[PATCH 14/15] drm/i915: Factor out and expose i915_steal_fence()

[Zhi Wang <zhi.a.wang@intel.com>]

Factor out and expose fence stealing functionality for GVT-g. GVT-g
will use i915_find_fence_reg() to find a free/unpin fence register
and use i915_steal_fence() to steal it.

Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h       |  1 +
 drivers/gpu/drm/i915/i915_gem_fence.c | 39 +++++++++++++++++++++++++++--------
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index ae1149c..96d9abd 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3376,6 +3376,7 @@ i915_gem_object_ggtt_unpin(struct drm_i915_gem_object *obj)
 /* i915_gem_fence.c */
 int __must_check i915_gem_object_get_fence(struct drm_i915_gem_object *obj);
 int __must_check i915_gem_object_put_fence(struct drm_i915_gem_object *obj);
+int i915_steal_fence(struct drm_i915_fence_reg *reg);
 
 bool i915_gem_object_pin_fence(struct drm_i915_gem_object *obj);
 void i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj);
diff --git a/drivers/gpu/drm/i915/i915_gem_fence.c b/drivers/gpu/drm/i915/i915_gem_fence.c
index a2b938e..e790d7b 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence.c
@@ -346,6 +346,33 @@ deadlock:
 }
 
 /**
+ * i915_steal_fence - steal a fence from a GEM object
+ * @reg: the fence register to be stolen
+ *
+ * Returns:
+ *
+ * 0 on success, negative error code on failure.
+ */
+int i915_steal_fence(struct drm_i915_fence_reg *reg)
+{
+	int ret;
+
+	if (WARN_ON(reg->pin_count))
+		return -EBUSY;
+
+	if (reg->obj) {
+		struct drm_i915_gem_object *old = reg->obj;
+
+		ret = i915_gem_object_wait_fence(old);
+		if (ret)
+			return ret;
+
+		i915_gem_object_fence_lost(old);
+	}
+	return 0;
+}
+
+/**
  * i915_gem_object_get_fence - set up fencing for an object
  * @obj: object to map through a fence reg
  *
@@ -397,15 +424,9 @@ i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
 		if (IS_ERR(reg))
 			return PTR_ERR(reg);
 
-		if (reg->obj) {
-			struct drm_i915_gem_object *old = reg->obj;
-
-			ret = i915_gem_object_wait_fence(old);
-			if (ret)
-				return ret;
-
-			i915_gem_object_fence_lost(old);
-		}
+		ret = i915_steal_fence(reg);
+		if (ret)
+			return ret;
 	} else
 		return 0;
 
-- 
1.9.1

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