[PATCH v6 0/3] arm64: topology: Handle AMU FIE setup on CPU hotplug

[zhenglifeng (A)]

On 2025/12/1 23:27, Beata Michalska wrote:
> Hi,
> 
> Apologies for the delay in reviewing this - currently in progress....
> Out of curiosity: what's the cpufreq driver used for testing this series ?

I used cppc_cpufreq for testing this. But with some modifications in
processor_driver.c, or you'll find that the driver will fail to load with
maxcpus set. The modification below is only a temporary solution. I'm still
working on that.

---
diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index 5d824435b26b..2f286a1b0b02 100644
--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -33,6 +33,7 @@ MODULE_AUTHOR("Paul Diefenbaugh");
 MODULE_DESCRIPTION("ACPI Processor Driver");
 MODULE_LICENSE("GPL");
 
+static int acpi_processor_start(struct device *dev);
 static int acpi_processor_stop(struct device *dev);
 
 static const struct acpi_device_id processor_device_ids[] = {
@@ -46,6 +47,7 @@ static struct device_driver acpi_processor_driver = {
 	.name = "processor",
 	.bus = &cpu_subsys,
 	.acpi_match_table = processor_device_ids,
+	.probe = acpi_processor_start,
 	.remove = acpi_processor_stop,
 };
 
@@ -191,6 +193,21 @@ static int __acpi_processor_start(struct acpi_device *device)
 	return result;
 }
 
+static int acpi_processor_start(struct device *dev)
+{
+	struct acpi_device *device = ACPI_COMPANION(dev);
+	int ret;
+
+	if (!device)
+		return -ENODEV;
+
+	/* Protect against concurrent CPU hotplug operations */
+	cpu_hotplug_disable();
+	ret = __acpi_processor_start(device);
+	cpu_hotplug_enable();
+	return ret;
+}
+
 static int acpi_processor_stop(struct device *dev)
 {
 	struct acpi_device *device = ACPI_COMPANION(dev);
@@ -264,9 +281,9 @@ static int __init acpi_processor_driver_init(void)
 
 	acpi_processor_register_idle_driver();
 
-	result = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
-				   "acpi/cpu-drv:online",
-				   acpi_soft_cpu_online, NULL);
+	result = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+					   "acpi/cpu-drv:online",
+					   acpi_soft_cpu_online, NULL);
 	if (result < 0)
 		goto err;
 	hp_online = result;

> 
> ---
> BR
> Beata
> On Wed, Nov 19, 2025 at 04:13:53PM +0800, Lifeng Zheng wrote:
>> Solve a problem that causes CPUs Setup AMU FIE failed in a corner case,
>> even though they're eligible.
>>
>>
>