disp: msm: sde: serialize rm reserve for check only commit

During back to back mode set, current driver logic fails
atomic check during resource allocation with test only if
previous commit also with modeset, has tagged resources for
allocation but did not commit the resources yet. Since client
invoking atomic check before previous mode set commit complete
is an expected scenario now, instead of failing atomic check,
this change allows resource allocation for next commit also go
through by pollong till the first mode set is complete.

Change-Id: I1261b7d205bb0d886085664fab3664162a419c99
Signed-off-by: Prabhanjan Kandula <[email protected]>

msm/sde/sde_rm.c

@@ -34,6 +34,9 @@
 				(t).num_intf == (r).num_intf && \
 				(t).comp_type == (r).comp_type)
 
+/* ~one vsync poll time for rsvp_nxt to cleared by modeset from commit thread */
+#define RM_NXT_CLEAR_POLL_TIMEOUT_US 16600
+
 /**
  * toplogy information to be used when ctl path version does not
  * support driving more than one interface per ctl_path
@@ -2343,6 +2346,30 @@ static int _sde_rm_commit_rsvp(
 	return ret;
 }
 
+/* call this only after rm_mutex held */
+struct sde_rm_rsvp *_sde_rm_poll_get_rsvp_nxt_locked(struct sde_rm *rm,
+		struct drm_encoder *enc)
+{
+	int i;
+	u32 loop_count = 20;
+	struct sde_rm_rsvp *rsvp_nxt = NULL;
+	u32 sleep = RM_NXT_CLEAR_POLL_TIMEOUT_US / loop_count;
+
+	for (i = 0; i < loop_count; i++) {
+		rsvp_nxt = _sde_rm_get_rsvp_nxt(rm, enc);
+		if (!rsvp_nxt)
+			return rsvp_nxt;
+
+		mutex_unlock(&rm->rm_lock);
+		SDE_DEBUG("iteration i:%d sleep range:%uus to %uus\n",
+				i, sleep, sleep * 2);
+		usleep_range(sleep, sleep * 2);
+		mutex_lock(&rm->rm_lock);
+	}
+
+	return rsvp_nxt;
+}
+
 int sde_rm_reserve(
 		struct sde_rm *rm,
 		struct drm_encoder *enc,
@@ -2399,16 +2426,17 @@ int sde_rm_reserve(
 	 * commit rsvps. This rsvp_nxt can be cleared by a back to back
 	 * check_only commit with modeset when its predecessor atomic
 	 * commit is delayed / not committed the reservation yet.
-	 * Bail out in such cases so that check only commit
-	 * comes again after earlier commit gets processed.
+	 * Poll for rsvp_nxt clear, allow the check_only commit if rsvp_nxt
+	 * gets cleared and bailout if it does not get cleared before timeout.
 	 */
-
 	if (test_only && rsvp_cur && rsvp_nxt) {
-		SDE_ERROR("cur %d nxt %d enc %d conn %d\n", rsvp_cur->seq,
-			 rsvp_nxt->seq, enc->base.id,
-			 conn_state->connector->base.id);
-		ret = -EINVAL;
-		goto end;
+		rsvp_nxt = _sde_rm_poll_get_rsvp_nxt_locked(rm, enc);
+		if (rsvp_nxt) {
+			SDE_ERROR("poll timeout cur %d nxt %d enc %d\n",
+				rsvp_cur->seq, rsvp_nxt->seq, enc->base.id);
+			ret = -EINVAL;
+			goto end;
+		}
 	}
 
 	if (!test_only && rsvp_nxt)