drm/i915: Reorganize intel_enable_ppgtt

This patch consolidates the way in which we handle the various supported
PPGTT by module parameter in addition to what the hardware supports. It
strives to make doing the right thing in the code as simple as possible,
with the USES_ macros.

I've opted to add the full PPGTT argument simply so one can see how I
intend to use this function. It will not/cannot be used until later.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index fdeed68..c69fa2c 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -888,8 +888,7 @@
 	return ret;
 }
 
-static int i915_gem_init_ppgtt(struct drm_device *dev,
-			       struct i915_hw_ppgtt *ppgtt)
+int i915_gem_init_ppgtt(struct drm_device *dev, struct i915_hw_ppgtt *ppgtt)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret = 0;
@@ -1397,21 +1396,6 @@
 	ggtt_vm->clear_range(ggtt_vm, end / PAGE_SIZE - 1, 1, true);
 }
 
-static bool
-intel_enable_ppgtt(struct drm_device *dev)
-{
-	if (i915_enable_ppgtt >= 0)
-		return i915_enable_ppgtt;
-
-#ifdef CONFIG_INTEL_IOMMU
-	/* Disable ppgtt on SNB if VT-d is on. */
-	if (INTEL_INFO(dev)->gen == 6 && intel_iommu_gfx_mapped)
-		return false;
-#endif
-
-	return true;
-}
-
 void i915_gem_init_global_gtt(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -1421,7 +1405,7 @@
 	mappable_size = dev_priv->gtt.mappable_end;
 
 	i915_gem_setup_global_gtt(dev, 0, mappable_size, gtt_size);
-	if (intel_enable_ppgtt(dev) && HAS_ALIASING_PPGTT(dev)) {
+	if (USES_ALIASING_PPGTT(dev)) {
 		struct i915_hw_ppgtt *ppgtt;
 		int ret;