drm/i915: Simplify i915_gem_release_all_mmaps()

An object can only have an active gtt mapping if it is currently bound
into the global gtt. Therefore we can simply walk the list of all bound
objects and check the flag upon those for an active gtt mapping.

From commit 48018a57a8f5900e7e53ffaa0adeb784095accfb
Author: Paulo Zanoni <paulo.r.zanoni@intel.com>
Date:   Fri Dec 13 15:22:31 2013 -0200

    drm/i915: release the GTT mmaps when going into D3

Also note that the WARN is inappropriate for this function as GPU
activity is orthogonal to GTT mmap status. Rather it is the caller that
relies upon this condition and so it should assert that the GPU is idle
itself.

References: https://bugs.freedesktop.org/show_bug.cgi?id=80081
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Tested-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem.c

@@ -1632,22 +1632,6 @@ out:
 	return ret;
 }
 
-void i915_gem_release_all_mmaps(struct drm_i915_private *dev_priv)
-{
-	struct i915_vma *vma;
-
-	/*
-	 * Only the global gtt is relevant for gtt memory mappings, so restrict
-	 * list traversal to objects bound into the global address space. Note
-	 * that the active list should be empty, but better safe than sorry.
-	 */
-	WARN_ON(!list_empty(&dev_priv->gtt.base.active_list));
-	list_for_each_entry(vma, &dev_priv->gtt.base.active_list, mm_list)
-		i915_gem_release_mmap(vma->obj);
-	list_for_each_entry(vma, &dev_priv->gtt.base.inactive_list, mm_list)
-		i915_gem_release_mmap(vma->obj);
-}
-
 /**
  * i915_gem_release_mmap - remove physical page mappings
  * @obj: obj in question
@@ -1673,6 +1657,15 @@ i915_gem_release_mmap(struct drm_i915_gem_object *obj)
 	obj->fault_mappable = false;
 }
 
+void
+i915_gem_release_all_mmaps(struct drm_i915_private *dev_priv)
+{
+	struct drm_i915_gem_object *obj;
+
+	list_for_each_entry(obj, &dev_priv->mm.bound_list, global_list)
+		i915_gem_release_mmap(obj);
+}
+
 uint32_t
 i915_gem_get_gtt_size(struct drm_device *dev, uint32_t size, int tiling_mode)
 {