drm/i915: Avoid triggering unwanted cdclk changes due to dbuf bandwidth changes

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@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250326162544.3642-6-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_bw.c b/drivers/gpu/drm/i915/display/intel_bw.c
index 67d088da1f3801b383ca9ed1990f4b34cef346dc..19b516084fac8bb3e8ecdd8a401844317c2bfcf0 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_bw.c
+++ b/drivers/gpu/drm/i915/display/intel_bw.c
@@ -1294,7 +1294,8 @@ 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;
@@ -1302,15 +1303,23 @@ int intel_bw_calc_min_cdclk(struct intel_atomic_state *state,
        if (DISPLAY_VER(display) < 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(display, &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)