drm/i915: Prepare to extract gen specific functions from intel_can_enable_sagv

Addressing one of the comments, recommending to extract platform
specific code from intel_can_enable_sagv as a preparation, before
we are going to add support for tgl+.

v2: - Removed whitespace
v3: - Removed premature debug and new cycle introduction(Ville)
    - Added missing no active pipes check(Ville)
v4: - Fixed stupid mistake with plane_state caused by stupid macro change
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200415145740.28241-1-stanislav.lisovskiy@intel.com

drivers/gpu/drm/i915/intel_pm.c

@@ -3757,42 +3757,22 @@ intel_disable_sagv(struct drm_i915_private *dev_priv)
 	return 0;
 }
 
-bool intel_can_enable_sagv(struct intel_atomic_state *state)
+static bool intel_crtc_can_enable_sagv(const struct intel_crtc_state *crtc_state)
 {
-	struct drm_device *dev = state->base.dev;
+	struct drm_device *dev = crtc_state->uapi.crtc->dev;
 	struct drm_i915_private *dev_priv = to_i915(dev);
-	struct intel_crtc *crtc;
+	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
 	struct intel_plane *plane;
-	struct intel_crtc_state *crtc_state;
-	enum pipe pipe;
 	int level, latency;
 
-	if (!intel_has_sagv(dev_priv))
-		return false;
-
-	/*
-	 * If there are no active CRTCs, no additional checks need be performed
-	 */
-	if (hweight8(state->active_pipes) == 0)
+	if (!crtc_state->hw.active)
 		return true;
 
-	/*
-	 * SKL+ workaround: bspec recommends we disable SAGV when we have
-	 * more then one pipe enabled
-	 */
-	if (hweight8(state->active_pipes) > 1)
-		return false;
-
-	/* Since we're now guaranteed to only have one active CRTC... */
-	pipe = ffs(state->active_pipes) - 1;
-	crtc = intel_get_crtc_for_pipe(dev_priv, pipe);
-	crtc_state = to_intel_crtc_state(crtc->base.state);
-
 	if (crtc_state->hw.adjusted_mode.flags & DRM_MODE_FLAG_INTERLACE)
 		return false;
 
 	for_each_intel_plane_on_crtc(dev, crtc, plane) {
-		struct skl_plane_wm *wm =
+		const struct skl_plane_wm *wm =
 			&crtc_state->wm.skl.optimal.planes[plane->id];
 
 		/* Skip this plane if it's not enabled */
@@ -3823,6 +3803,37 @@ bool intel_can_enable_sagv(struct intel_atomic_state *state)
 	return true;
 }
 
+bool intel_can_enable_sagv(struct intel_atomic_state *state)
+{
+	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
+	struct intel_crtc *crtc;
+	const struct intel_crtc_state *crtc_state;
+	enum pipe pipe;
+
+	if (!intel_has_sagv(dev_priv))
+		return false;
+
+	/*
+	 * If there are no active CRTCs, no additional checks need be performed
+	 */
+	if (hweight8(state->active_pipes) == 0)
+		return true;
+
+	/*
+	 * SKL+ workaround: bspec recommends we disable SAGV when we have
+	 * more then one pipe enabled
+	 */
+	if (hweight8(state->active_pipes) > 1)
+		return false;
+
+	/* Since we're now guaranteed to only have one active CRTC... */
+	pipe = ffs(state->active_pipes) - 1;
+	crtc = intel_get_crtc_for_pipe(dev_priv, pipe);
+	crtc_state = to_intel_crtc_state(crtc->base.state);
+
+	return intel_crtc_can_enable_sagv(crtc_state);
+}
+
 /*
  * Calculate initial DBuf slice offset, based on slice size
  * and mask(i.e if slice size is 1024 and second slice is enabled