drm/i915: Convert i915_semaphores_is_enabled over to early sanitize

Rather than recomputing whether semaphores are enabled, we can do that
computation once during early initialisation as the i915.semaphores
module parameter is now read-only.

s/i915_semaphores_is_enabled/i915.semaphores/

v2: Add the state to the debug dmesg as well

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1469005202-9659-10-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469017917-15134-9-git-send-email-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 536acd5..40047eb 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2856,7 +2856,7 @@
 	if (i915_gem_request_completed(from_req))
 		return 0;
 
-	if (!i915_semaphore_is_enabled(to_i915(obj->base.dev))) {
+	if (!i915.semaphores) {
 		struct drm_i915_private *i915 = to_i915(obj->base.dev);
 		ret = __i915_wait_request(from_req,
 					  i915->mm.interruptible,
@@ -4537,6 +4537,27 @@
 	return ret;
 }
 
+bool intel_sanitize_semaphores(struct drm_i915_private *dev_priv, int value)
+{
+	if (INTEL_INFO(dev_priv)->gen < 6)
+		return false;
+
+	/* TODO: make semaphores and Execlists play nicely together */
+	if (i915.enable_execlists)
+		return false;
+
+	if (value >= 0)
+		return value;
+
+#ifdef CONFIG_INTEL_IOMMU
+	/* Enable semaphores on SNB when IO remapping is off */
+	if (INTEL_INFO(dev_priv)->gen == 6 && intel_iommu_gfx_mapped)
+		return false;
+#endif
+
+	return true;
+}
+
 int i915_gem_init(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);