drm/i915: introduce intel_has_sagv()

And use it to move knowledge about the SAGV-supporting platforms from
the callers to the SAGV code.

We'll add more platforms to intel_has_sagv(), so IMHO it makes more
sense to move all this to a single function instead of patching all
the callers every time we add SAGV support to a new platform.

v2: Move I915_SAGV_NOT_CONTROLLED to the new function (Lyude).

Cc: stable@vger.kernel.org
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1474578035-424-3-git-send-email-paulo.r.zanoni@intel.com
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 4e50d33..4210165f 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2877,6 +2877,13 @@
 	}
 }
 
+static bool
+intel_has_sagv(struct drm_i915_private *dev_priv)
+{
+	return IS_SKYLAKE(dev_priv) &&
+	       dev_priv->sagv_status != I915_SAGV_NOT_CONTROLLED;
+}
+
 /*
  * SAGV dynamically adjusts the system agent voltage and clock frequencies
  * depending on power and performance requirements. The display engine access
@@ -2893,8 +2900,10 @@
 {
 	int ret;
 
-	if (dev_priv->sagv_status == I915_SAGV_NOT_CONTROLLED ||
-	    dev_priv->sagv_status == I915_SAGV_ENABLED)
+	if (!intel_has_sagv(dev_priv))
+		return 0;
+
+	if (dev_priv->sagv_status == I915_SAGV_ENABLED)
 		return 0;
 
 	DRM_DEBUG_KMS("Enabling the SAGV\n");
@@ -2942,8 +2951,10 @@
 {
 	int ret, result;
 
-	if (dev_priv->sagv_status == I915_SAGV_NOT_CONTROLLED ||
-	    dev_priv->sagv_status == I915_SAGV_DISABLED)
+	if (!intel_has_sagv(dev_priv))
+		return 0;
+
+	if (dev_priv->sagv_status == I915_SAGV_DISABLED)
 		return 0;
 
 	DRM_DEBUG_KMS("Disabling the SAGV\n");
@@ -2984,6 +2995,9 @@
 	enum pipe pipe;
 	int level, plane;
 
+	if (!intel_has_sagv(dev_priv))
+		return false;
+
 	/*
 	 * SKL workaround: bspec recommends we disable the SAGV when we have
 	 * more then one pipe enabled