linux-kernel - [PATCH 05/12] coresight-replicator: Handle delayed probe for CPU cluster replicator

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Message-Id: <20251027-cpu_cluster_component_pm-v1-5-31355ac588c2@oss.qualcomm.com>
Date: Mon, 27 Oct 2025 23:28:07 -0700
From: Yuanfang Zhang <yuanfang.zhang@....qualcomm.com>
To: Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        James Clark <james.clark@...aro.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Leo Yan <leo.yan@...ux.dev>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Cc: kernel@....qualcomm.com, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Yuanfang Zhang <yuanfang.zhang@....qualcomm.com>
Subject: [PATCH 05/12] coresight-replicator: Handle delayed probe for CPU
 cluster replicator

Delay probe the CPU cluster replicator when all CPUs of the cluster are
offline, and re-probe the replicator when any CPU in the cluster comes
online.

Key changes:
- Maintain a global list to track delayed replicators waiting for
  CPU online.
- Add a CPU hotplug callback to retry registration on CPU online events.

Signed-off-by: Yuanfang Zhang <yuanfang.zhang@....qualcomm.com>
---
 drivers/hwtracing/coresight/coresight-replicator.c | 65 ++++++++++++++++++++--
 1 file changed, 61 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-replicator.c b/drivers/hwtracing/coresight/coresight-replicator.c
index c5a9c7a2adfa90ae22890ed730fc008fe6901778..1dfe11940cd6001db3cf17249b0493027b65e19c 100644
--- a/drivers/hwtracing/coresight/coresight-replicator.c
+++ b/drivers/hwtracing/coresight/coresight-replicator.c
@@ -26,6 +26,9 @@
 #define REPLICATOR_IDFILTER1		0x004
 
 DEFINE_CORESIGHT_DEVLIST(replicator_devs, "replicator");
+static LIST_HEAD(replicator_delay_probe);
+static enum cpuhp_state hp_online;
+static DEFINE_SPINLOCK(delay_lock);
 
 /**
  * struct replicator_drvdata - specifics associated to a replicator component
@@ -37,6 +40,8 @@ DEFINE_CORESIGHT_DEVLIST(replicator_devs, "replicator");
  * @spinlock:	serialize enable/disable operations.
  * @check_idfilter_val: check if the context is lost upon clock removal.
  * @cpumask:	CPU mask representing the CPUs related to this replicator.
+ * @dev:	pointer to the device associated with this replicator.
+ * @link:	link to the delay_probed list.
  */
 struct replicator_drvdata {
 	void __iomem		*base;
@@ -46,6 +51,8 @@ struct replicator_drvdata {
 	raw_spinlock_t		spinlock;
 	bool			check_idfilter_val;
 	struct cpumask		*cpumask;
+	struct device		*dev;
+	struct list_head	link;
 };
 
 struct replicator_smp_arg {
@@ -395,7 +402,7 @@ static int replicator_probe(struct device *dev, struct resource *res)
 		drvdata->cpumask = replicator_get_cpumask(dev);
 		if (!drvdata->cpumask)
 			return -EINVAL;
-
+		drvdata->dev = dev;
 		cpus_read_lock();
 		for_each_cpu(cpu, drvdata->cpumask) {
 			ret = smp_call_function_single(cpu,
@@ -403,10 +410,15 @@ static int replicator_probe(struct device *dev, struct resource *res)
 			if (!ret)
 				break;
 		}
-		cpus_read_unlock();
 
-		if (ret)
+		if (ret) {
+			scoped_guard(spinlock,  &delay_lock)
+				list_add(&drvdata->link, &replicator_delay_probe);
+			cpus_read_unlock();
 			return 0;
+		}
+
+		cpus_read_unlock();
 	} else if (res) {
 		replicator_init_hw(drvdata);
 	}
@@ -420,8 +432,13 @@ static int replicator_remove(struct device *dev)
 {
 	struct replicator_drvdata *drvdata = dev_get_drvdata(dev);
 
-	if (drvdata->csdev)
+	if (drvdata->csdev) {
 		coresight_unregister(drvdata->csdev);
+	} else {
+		scoped_guard(spinlock,  &delay_lock)
+			list_del(&drvdata->link);
+	}
+
 	return 0;
 }
 
@@ -554,8 +571,44 @@ static struct amba_driver dynamic_replicator_driver = {
 	.id_table	= dynamic_replicator_ids,
 };
 
+static int replicator_online_cpu(unsigned int cpu)
+{
+	struct replicator_drvdata *drvdata, *tmp;
+	int ret;
+
+	spin_lock(&delay_lock);
+	list_for_each_entry_safe(drvdata, tmp, &replicator_delay_probe, link) {
+		if (cpumask_test_cpu(cpu, drvdata->cpumask)) {
+			list_del(&drvdata->link);
+			spin_unlock(&delay_lock);
+			ret = pm_runtime_resume_and_get(drvdata->dev);
+			if (ret < 0)
+				return 0;
+
+			replicator_clear_self_claim_tag(drvdata);
+			replicator_reset(drvdata);
+			replicator_add_coresight_dev(drvdata->dev);
+			pm_runtime_put(drvdata->dev);
+			spin_lock(&delay_lock);
+		}
+	}
+	spin_unlock(&delay_lock);
+	return 0;
+}
+
 static int __init replicator_init(void)
 {
+	int ret;
+
+	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+					"arm/coresight-replicator:online",
+					replicator_online_cpu, NULL);
+
+	if (ret > 0)
+		hp_online = ret;
+	else
+		return ret;
+
 	return coresight_init_driver("replicator", &dynamic_replicator_driver, &replicator_driver,
 				     THIS_MODULE);
 }
@@ -563,6 +616,10 @@ static int __init replicator_init(void)
 static void __exit replicator_exit(void)
 {
 	coresight_remove_driver(&dynamic_replicator_driver, &replicator_driver);
+	if (hp_online) {
+		cpuhp_remove_state_nocalls(hp_online);
+		hp_online = 0;
+	}
 }
 
 module_init(replicator_init);

-- 
2.34.1