drm/msm/mdp5: Assign 'right' mixer to CRTC state

Dynamically assign a right mixer to mdp5_crtc_state in the CRTC's
atomic_check path. Assigning the right mixer has some constraints,
i.e, only a few LMs can be paired together. Update mdp5_mixer_assign
to handle these constraints.

Firstly, we need to identify whether we need a right mixer or not.
At the moment, there are 2 scenarios where a right mixer might be
needed:
- If any of the planes connected to this CRTC is too wide (i.e, is
  comprised of 2 hwpipes).
- If the CRTC's mode itself is too wide (i.e, a 4K mode on HDMI).

We implement both these checks in the mdp5_crtc_atomic_check(), and
pass 'need_right_mixer' to mdp5_setup_pipeline.

If a CRTC is already assigned a single mixer, and a new atomic commit
brings in a drm_plane that needs 2 hwpipes, we can successfully commit
this mode without requiring a full modeset, provided that we still use
the previously assigned mixer as the left mixer. If such an assignment
isn't possible, we'd need to do a full modeset. This scenario has been
ignored for now.

The mixer assignment code is a bit messy, considering we have at most
4 LM instances in hardware. This can probably be re-visited later with
simplified logic.
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

@@ -449,7 +449,8 @@ static void mdp5_crtc_enable(struct drm_crtc *crtc)
 }
 
 int mdp5_crtc_setup_pipeline(struct drm_crtc *crtc,
-			     struct drm_crtc_state *new_crtc_state)
+			     struct drm_crtc_state *new_crtc_state,
+			     bool need_right_mixer)
 {
 	struct mdp5_crtc_state *mdp5_cstate =
 			to_mdp5_crtc_state(new_crtc_state);
@@ -459,15 +460,32 @@ int mdp5_crtc_setup_pipeline(struct drm_crtc *crtc,
 
 	new_mixer = !pipeline->mixer;
 
+	if ((need_right_mixer && !pipeline->r_mixer) ||
+	    (!need_right_mixer && pipeline->r_mixer))
+		new_mixer = true;
+
 	if (new_mixer) {
 		struct mdp5_hw_mixer *old_mixer = pipeline->mixer;
+		struct mdp5_hw_mixer *old_r_mixer = pipeline->r_mixer;
+		u32 caps;
+		int ret;
+
+		caps = MDP_LM_CAP_DISPLAY;
+		if (need_right_mixer)
+			caps |= MDP_LM_CAP_PAIR;
 
-		pipeline->mixer = mdp5_mixer_assign(new_crtc_state->state, crtc,
-						    MDP_LM_CAP_DISPLAY);
-		if (IS_ERR(pipeline->mixer))
-			return PTR_ERR(pipeline->mixer);
+		ret = mdp5_mixer_assign(new_crtc_state->state, crtc, caps,
+					&pipeline->mixer, need_right_mixer ?
+					&pipeline->r_mixer : NULL);
+		if (ret)
+			return ret;
 
 		mdp5_mixer_release(new_crtc_state->state, old_mixer);
+		if (old_r_mixer) {
+			mdp5_mixer_release(new_crtc_state->state, old_r_mixer);
+			if (!need_right_mixer)
+				pipeline->r_mixer = NULL;
+		}
 	}
 
 	/*
@@ -544,7 +562,9 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
 	struct plane_state pstates[STAGE_MAX + 1];
 	const struct mdp5_cfg_hw *hw_cfg;
 	const struct drm_plane_state *pstate;
+	const struct drm_display_mode *mode = &state->adjusted_mode;
 	bool cursor_plane = false;
+	bool need_right_mixer = false;
 	int cnt = 0, i;
 	int ret;
 	enum mdp_mixer_stage_id start;
@@ -555,6 +575,12 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
 		pstates[cnt].plane = plane;
 		pstates[cnt].state = to_mdp5_plane_state(pstate);
 
+		/*
+		 * if any plane on this crtc uses 2 hwpipes, then we need
+		 * the crtc to have a right hwmixer.
+		 */
+		if (pstates[cnt].state->r_hwpipe)
+			need_right_mixer = true;
 		cnt++;
 
 		if (plane->type == DRM_PLANE_TYPE_CURSOR)
@@ -565,7 +591,16 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
 	if (!cnt)
 		return 0;
 
-	ret = mdp5_crtc_setup_pipeline(crtc, state);
+	hw_cfg = mdp5_cfg_get_hw_config(mdp5_kms->cfg);
+
+	/*
+	 * we need a right hwmixer if the mode's width is greater than a single
+	 * LM's max width
+	 */
+	if (mode->hdisplay > hw_cfg->lm.max_width)
+		need_right_mixer = true;
+
+	ret = mdp5_crtc_setup_pipeline(crtc, state, need_right_mixer);
 	if (ret) {
 		dev_err(dev->dev, "couldn't assign mixers %d\n", ret);
 		return ret;
@@ -583,8 +618,6 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
 	/* 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 + start - 1) >= hw_cfg->lm.nb_stages) {
 		dev_err(dev->dev, "too many planes! cnt=%d, start stage=%d\n",
 			cnt, start);

drivers/gpu/drm/msm/mdp/mdp5/mdp5_mixer.c

@@ -16,42 +16,115 @@
 
 #include "mdp5_kms.h"
 
