linux-kernel - [PATCH] ACPI: processor: Add acpi_processor_start() back to parse

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Message-ID: <20260120113242.3843463-1-zhenglifeng1@huawei.com>
Date: Tue, 20 Jan 2026 19:32:42 +0800
From: Lifeng Zheng <zhenglifeng1@...wei.com>
To: <rafael@...nel.org>, <catalin.marinas@....com>,
	<Jonathan.Cameron@...wei.com>, <lenb@...nel.org>
CC: <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linuxarm@...wei.com>, <gshan@...hat.com>, <miguel.luis@...cle.com>,
	<guohanjun@...wei.com>, <zhanjie9@...ilicon.com>, <lihuisong@...wei.com>,
	<yubowen8@...wei.com>, <zhangpengjie2@...wei.com>, <wangzhi12@...wei.com>,
	<linhongye@...artners.com>, <zhenglifeng1@...wei.com>
Subject: [PATCH] ACPI: processor: Add acpi_processor_start() back to parse _CPC tables before CPU online

Currently, if boot with maxcpus less than NR_CPUS, the cppc_cpufreq driver
will fail to register. Because it requires the domain information of all
possible CPUs to construct shared_cpu_map, which shows the CPUs that share
the same domain.

Commit c1385c1f0ba3 ("ACPI: processor: Simplify initial onlining to use
same path for cold and hotplug") removes probe() of acpi_processor_driver
and makes acpi_cppc_processor_probe() only being called the first time CPU
goes online. This means that CPUs that haven't yet gone online will not
have pre-parsed _CPC objects and causes cppc_cpufreq driver register fail.

Add acpi_processor_start() back as the probe() callback of
acpi_processor_driver and call acpi_cppc_processor_probe() in it to make
sure all _CPC tables will be parsed when acpi_processor_driver registered.

Fixes: c1385c1f0ba3 ("ACPI: processor: Simplify initial onlining to use same path for cold and hotplug")
Signed-off-by: Lifeng Zheng <zhenglifeng1@...wei.com>
---
 drivers/acpi/processor_driver.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index 65e779be64ff..c8b4daf580b0 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,
 };
 
@@ -162,10 +164,6 @@ static int __acpi_processor_start(struct acpi_device *device)
 	if (!pr)
 		return -ENODEV;
 
-	result = acpi_cppc_processor_probe(pr);
-	if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
-		dev_dbg(&device->dev, "CPPC data invalid or not present\n");
-
 	if (!cpuidle_get_driver() || cpuidle_get_driver() == &acpi_idle_driver)
 		acpi_processor_power_init(pr);
 
@@ -192,6 +190,30 @@ 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);
+	struct acpi_processor *pr;
+	int result;
+
+	if (!device)
+		return -ENODEV;
+
+	pr = acpi_driver_data(device);
+	if (!pr)
+		return -ENODEV;
+
+	/* Protect against concurrent CPU hotplug operations */
+	cpu_hotplug_disable();
+	result = acpi_cppc_processor_probe(pr);
+	cpu_hotplug_enable();
+
+	if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
+		dev_dbg(&device->dev, "CPPC data invalid or not present\n");
+
+	return 0;
+}
+
 static int acpi_processor_stop(struct device *dev)
 {
 	struct acpi_device *device = ACPI_COMPANION(dev);
-- 
2.33.0