[PATCH 05/14] drm/i915: Avoid triggering unwanted cdclk changes due to dbuf bandwidth changes

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Currently intel_bw_calc_min_cdclk() always adds the bw_state
to the atomic state. Not only does it result in potentially
redundant work later, it's also currently causing unwanted cdclk
changes during driver load.

Check if the dbuf bw is actually changing before we decide to
pull in the bw state.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_bw.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_bw.c b/drivers/gpu/drm/i915/display/intel_bw.c
index c9e15a068b67..16ae337376fe 100644
--- a/drivers/gpu/drm/i915/display/intel_bw.c
+++ b/drivers/gpu/drm/i915/display/intel_bw.c
@@ -1259,7 +1259,8 @@ int intel_bw_calc_min_cdclk(struct intel_atomic_state *state,
 	struct intel_bw_state *new_bw_state = NULL;
 	const struct intel_bw_state *old_bw_state = NULL;
 	const struct intel_cdclk_state *cdclk_state;
-	const struct intel_crtc_state *crtc_state;
+	const struct intel_crtc_state *old_crtc_state;
+	const struct intel_crtc_state *new_crtc_state;
 	int old_min_cdclk, new_min_cdclk;
 	struct intel_crtc *crtc;
 	int i;
@@ -1267,15 +1268,23 @@ int intel_bw_calc_min_cdclk(struct intel_atomic_state *state,
 	if (DISPLAY_VER(dev_priv) < 9)
 		return 0;
 
-	for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i) {
+	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state,
+					    new_crtc_state, i) {
+		struct intel_dbuf_bw old_dbuf_bw, new_dbuf_bw;
+
+		skl_crtc_calc_dbuf_bw(&old_dbuf_bw, old_crtc_state);
+		skl_crtc_calc_dbuf_bw(&new_dbuf_bw, new_crtc_state);
+
+		if (!intel_dbuf_bw_changed(dev_priv, &old_dbuf_bw, &new_dbuf_bw))
+			continue;
+
 		new_bw_state = intel_atomic_get_bw_state(state);
 		if (IS_ERR(new_bw_state))
 			return PTR_ERR(new_bw_state);
 
 		old_bw_state = intel_atomic_get_old_bw_state(state);
 
-		skl_crtc_calc_dbuf_bw(&new_bw_state->dbuf_bw[crtc->pipe],
-				      crtc_state);
+		new_bw_state->dbuf_bw[crtc->pipe] = new_dbuf_bw;
 	}
 
 	if (!old_bw_state)
-- 
2.45.3