6 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -957,7 +957,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	struct intel_ring_buffer *ring;
 	u32 exec_start, exec_len;
 	u32 seqno;
-	int ret, i;
+	int ret, mode, i;
 
 	if (!i915_gem_check_execbuffer(args)) {
 		DRM_ERROR("execbuf with invalid offset/length\n");
@@ -997,6 +997,39 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 		return -EINVAL;
 	}
 
+	mode = args->flags & I915_EXEC_CONSTANTS_MASK;
+	switch (mode) {
+	case I915_EXEC_CONSTANTS_REL_GENERAL:
+	case I915_EXEC_CONSTANTS_ABSOLUTE:
+	case I915_EXEC_CONSTANTS_REL_SURFACE:
+		if (ring == &dev_priv->ring[RCS] &&
+		    mode != dev_priv->relative_constants_mode) {
+			if (INTEL_INFO(dev)->gen < 4)
+				return -EINVAL;
+
+			if (INTEL_INFO(dev)->gen > 5 &&
+			    mode == I915_EXEC_CONSTANTS_REL_SURFACE)
+				return -EINVAL;
+
+			ret = intel_ring_begin(ring, 4);
+			if (ret)
+				return ret;
+
+			intel_ring_emit(ring, MI_NOOP);
+			intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(1));
+			intel_ring_emit(ring, INSTPM);
+			intel_ring_emit(ring,
+					I915_EXEC_CONSTANTS_MASK << 16 | mode);
+			intel_ring_advance(ring);
+
+			dev_priv->relative_constants_mode = mode;
+		}
+		break;
+	default:
+		DRM_ERROR("execbuf with unknown constants: %d\n", mode);
+		return -EINVAL;
+	}
+
 	if (args->buffer_count < 1) {
 		DRM_ERROR("execbuf with %d buffers\n", args->buffer_count);
 		return -EINVAL;