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From:   Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
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Cc:     Salil Mehta <salil.mehta@huawei.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        jianyong.wu@arm.com, justin.he@arm.com,
        James Morse <james.morse@arm.com>
Subject: [PATCH RFC v3 04/21] ACPI: processor: Register all CPUs from
 acpi_processor_get_info()
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Sender: Russell King <rmk@armlinux.org.uk>
Date:   Wed, 13 Dec 2023 12:49:31 +0000
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From: James Morse <james.morse@arm.com>

To allow ACPI to skip the call to arch_register_cpu() when the _STA
value indicates the CPU can't be brought online right now, move the
arch_register_cpu() call into acpi_processor_get_info().

Systems can still be booted with 'acpi=off', or not include an
ACPI description at all. For these, the CPUs continue to be
registered by cpu_dev_register_generic().

This moves the CPU register logic back to a subsys_initcall(),
while the memory nodes will have been registered earlier.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Tested-by: Miguel Luis <miguel.luis@oracle.com>
Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
Tested-by: Jianyong Wu <jianyong.wu@arm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
Changes since RFC v2:
 * Fixup comment in acpi_processor_get_info() (Gavin Shan)
 * Add comment in cpu_dev_register_generic() (Gavin Shan)
---
 drivers/acpi/acpi_processor.c | 12 ++++++++++++
 drivers/base/cpu.c            |  6 +++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index 0511f2bc10bc..e7ed4730cbbe 100644
--- a/drivers/acpi/acpi_processor.c
+++ b/drivers/acpi/acpi_processor.c
@@ -314,6 +314,18 @@ static int acpi_processor_get_info(struct acpi_device *device)
 			cpufreq_add_device("acpi-cpufreq");
 	}
 
+	/*
+	 * Register CPUs that are present. get_cpu_device() is used to skip
+	 * duplicate CPU descriptions from firmware.
+	 */
+	if (!invalid_logical_cpuid(pr->id) && cpu_present(pr->id) &&
+	    !get_cpu_device(pr->id)) {
+		int ret = arch_register_cpu(pr->id);
+
+		if (ret)
+			return ret;
+	}
+
 	/*
 	 *  Extra Processor objects may be enumerated on MP systems with
 	 *  less than the max # of CPUs. They should be ignored _iff
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 47de0f140ba6..13d052bf13f4 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -553,7 +553,11 @@ static void __init cpu_dev_register_generic(void)
 {
 	int i, ret;
 
-	if (!IS_ENABLED(CONFIG_GENERIC_CPU_DEVICES))
+	/*
+	 * When ACPI is enabled, CPUs are registered via
+	 * acpi_processor_get_info().
+	 */
+	if (!IS_ENABLED(CONFIG_GENERIC_CPU_DEVICES) || !acpi_disabled)
 		return;
 
 	for_each_present_cpu(i) {
-- 
2.30.2