linux-kernel - [RFC PATCH v2 24/35] drivers: base: Implement weak arch_unregister

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Message-Id: <20230913163823.7880-25-james.morse@arm.com>
Date:   Wed, 13 Sep 2023 16:38:12 +0000
From:   James Morse <james.morse@....com>
To:     linux-pm@...r.kernel.org, loongarch@...ts.linux.dev,
        linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, kvmarm@...ts.linux.dev
Cc:     x86@...nel.org, Salil Mehta <salil.mehta@...wei.com>,
        Russell King <linux@...linux.org.uk>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        jianyong.wu@....com, justin.he@....com
Subject: [RFC PATCH v2 24/35] drivers: base: Implement weak arch_unregister_cpu()

Add arch_unregister_cpu() to allow the ACPI machinery to call
unregister_cpu(). This is enough for arm64, riscv and loongarch, but
needs to be overridden by x86 and ia64 who need to do more work.

CC: Jean-Philippe Brucker <jean-philippe@...aro.org>
Signed-off-by: James Morse <james.morse@....com>
---
Changes since v1:
 * Added CONFIG_HOTPLUG_CPU ifdeffery around unregister_cpu
---
 arch/ia64/include/asm/cpu.h      | 4 ----
 arch/loongarch/include/asm/cpu.h | 6 ------
 arch/x86/include/asm/cpu.h       | 1 -
 drivers/base/cpu.c               | 9 ++++++++-
 4 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/arch/ia64/include/asm/cpu.h b/arch/ia64/include/asm/cpu.h
index a3e690e685e5..642d71675ddb 100644
--- a/arch/ia64/include/asm/cpu.h
+++ b/arch/ia64/include/asm/cpu.h
@@ -15,8 +15,4 @@ DECLARE_PER_CPU(struct ia64_cpu, cpu_devices);
 
 DECLARE_PER_CPU(int, cpu_state);
 
-#ifdef CONFIG_HOTPLUG_CPU
-extern void arch_unregister_cpu(int);
-#endif
-
 #endif /* _ASM_IA64_CPU_H_ */
diff --git a/arch/loongarch/include/asm/cpu.h b/arch/loongarch/include/asm/cpu.h
index b8568e637420..48b9f7168bcc 100644
--- a/arch/loongarch/include/asm/cpu.h
+++ b/arch/loongarch/include/asm/cpu.h
@@ -128,10 +128,4 @@ enum cpu_type_enum {
 #define LOONGARCH_CPU_HYPERVISOR	BIT_ULL(CPU_FEATURE_HYPERVISOR)
 #define LOONGARCH_CPU_PTW		BIT_ULL(CPU_FEATURE_PTW)
 
-#if !defined(__ASSEMBLY__)
-#ifdef CONFIG_HOTPLUG_CPU
-void arch_unregister_cpu(int cpu);
-#endif
-#endif /* ! __ASSEMBLY__ */
-
 #endif /* _ASM_CPU_H */
diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index f349c94510e8..91867a6a9f8e 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -24,7 +24,6 @@ static inline void prefill_possible_map(void) {}
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_HOTPLUG_CPU
-extern void arch_unregister_cpu(int);
 extern void soft_restart_cpu(void);
 #endif
 
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 677f963e02ce..c709747c4a18 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -531,7 +531,14 @@ int __weak arch_register_cpu(int cpu)
 {
 	return register_cpu(&per_cpu(cpu_devices, cpu), cpu);
 }
-#endif
+
+#ifdef CONFIG_HOTPLUG_CPU
+void __weak arch_unregister_cpu(int num)
+{
+	unregister_cpu(&per_cpu(cpu_devices, num));
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+#endif /* CONFIG_GENERIC_CPU_DEVICES */
 
 static void __init cpu_dev_register_generic(void)
 {
-- 
2.39.2