drm/i915: Extract skl SAGV checking

Introduce platform dependent SAGV checking in
combination with bandwidth state pipe SAGV mask.

This is preparation to adding TGL support, which
requires different way of SAGV checking.

v2, v3, v4, v5, v6: Fix rebase conflict

v7: - Nuke icl specific function, use skl
      for icl as well, gen specific active_pipes
      check to be added in the next patch(Ville)

v8: - Use more generic intel_crtc_can_enable_sagv
      for checking(Ville)
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/20200513093816.11466-3-stanislav.lisovskiy@intel.com

drivers/gpu/drm/i915/intel_pm.c

@@ -3804,7 +3804,7 @@ void intel_sagv_post_plane_update(struct intel_atomic_state *state)
 		intel_enable_sagv(dev_priv);
 }
 
-static bool intel_crtc_can_enable_sagv(const struct intel_crtc_state *crtc_state)
+static bool skl_crtc_can_enable_sagv(const struct intel_crtc_state *crtc_state)
 {
 	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
@@ -3853,6 +3853,11 @@ static bool intel_crtc_can_enable_sagv(const struct intel_crtc_state *crtc_state
 	return true;
 }
 
+static bool intel_crtc_can_enable_sagv(const struct intel_crtc_state *crtc_state)
+{
+	return skl_crtc_can_enable_sagv(crtc_state);
+}
+
 bool intel_can_enable_sagv(const struct intel_bw_state *bw_state)
 {
 	if (bw_state->active_pipes && !is_power_of_2(bw_state->active_pipes))
@@ -3865,7 +3870,7 @@ static int intel_compute_sagv_mask(struct intel_atomic_state *state)
 {
 	int ret;
 	struct intel_crtc *crtc;
-	struct intel_crtc_state *new_crtc_state;
+	const struct intel_crtc_state *new_crtc_state;
 	struct intel_bw_state *new_bw_state = NULL;
 	const struct intel_bw_state *old_bw_state = NULL;
 	int i;
@@ -3889,6 +3894,7 @@ static int intel_compute_sagv_mask(struct intel_atomic_state *state)
 
 	new_bw_state->active_pipes =
 		intel_calc_active_pipes(state, old_bw_state->active_pipes);
+
 	if (new_bw_state->active_pipes != old_bw_state->active_pipes) {
 		ret = intel_atomic_lock_global_state(&new_bw_state->base);
 		if (ret)