drm/msm/mdp5: Stage border out on base stage if CRTC has 2 LMs

If a CRTC comprises of 2 LMs, it is mandatory to enable border out
and assign it to the base stage.

We had to enable border out also when the base plane wasn't fullscreen.
Club these checks and put them in a separate function called
get_start_stage() that returns the starting stage for assigning planes.
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c

@@ -512,6 +512,29 @@ static bool is_fullscreen(struct drm_crtc_state *cstate,
 		((pstate->crtc_y + pstate->crtc_h) >= cstate->mode.vdisplay);
 }
 
+enum mdp_mixer_stage_id get_start_stage(struct drm_crtc *crtc,
+					struct drm_crtc_state *new_crtc_state,
+					struct drm_plane_state *bpstate)
+{
+	struct mdp5_crtc_state *mdp5_cstate =
+			to_mdp5_crtc_state(new_crtc_state);
+
+	/*
+	 * if we're in source split mode, it's mandatory to have
+	 * border out on the base stage
+	 */
+	if (mdp5_cstate->pipeline.r_mixer)
+		return STAGE0;
+
+	/* if the bottom-most layer is not fullscreen, we need to use
+	 * it for solid-color:
+	 */
+	if (!is_fullscreen(new_crtc_state, bpstate))
+		return STAGE0;
+
+	return STAGE_BASE;
+}
+
 static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
 		struct drm_crtc_state *state)
 {
@@ -522,8 +545,9 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
 	const struct mdp5_cfg_hw *hw_cfg;
 	const struct drm_plane_state *pstate;
 	bool cursor_plane = false;
-	int cnt = 0, base = 0, i;
+	int cnt = 0, i;
 	int ret;
+	enum mdp_mixer_stage_id start;
 
 	DBG("%s: check", crtc->name);
 
@@ -537,6 +561,10 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
 			cursor_plane = true;
 	}
 
+	/* bail out early if there aren't any planes */
+	if (!cnt)
+		return 0;
+
 	ret = mdp5_crtc_setup_pipeline(crtc, state);
 	if (ret) {
 		dev_err(dev->dev, "couldn't assign mixers %d\n", ret);
@@ -546,23 +574,20 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
 	/* assign a stage based on sorted zpos property */
 	sort(pstates, cnt, sizeof(pstates[0]), pstate_cmp, NULL);
 
-	/* if the bottom-most layer is not fullscreen, we need to use
-	 * it for solid-color:
-	 */
-	if ((cnt > 0) && !is_fullscreen(state, &pstates[0].state->base))
-		base++;
-
 	/* trigger a warning if cursor isn't the highest zorder */
 	WARN_ON(cursor_plane &&
 		(pstates[cnt - 1].plane->type != DRM_PLANE_TYPE_CURSOR));
 
+	start = get_start_stage(crtc, state, &pstates[0].state->base);
+
 	/* verify that there are not too many planes attached to crtc
 	 * and that we don't have conflicting mixer stages:
 	 */
 	hw_cfg = mdp5_cfg_get_hw_config(mdp5_kms->cfg);
 
-	if ((cnt + base) >= hw_cfg->lm.nb_stages) {
-		dev_err(dev->dev, "too many planes! cnt=%d, base=%d\n", cnt, base);
+	if ((cnt + start - 1) >= hw_cfg->lm.nb_stages) {
+		dev_err(dev->dev, "too many planes! cnt=%d, start stage=%d\n",
+			cnt, start);
 		return -EINVAL;
 	}
 
@@ -570,7 +595,7 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
 		if (cursor_plane && (i == (cnt - 1)))
 			pstates[i].state->stage = hw_cfg->lm.nb_stages;
 		else
-			pstates[i].state->stage = STAGE_BASE + i + base;
+			pstates[i].state->stage = start + i;
 		DBG("%s: assign pipe %s on stage=%d", crtc->name,
 				pstates[i].plane->name,
 				pstates[i].state->stage);