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From:   Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
To:     linux-pm@vger.kernel.org, loongarch@lists.linux.dev,
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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 12/39] ia64/topology: Switch over to GENERIC_CPU_DEVICES
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Date:   Tue, 24 Oct 2023 16:17:11 +0100
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From: James Morse <james.morse@arm.com>

ia64 has its own arch specific data structure for cpus: struct ia64_cpu.
This has one member, making ia64's cpu_devices the same as that
provided be GENERIC_CPU_DEVICES.
ia64 craetes a percpu struct ia64_cpu called cpu_devices, which has no
users. Instead it uses the struct ia64_cpu named sysfs_cpus allocated at
boot.

Remove the arch specific structure allocation and initialisation.
ia64's arch_register_cpu() now overrides the weak version from
GENERIC_CPU_DEVICES, and uses the percpu cpu_devices defined by
core code.

All uses of sysfs_cpus are changed to use the percpu cpu_devices.

This is an intermediate step to the logic being moved to drivers/acpi,
where GENERIC_CPU_DEVICES will do the work when booting with acpi=off.

This patch also has the effect of moving the registration of CPUs from
subsys to driver core initialisation, prior to any initcalls running.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
Changes since RFC v2:
 * Add note about initialisation order change.
---
 arch/ia64/Kconfig           |  1 +
 arch/ia64/include/asm/cpu.h |  6 ------
 arch/ia64/kernel/topology.c | 35 +++++------------------------------
 3 files changed, 6 insertions(+), 36 deletions(-)

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index a3bfd42467ab..06692e1c7c62 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -42,6 +42,7 @@ config IA64
 	select HAVE_FUNCTION_DESCRIPTORS
 	select HAVE_VIRT_CPU_ACCOUNTING
 	select HUGETLB_PAGE_SIZE_VARIABLE if HUGETLB_PAGE
+	select GENERIC_CPU_DEVICES
 	select GENERIC_IRQ_PROBE
 	select GENERIC_PENDING_IRQ if SMP
 	select GENERIC_IRQ_SHOW
diff --git a/arch/ia64/include/asm/cpu.h b/arch/ia64/include/asm/cpu.h
index 642d71675ddb..3b36c6a382bb 100644
--- a/arch/ia64/include/asm/cpu.h
+++ b/arch/ia64/include/asm/cpu.h
@@ -7,12 +7,6 @@
 #include <linux/topology.h>
 #include <linux/percpu.h>
 
-struct ia64_cpu {
-	struct cpu cpu;
-};
-
-DECLARE_PER_CPU(struct ia64_cpu, cpu_devices);
-
 DECLARE_PER_CPU(int, cpu_state);
 
 #endif /* _ASM_IA64_CPU_H_ */
diff --git a/arch/ia64/kernel/topology.c b/arch/ia64/kernel/topology.c
index 741863a187a6..8f5cafde2bc9 100644
--- a/arch/ia64/kernel/topology.c
+++ b/arch/ia64/kernel/topology.c
@@ -26,8 +26,6 @@
 #include <asm/numa.h>
 #include <asm/cpu.h>
 
-static struct ia64_cpu *sysfs_cpus;
-
 void arch_fix_phys_package_id(int num, u32 slot)
 {
 #ifdef CONFIG_SMP
@@ -41,50 +39,27 @@ EXPORT_SYMBOL_GPL(arch_fix_phys_package_id);
 #ifdef CONFIG_HOTPLUG_CPU
 int __ref arch_register_cpu(int num)
 {
+	struct cpu *cpu = &per_cpu(cpu_devices, num);
+
 	/*
 	 * If CPEI can be re-targeted or if this is not
 	 * CPEI target, then it is hotpluggable
 	 */
 	if (can_cpei_retarget() || !is_cpu_cpei_target(num))
-		sysfs_cpus[num].cpu.hotpluggable = 1;
+		cpu->hotpluggable = 1;
 	map_cpu_to_node(num, node_cpuid[num].nid);
-	return register_cpu(&sysfs_cpus[num].cpu, num);
+	return register_cpu(cpu, num);
 }
 EXPORT_SYMBOL(arch_register_cpu);
 
 void __ref arch_unregister_cpu(int num)
 {
-	unregister_cpu(&sysfs_cpus[num].cpu);
+	unregister_cpu(&per_cpu(cpu_devices, num));
 	unmap_cpu_from_node(num, cpu_to_node(num));
 }
 EXPORT_SYMBOL(arch_unregister_cpu);
-#else
-int __init arch_register_cpu(int num)
-{
-	return register_cpu(&sysfs_cpus[num].cpu, num);
-}
 #endif /*CONFIG_HOTPLUG_CPU*/
 
-
-static int __init topology_init(void)
-{
-	int i, err = 0;
-
-	sysfs_cpus = kcalloc(NR_CPUS, sizeof(struct ia64_cpu), GFP_KERNEL);
-	if (!sysfs_cpus)
-		panic("kzalloc in topology_init failed - NR_CPUS too big?");
-
-	for_each_present_cpu(i) {
-		if((err = arch_register_cpu(i)))
-			goto out;
-	}
-out:
-	return err;
-}
-
-subsys_initcall(topology_init);
-
-
 /*
  * Export cpu cache information through sysfs
  */
-- 
2.30.2