interconnect: qcom: Support bcm-voter-specific TCS wait behavior

Currently, all bcm-voters set tcs_cmd::wait=true for the last VCD
command in each TCS (AMC, WAKE, and SLEEP). However, some bcm-voters
don't need the completion and instead need to optimize for latency. For
instance, disabling wait-for-completion in the WAKE set can decrease
resume latency and allow for certain operations to occur in parallel
with the WAKE TCS triggering. This is only safe in very specific
situations. Keep the default behavior of always waiting, but allow it to
be overridden in devicetree.

Signed-off-by: Mike Tipton <mdtipton@codeaurora.org>
Link: https://lore.kernel.org/r/20200903192149.30385-5-mdtipton@codeaurora.org
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>

Author: Mike Tipton

drivers/interconnect/qcom/bcm-voter.c

@@ -27,6 +27,7 @@ static DEFINE_MUTEX(bcm_voter_lock);
  * @commit_list: list containing bcms to be committed to hardware
  * @ws_list: list containing bcms that have different wake/sleep votes
  * @voter_node: list of bcm voters
+ * @tcs_wait: mask for which buckets require TCS completion
  */
 struct bcm_voter {
 	struct device *dev;
@@ -35,6 +36,7 @@ struct bcm_voter {
 	struct list_head commit_list;
 	struct list_head ws_list;
 	struct list_head voter_node;
+	u32 tcs_wait;
 };
 
 static int cmp_vcd(void *priv, struct list_head *a, struct list_head *b)
@@ -100,7 +102,7 @@ static void bcm_aggregate(struct qcom_icc_bcm *bcm)
 }
 
 static inline void tcs_cmd_gen(struct tcs_cmd *cmd, u64 vote_x, u64 vote_y,
-			       u32 addr, bool commit)
+			       u32 addr, bool commit, bool wait)
 {
 	bool valid = true;
 
@@ -125,15 +127,16 @@ static inline void tcs_cmd_gen(struct tcs_cmd *cmd, u64 vote_x, u64 vote_y,
 	 * Set the wait for completion flag on command that need to be completed
 	 * before the next command.
 	 */
-	cmd->wait = commit;
+	cmd->wait = wait;
 }
 
-static void tcs_list_gen(struct list_head *bcm_list, int bucket,
-			 struct tcs_cmd tcs_list[MAX_BCMS],
+static void tcs_list_gen(struct bcm_voter *voter, int bucket,
+			 struct tcs_cmd tcs_list[MAX_VCD],
 			 int n[MAX_VCD + 1])
 {
+	struct list_head *bcm_list = &voter->commit_list;
 	struct qcom_icc_bcm *bcm;
-	bool commit;
+	bool commit, wait;
 	size_t idx = 0, batch = 0, cur_vcd_size = 0;
 
 	memset(n, 0, sizeof(int) * (MAX_VCD + 1));
@@ -146,8 +149,11 @@ static void tcs_list_gen(struct list_head *bcm_list, int bucket,
 			commit = true;
 			cur_vcd_size = 0;
 		}
+
+		wait = commit && (voter->tcs_wait & BIT(bucket));
+
 		tcs_cmd_gen(&tcs_list[idx], bcm->vote_x[bucket],
-			    bcm->vote_y[bucket], bcm->addr, commit);
+			    bcm->vote_y[bucket], bcm->addr, commit, wait);
 		idx++;
 		n[batch]++;
 		/*
@@ -272,8 +278,7 @@ int qcom_icc_bcm_voter_commit(struct bcm_voter *voter)
 	 * Construct the command list based on a pre ordered list of BCMs
 	 * based on VCD.
 	 */
-	tcs_list_gen(&voter->commit_list, QCOM_ICC_BUCKET_AMC, cmds, commit_idx);
-
+	tcs_list_gen(voter, QCOM_ICC_BUCKET_AMC, cmds, commit_idx);
 	if (!commit_idx[0])
 		goto out;
 
@@ -309,15 +314,15 @@ int qcom_icc_bcm_voter_commit(struct bcm_voter *voter)
 
 	list_sort(NULL, &voter->commit_list, cmp_vcd);
 
-	tcs_list_gen(&voter->commit_list, QCOM_ICC_BUCKET_WAKE, cmds, commit_idx);
+	tcs_list_gen(voter, QCOM_ICC_BUCKET_WAKE, cmds, commit_idx);
 
 	ret = rpmh_write_batch(voter->dev, RPMH_WAKE_ONLY_STATE, cmds, commit_idx);
 	if (ret) {
 		pr_err("Error sending WAKE RPMH requests (%d)\n", ret);
 		goto out;
 	}
 
-	tcs_list_gen(&voter->commit_list, QCOM_ICC_BUCKET_SLEEP, cmds, commit_idx);
+	tcs_list_gen(voter, QCOM_ICC_BUCKET_SLEEP, cmds, commit_idx);
 
 	ret = rpmh_write_batch(voter->dev, RPMH_SLEEP_STATE, cmds, commit_idx);
 	if (ret) {
@@ -336,14 +341,19 @@ EXPORT_SYMBOL_GPL(qcom_icc_bcm_voter_commit);
 
 static int qcom_icc_bcm_voter_probe(struct platform_device *pdev)
 {
+	struct device_node *np = pdev->dev.of_node;
 	struct bcm_voter *voter;
 
 	voter = devm_kzalloc(&pdev->dev, sizeof(*voter), GFP_KERNEL);
 	if (!voter)
 		return -ENOMEM;
 
 	voter->dev = &pdev->dev;
-	voter->np = pdev->dev.of_node;
+	voter->np = np;
+
+	if (of_property_read_u32(np, "qcom,tcs-wait", &voter->tcs_wait))
+		voter->tcs_wait = QCOM_ICC_TAG_ALWAYS;
+
 	mutex_init(&voter->lock);
 	INIT_LIST_HEAD(&voter->commit_list);
 	INIT_LIST_HEAD(&voter->ws_list);