drm/i915: Call kill_bigjoiner_slave() earlier

Let's do the kill_bigjoiner_slave() thing from
intel_bigjoiner_add_affected_crtcs() since it's related to
what we do there. This cleans up the logic in the
compute_config() loop a bit.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201124201156.17095-4-ville.syrjala@linux.intel.comReviewed-by: Manasi Navare <manasi.d.navare@intel.com>

drivers/gpu/drm/i915/display/intel_display.c

@@ -15335,21 +15335,16 @@ static int intel_atomic_check_bigjoiner(struct intel_atomic_state *state,
 	return -EINVAL;
 }
 
-static int kill_bigjoiner_slave(struct intel_atomic_state *state,
+static void kill_bigjoiner_slave(struct intel_atomic_state *state,
 				 struct intel_crtc_state *master_crtc_state)
 {
 	struct intel_crtc_state *slave_crtc_state =
-		intel_atomic_get_crtc_state(&state->base,
-					    master_crtc_state->bigjoiner_linked_crtc);
-
-	if (IS_ERR(slave_crtc_state))
-		return PTR_ERR(slave_crtc_state);
+		intel_atomic_get_new_crtc_state(state, master_crtc_state->bigjoiner_linked_crtc);
 
 	slave_crtc_state->bigjoiner = master_crtc_state->bigjoiner = false;
 	slave_crtc_state->bigjoiner_slave = master_crtc_state->bigjoiner_slave = false;
 	slave_crtc_state->bigjoiner_linked_crtc = master_crtc_state->bigjoiner_linked_crtc = NULL;
 	intel_crtc_copy_uapi_to_hw_state(state, slave_crtc_state);
-	return 0;
 }
 
 /**
@@ -15519,6 +15514,13 @@ static int intel_bigjoiner_add_affected_crtcs(struct intel_atomic_state *state)
 			return ret;
 	}
 
+	for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i) {
+		/* Kill old bigjoiner link, we may re-establish afterwards */
+		if (needs_modeset(crtc_state) &&
+		    crtc_state->bigjoiner && !crtc_state->bigjoiner_slave)
+			kill_bigjoiner_slave(state, crtc_state);
+	}
+
 	return 0;
 }
 
@@ -15560,13 +15562,6 @@ static int intel_atomic_check(struct drm_device *dev,
 			continue;
 		}
 
-		/* Kill old bigjoiner link, we may re-establish afterwards */
-		if (old_crtc_state->bigjoiner && !old_crtc_state->bigjoiner_slave) {
-			ret = kill_bigjoiner_slave(state, new_crtc_state);
-			if (ret)
-				goto fail;
-		}
-
 		if (!new_crtc_state->uapi.enable) {
 			if (!new_crtc_state->bigjoiner_slave) {
 				intel_crtc_copy_uapi_to_hw_state(state, new_crtc_state);