-struct mdp5_hw_mixer *mdp5_mixer_assign(struct drm_atomic_state *s,
-					struct drm_crtc *crtc, uint32_t caps)
+/*
+ * As of now, there are only 2 combinations possible for source split:
+ *
+ * Left | Right
+ * -----|------
+ *  LM0 | LM1
+ *  LM2 | LM5
+ *
+ */
+static int lm_right_pair[] = { 1, -1, 5, -1, -1, -1 };
+
+static int get_right_pair_idx(struct mdp5_kms *mdp5_kms, int lm)
+{
+	int i;
+	int pair_lm;
+
+	pair_lm = lm_right_pair[lm];
+	if (pair_lm < 0)
+		return -EINVAL;
+
+	for (i = 0; i < mdp5_kms->num_hwmixers; i++) {
+		struct mdp5_hw_mixer *mixer = mdp5_kms->hwmixers[i];
+
+		if (mixer->lm == pair_lm)
+			return mixer->idx;
+	}
+
+	return -1;
+}
+
+int mdp5_mixer_assign(struct drm_atomic_state *s, struct drm_crtc *crtc,
+		      uint32_t caps, struct mdp5_hw_mixer **mixer,
+		      struct mdp5_hw_mixer **r_mixer)
 {
 	struct msm_drm_private *priv = s->dev->dev_private;
 	struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(priv->kms));
 	struct mdp5_state *state = mdp5_get_state(s);
 	struct mdp5_hw_mixer_state *new_state;
-	struct mdp5_hw_mixer *mixer = NULL;
 	int i;
 
 	if (IS_ERR(state))
-		return ERR_CAST(state);
+		return PTR_ERR(state);
 
 	new_state = &state->hwmixer;
 
 	for (i = 0; i < mdp5_kms->num_hwmixers; i++) {
 		struct mdp5_hw_mixer *cur = mdp5_kms->hwmixers[i];
 
-		/* skip if already in-use */
-		if (new_state->hwmixer_to_crtc[cur->idx])
+		/*
+		 * skip if already in-use by a different CRTC. If there is a
+		 * mixer already assigned to this CRTC, it means this call is
+		 * a request to get an additional right mixer. Assume that the
+		 * existing mixer is the 'left' one, and try to see if we can
+		 * get its corresponding 'right' pair.
+		 */
+		if (new_state->hwmixer_to_crtc[cur->idx] &&
+		    new_state->hwmixer_to_crtc[cur->idx] != crtc)
 			continue;
 
 		/* skip if doesn't support some required caps: */
 		if (caps & ~cur->caps)
 			continue;
 
-		if (!mixer)
-			mixer = cur;
+		if (r_mixer) {
+			int pair_idx;
+
+			pair_idx = get_right_pair_idx(mdp5_kms, cur->lm);
+			if (pair_idx < 0)
+				return -EINVAL;
+
+			if (new_state->hwmixer_to_crtc[pair_idx])
+				continue;
+
+			*r_mixer = mdp5_kms->hwmixers[pair_idx];
 		}
 
-	if (!mixer)
-		return ERR_PTR(-ENOMEM);
+		/*
+		 * prefer a pair-able LM over an unpairable one. We can
+		 * switch the CRTC from Normal mode to Source Split mode
+		 * without requiring a full modeset if we had already
+		 * assigned this CRTC a pair-able LM.
+		 *
+		 * TODO: There will be assignment sequences which would
+		 * result in the CRTC requiring a full modeset, even
+		 * if we have the LM resources to prevent it. For a platform
+		 * with a few displays, we don't run out of pair-able LMs
+		 * so easily. For now, ignore the possibility of requiring
+		 * a full modeset.
+		 */
+		if (!(*mixer) || cur->caps & MDP_LM_CAP_PAIR)
+			*mixer = cur;
+	}
 
-	new_state->hwmixer_to_crtc[mixer->idx] = crtc;
+	if (!(*mixer))
+		return -ENOMEM;
 
-	return mixer;
+	if (r_mixer && !(*r_mixer))
+		return -ENOMEM;
+
+	DBG("assigning Layer Mixer %d to crtc %s", (*mixer)->lm, crtc->name);
+
+	new_state->hwmixer_to_crtc[(*mixer)->idx] = crtc;
+	if (r_mixer) {
+		DBG("assigning Right Layer Mixer %d to crtc %s", (*r_mixer)->lm,
+		    crtc->name);
+		new_state->hwmixer_to_crtc[(*r_mixer)->idx] = crtc;
+	}
+
+	return 0;
 }
 
 void mdp5_mixer_release(struct drm_atomic_state *s, struct mdp5_hw_mixer *mixer)

drivers/gpu/drm/msm/mdp/mdp5/mdp5_mixer.h

@@ -38,8 +38,9 @@ struct mdp5_hw_mixer_state {
 
 struct mdp5_hw_mixer *mdp5_mixer_init(const struct mdp5_lm_instance *lm);
 void mdp5_mixer_destroy(struct mdp5_hw_mixer *lm);
-struct mdp5_hw_mixer *mdp5_mixer_assign(struct drm_atomic_state *s,
-					struct drm_crtc *crtc, uint32_t caps);
+int mdp5_mixer_assign(struct drm_atomic_state *s, struct drm_crtc *crtc,
+		      uint32_t caps, struct mdp5_hw_mixer **mixer,
+		      struct mdp5_hw_mixer **r_mixer);
 void mdp5_mixer_release(struct drm_atomic_state *s,
 			struct mdp5_hw_mixer *mixer);