[PATCH] cpufreq: qcom-hw: order driver state before registration

[Jaidev Shastri via B4 Relay]

From: Jaidev Shastri <jaidevshastri@xxxxxx>

qcom_cpufreq_hw_driver_probe() stores xo_rate, cpu_hw_rate,
qcom_cpufreq.soc_data and the per-domain qcom_cpufreq.data[] array with
plain stores and then calls cpufreq_register_driver(). The cpufreq core
invokes qcom_cpufreq_hw_cpu_init() for every policy, on other CPUs, and
that function reads all of them with plain loads.

Order the stores before the registration with smp_wmb() and add the
matching smp_rmb() in qcom_cpufreq_hw_cpu_init().

Found with MBCheck, a static herd7-based memory consistency checker.

Signed-off-by: Jaidev Shastri <jaidevshastri@xxxxxx>
---
 drivers/cpufreq/qcom-cpufreq-hw.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
index 874ff3fb9..62cc1f403 100644
--- a/drivers/cpufreq/qcom-cpufreq-hw.c
+++ b/drivers/cpufreq/qcom-cpufreq-hw.c
@@ -554,6 +554,8 @@ static int qcom_cpufreq_hw_cpu_init(struct cpufreq_policy *policy)
 		return ret;
 
 	index = args.args[0];
+	/* Pairs with the smp_wmb() before cpufreq_register_driver() in probe. */
+	smp_rmb();
 	data = &qcom_cpufreq.data[index];
 
 	/* HW should be in enabled state to proceed */
@@ -738,6 +740,13 @@ static int qcom_cpufreq_hw_driver_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	/*
+	 * qcom_cpufreq_hw_cpu_init() runs on other CPUs through the cpufreq
+	 * core once the driver is registered and reads xo_rate, cpu_hw_rate,
+	 * qcom_cpufreq.soc_data and qcom_cpufreq.data[]. Order those stores
+	 * before the registration. Pairs with the smp_rmb() in cpu_init.
+	 */
+	smp_wmb();
 	ret = cpufreq_register_driver(&cpufreq_qcom_hw_driver);
 	if (ret)
 		dev_err(dev, "CPUFreq HW driver failed to register\n");

---
base-commit: 93f51579e7df248780214094418f205253383cc5
change-id: 20260921-mb-qcom-cpufreq-42f15afbfa4f

Best regards,
--  
Jaidev Shastri <jaidevshastri@xxxxxx>