linux-kernel - [PATCH] cpufreq: scmi: Skip SCMI devices that aren't used by the CPUs

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Message-ID: <20250411212941.1275572-1-quic_mdtipton@quicinc.com>
Date: Fri, 11 Apr 2025 14:29:41 -0700
From: Mike Tipton <quic_mdtipton@...cinc.com>
To: Sudeep Holla <sudeep.holla@....com>,
        Cristian Marussi
	<cristian.marussi@....com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        "Viresh
 Kumar" <viresh.kumar@...aro.org>
CC: <arm-scmi@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Mike Tipton
	<quic_mdtipton@...cinc.com>
Subject: [PATCH] cpufreq: scmi: Skip SCMI devices that aren't used by the CPUs

Currently, all SCMI devices with performance domains attempt to register
a cpufreq driver, even if their performance domains aren't used to
control the CPUs. The cpufreq framework only supports registering a
single driver, so only the first device will succeed. And if that device
isn't used for the CPUs, then cpufreq will scale the wrong domains.

To avoid this, return early from scmi_cpufreq_probe() if the probing
SCMI device isn't referenced by the CPU device phandles.

This keeps the existing assumption that all CPUs are controlled by a
single SCMI device.

Signed-off-by: Mike Tipton <quic_mdtipton@...cinc.com>
---
 drivers/cpufreq/scmi-cpufreq.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
index 944e899eb1be..7981a879974b 100644
--- a/drivers/cpufreq/scmi-cpufreq.c
+++ b/drivers/cpufreq/scmi-cpufreq.c
@@ -393,6 +393,32 @@ static struct cpufreq_driver scmi_cpufreq_driver = {
 	.set_boost	= cpufreq_boost_set_sw,
 };
 
+static bool scmi_dev_used_by_cpus(struct device *scmi_dev)
+{
+	struct device_node *scmi_np = scmi_dev->of_node;
+	struct device_node *np;
+	struct device *cpu_dev;
+	int cpu, idx;
+
+	for_each_possible_cpu(cpu) {
+		cpu_dev = get_cpu_device(cpu);
+		if (!cpu_dev)
+			continue;
+
+		np = cpu_dev->of_node;
+
+		if (of_parse_phandle(np, "clocks", 0) == scmi_np)
+			return true;
+
+		idx = of_property_match_string(np, "power-domain-names", "perf");
+
+		if (of_parse_phandle(np, "power-domains", idx) == scmi_np)
+			return true;
+	}
+
+	return false;
+}
+
 static int scmi_cpufreq_probe(struct scmi_device *sdev)
 {
 	int ret;
@@ -404,6 +430,9 @@ static int scmi_cpufreq_probe(struct scmi_device *sdev)
 	if (!handle)
 		return -ENODEV;
 
+	if (!scmi_dev_used_by_cpus(dev))
+		return 0;
+
 	scmi_cpufreq_driver.driver_data = sdev;
 
 	perf_ops = handle->devm_protocol_get(sdev, SCMI_PROTOCOL_PERF, &ph);
-- 
2.34.1