drm/msm/dpu: simplify peer LM handling

For each LM there is at max 1 peer LM. Thus there is no need to have a
mask for the peer LM enumeration. Change that to have an ID of the peer LM.
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Tested-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/545352/
Link: https://lore.kernel.org/r/20230704022136.130522-4-dmitry.baryshkov@linaro.org

drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c

@@ -394,7 +394,7 @@ static const struct dpu_sspp_sub_blks qcm2290_dma_sblk_0 = _DMA_SBLK("8", 1);
 	.features = _fmask, \
 	.sblk = _sblk, \
 	.pingpong = _pp, \
-	.lm_pair_mask = (1 << _lmpair), \
+	.lm_pair = _lmpair, \
 	.dspp = _dspp \
 	}
 

drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h

@@ -554,14 +554,14 @@ struct dpu_sspp_cfg {
  * @features           bit mask identifying sub-blocks/features
  * @sblk:              LM Sub-blocks information
  * @pingpong:          ID of connected PingPong, PINGPONG_NONE if unsupported
- * @lm_pair_mask:      Bitmask of LMs that can be controlled by same CTL
+ * @lm_pair:           ID of LM that can be controlled by same CTL
  */
 struct dpu_lm_cfg {
 	DPU_HW_BLK_INFO;
 	const struct dpu_lm_sub_blks *sblk;
 	u32 pingpong;
 	u32 dspp;
-	unsigned long lm_pair_mask;
+	unsigned long lm_pair;
 };
 
 /**

drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c

@@ -253,28 +253,19 @@ static bool _dpu_rm_needs_split_display(const struct msm_display_topology *top)
 }
 
 /**
- * _dpu_rm_check_lm_peer - check if a mixer is a peer of the primary
+ * _dpu_rm_get_lm_peer - get the id of a mixer which is a peer of the primary
  * @rm: dpu resource manager handle
  * @primary_idx: index of primary mixer in rm->mixer_blks[]
- * @peer_idx: index of other mixer in rm->mixer_blks[]
- * Return: true if rm->mixer_blks[peer_idx] is a peer of
- *          rm->mixer_blks[primary_idx]
  */
-static bool _dpu_rm_check_lm_peer(struct dpu_rm *rm, int primary_idx,
-		int peer_idx)
+static int _dpu_rm_get_lm_peer(struct dpu_rm *rm, int primary_idx)
 {
 	const struct dpu_lm_cfg *prim_lm_cfg;
-	const struct dpu_lm_cfg *peer_cfg;
 
 	prim_lm_cfg = to_dpu_hw_mixer(rm->mixer_blks[primary_idx])->cap;
-	peer_cfg = to_dpu_hw_mixer(rm->mixer_blks[peer_idx])->cap;
 
-	if (!test_bit(peer_cfg->id, &prim_lm_cfg->lm_pair_mask)) {
-		DPU_DEBUG("lm %d not peer of lm %d\n", peer_cfg->id,
-				peer_cfg->id);
-		return false;
-	}
-	return true;
+	if (prim_lm_cfg->lm_pair >= LM_0 && prim_lm_cfg->lm_pair < LM_MAX)
+		return prim_lm_cfg->lm_pair - LM_0;
+	return -EINVAL;
 }
 
 /**
@@ -351,7 +342,7 @@ static int _dpu_rm_reserve_lms(struct dpu_rm *rm,
 	int lm_idx[MAX_BLOCKS];
 	int pp_idx[MAX_BLOCKS];
 	int dspp_idx[MAX_BLOCKS] = {0};
-	int i, j, lm_count = 0;
+	int i, lm_count = 0;
 
 	if (!reqs->topology.num_lm) {
 		DPU_ERROR("invalid number of lm: %d\n", reqs->topology.num_lm);
@@ -376,16 +367,15 @@ static int _dpu_rm_reserve_lms(struct dpu_rm *rm,
 		++lm_count;
 
 		/* Valid primary mixer found, find matching peers */
-		for (j = i + 1; j < ARRAY_SIZE(rm->mixer_blks) &&
-				lm_count < reqs->topology.num_lm; j++) {
-			if (!rm->mixer_blks[j])
+		if (lm_count < reqs->topology.num_lm) {
+			int j = _dpu_rm_get_lm_peer(rm, i);
+
+			/* ignore the peer if there is an error or if the peer was already processed */
+			if (j < 0 || j < i)
 				continue;
 
-			if (!_dpu_rm_check_lm_peer(rm, i, j)) {
-				DPU_DEBUG("lm %d not peer of lm %d\n", LM_0 + j,
-						LM_0 + i);
+			if (!rm->mixer_blks[j])
 				continue;
-			}
 
 			if (!_dpu_rm_check_lm_and_get_connected_blks(rm,
 					global_state, enc_id, j,