disp: msm: sde: avoid mis-allocating dummy mixers

Dummy mixers for dedicated concurrent writeback can be allocated
as valid mixers. However, they should only be allocated for DCWB
usecases. Allocating these virtual resources incorrectly can lead
to underrun on external monitors. These dummy mixers should not
be tracked as available resources and exposed to dp for
mode validation.

Change-Id: I04f583d5b722e0a384a5446e3a8a2313a338aa12
Signed-off-by: Nilaan Gunabalachandran <ngunabal@codeaurora.org>

msm/sde/sde_rm.c

@@ -190,9 +190,14 @@ static void _sde_rm_inc_resource_info_lm(struct sde_rm *rm,
 	struct sde_rm_hw_blk *blk2;
 	const struct sde_lm_cfg *lm_cfg, *lm_cfg2;
 
+	lm_cfg = to_sde_hw_mixer(blk->hw)->cap;
+
+	/* Do not track & expose dummy mixers */
+	if (lm_cfg->dummy_mixer)
+		return;
+
 	avail_res->num_lm++;
 
-	lm_cfg = to_sde_hw_mixer(blk->hw)->cap;
 	/* Check for 3d muxes by comparing paired lms */
 	list_for_each_entry(blk2, &rm->hw_blks[SDE_HW_BLK_LM], list) {
 		lm_cfg2 = to_sde_hw_mixer(blk2->hw)->cap;
@@ -215,9 +220,14 @@ static void _sde_rm_dec_resource_info_lm(struct sde_rm *rm,
 	struct sde_rm_hw_blk *blk2;
 	const struct sde_lm_cfg *lm_cfg, *lm_cfg2;
 
+	lm_cfg = to_sde_hw_mixer(blk->hw)->cap;
+
+	/* Do not track & expose dummy mixers */
+	if (lm_cfg->dummy_mixer)
+		return;
+
 	avail_res->num_lm--;
 
-	lm_cfg = to_sde_hw_mixer(blk->hw)->cap;
 	/* Check for 3d muxes by comparing paired lms */
 	list_for_each_entry(blk2, &rm->hw_blks[SDE_HW_BLK_LM], list) {
 		lm_cfg2 = to_sde_hw_mixer(blk2->hw)->cap;
@@ -1098,6 +1108,9 @@ static bool _sde_rm_check_lm_and_get_connected_blks(
 		    (RM_RQ_DCWB(reqs) && !dcwb_pref)) {
 			SDE_DEBUG("fail: cwb/dcwb supported lm not allocated\n");
 			return false;
+		} else if (!RM_RQ_DCWB(reqs) && dcwb_pref) {
+			SDE_DEBUG("fail: dcwb supported dummy lm incorrectly allocated\n");
+			return false;
 		}
 	} else if ((!is_conn_primary && lm_primary_pref) ||
 			(!is_conn_secondary && lm_secondary_pref)) {