drm/i915: Add pre/post plane updates for SAGV

Lets have a unified way to handle SAGV changes,
espoecially considering the upcoming Gen12 changes.

Current "standard" way of doing this in commit_tail
is pre/post plane updates, when everything which
has to be forbidden and not supported in new config
has to be restricted before update and relaxed after
plane update.

v2: - Removed unneeded returns(Ville)

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
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/20200415143911.10244-5-stanislav.lisovskiy@intel.com
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 1e7f9be..d54833a 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3757,6 +3757,22 @@ intel_disable_sagv(struct drm_i915_private *dev_priv)
 	return 0;
 }
 
+void intel_sagv_pre_plane_update(struct intel_atomic_state *state)
+{
+	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
+
+	if (!intel_can_enable_sagv(state))
+		intel_disable_sagv(dev_priv);
+}
+
+void intel_sagv_post_plane_update(struct intel_atomic_state *state)
+{
+	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
+
+	if (intel_can_enable_sagv(state))
+		intel_enable_sagv(dev_priv);
+}
+
 static bool intel_crtc_can_enable_sagv(const struct intel_crtc_state *crtc_state)
 {
 	struct drm_device *dev = crtc_state->uapi.crtc->dev;