linux-kernel - [PATCH 03/12] coresight-funnel: Handle delay probe for CPU cluster funnel

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Message-Id: <20251027-cpu_cluster_component_pm-v1-3-31355ac588c2@oss.qualcomm.com>
Date: Mon, 27 Oct 2025 23:28:05 -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 03/12] coresight-funnel: Handle delay probe for CPU cluster
 funnel

Delay probe the cpu cluster funnel when all CPUs of this cluster are
offline, re-probe the funnel when any CPU in the cluster comes online.

Key changes:
- Introduce a global list to track delayed funnels waiting for CPU online.
- Add CPU hotplug callback to retry registration when the CPU comes up.

Signed-off-by: Yuanfang Zhang <yuanfang.zhang@....qualcomm.com>
---
 drivers/hwtracing/coresight/coresight-funnel.c | 62 +++++++++++++++++++++++---
 1 file changed, 57 insertions(+), 5 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-funnel.c b/drivers/hwtracing/coresight/coresight-funnel.c
index 12c29eb98b2122a3ade4cbed9a0d91c67ec777ed..43b9287a865eb26ce021521e4a5f193c48188bba 100644
--- a/drivers/hwtracing/coresight/coresight-funnel.c
+++ b/drivers/hwtracing/coresight/coresight-funnel.c
@@ -32,6 +32,9 @@
 #define FUNNEL_ENSx_MASK	0xff
 
 DEFINE_CORESIGHT_DEVLIST(funnel_devs, "funnel");
+static LIST_HEAD(funnel_delay_probe);
+static enum cpuhp_state hp_online;
+static DEFINE_SPINLOCK(delay_lock);
 
 /**
  * struct funnel_drvdata - specifics associated to a funnel component
@@ -42,6 +45,8 @@ DEFINE_CORESIGHT_DEVLIST(funnel_devs, "funnel");
  * @priority:	port selection order.
  * @spinlock:	serialize enable/disable operations.
  * @cpumask:	CPU mask representing the CPUs related to this funnel.
+ * @dev:	pointer to the device associated with this funnel.
+ * @link:	list node for adding this funnel to the delayed probe list.
  */
 struct funnel_drvdata {
 	void __iomem		*base;
@@ -51,6 +56,8 @@ struct funnel_drvdata {
 	unsigned long		priority;
 	raw_spinlock_t		spinlock;
 	struct cpumask		*cpumask;
+	struct device		*dev;
+	struct list_head	link;
 };
 
 struct funnel_smp_arg {
@@ -372,7 +379,7 @@ static int funnel_probe(struct device *dev, struct resource *res)
 		drvdata->cpumask = funnel_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,
@@ -380,10 +387,15 @@ static int funnel_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, &funnel_delay_probe);
+			cpus_read_unlock();
 			return 0;
+		}
+
+		cpus_read_unlock();
 	} else if (res) {
 		funnel_clear_self_claim_tag(drvdata);
 	}
@@ -395,9 +407,12 @@ static int funnel_remove(struct device *dev)
 {
 	struct funnel_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;
 }
 
@@ -535,8 +550,41 @@ static struct amba_driver dynamic_funnel_driver = {
 	.id_table	= dynamic_funnel_ids,
 };
 
+static int funnel_online_cpu(unsigned int cpu)
+{
+	struct funnel_drvdata *drvdata, *tmp;
+	int ret;
+
+	list_for_each_entry_safe(drvdata, tmp, &funnel_delay_probe, link) {
+		if (cpumask_test_cpu(cpu, drvdata->cpumask)) {
+			scoped_guard(spinlock,  &delay_lock)
+				list_del(&drvdata->link);
+
+			ret = pm_runtime_resume_and_get(drvdata->dev);
+			if (ret < 0)
+				return 0;
+
+			funnel_clear_self_claim_tag(drvdata);
+			funnel_add_coresight_dev(drvdata->dev);
+			pm_runtime_put(drvdata->dev);
+		}
+	}
+	return 0;
+}
+
 static int __init funnel_init(void)
 {
+	int ret;
+
+	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+					"arm/coresight-funnel:online",
+					funnel_online_cpu, NULL);
+
+	if (ret > 0)
+		hp_online = ret;
+	else
+		return ret;
+
 	return coresight_init_driver("funnel", &dynamic_funnel_driver, &funnel_driver,
 				     THIS_MODULE);
 }
@@ -544,6 +592,10 @@ static int __init funnel_init(void)
 static void __exit funnel_exit(void)
 {
 	coresight_remove_driver(&dynamic_funnel_driver, &funnel_driver);
+	if (hp_online) {
+		cpuhp_remove_state_nocalls(hp_online);
+		hp_online = 0;
+	}
 }
 
 module_init(funnel_init);

-- 
2.34.1