diff mbox series

[RFC,v2,09/35] LoongArch: Switch over to GENERIC_CPU_DEVICES

Message ID 20230913163823.7880-10-james.morse@arm.com (mailing list archive)
State Handled Elsewhere, archived
Headers show
Series ACPI/arm64: add support for virtual cpuhotplug | expand

Commit Message

James Morse Sept. 13, 2023, 4:37 p.m. UTC
Now that GENERIC_CPU_DEVICES calls arch_register_cpu(), which can be
overridden by the arch code, switch over to this to allow common code
to choose when the register_cpu() call is made.

This allows topology_init() to be removed.

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.

Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/loongarch/Kconfig           |  1 +
 arch/loongarch/kernel/topology.c | 29 ++---------------------------
 2 files changed, 3 insertions(+), 27 deletions(-)

Comments

Russell King (Oracle) Sept. 14, 2023, 10:03 a.m. UTC | #1
On Wed, Sep 13, 2023 at 04:37:57PM +0000, James Morse wrote:
> Now that GENERIC_CPU_DEVICES calls arch_register_cpu(), which can be
> overridden by the arch code, switch over to this to allow common code
> to choose when the register_cpu() call is made.
> 
> This allows topology_init() to be removed.
> 
> 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.
> 
> Signed-off-by: James Morse <james.morse@arm.com>

Same comment as x86 (moving the point at which cpus are registered
ought to be mentioned in the commit message.)
Jonathan Cameron Sept. 14, 2023, 11:47 a.m. UTC | #2
On Wed, 13 Sep 2023 16:37:57 +0000
James Morse <james.morse@arm.com> wrote:

> Now that GENERIC_CPU_DEVICES calls arch_register_cpu(), which can be
> overridden by the arch code, switch over to this to allow common code
> to choose when the register_cpu() call is made.
> 
> This allows topology_init() to be removed.
> 
> 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.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
>  arch/loongarch/Kconfig           |  1 +
>  arch/loongarch/kernel/topology.c | 29 ++---------------------------
>  2 files changed, 3 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 2bddd202470e..5bed51adc68c 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -72,6 +72,7 @@ config LOONGARCH
>  	select GENERIC_CLOCKEVENTS
>  	select GENERIC_CMOS_UPDATE
>  	select GENERIC_CPU_AUTOPROBE
> +	select GENERIC_CPU_DEVICES
>  	select GENERIC_ENTRY
>  	select GENERIC_GETTIMEOFDAY
>  	select GENERIC_IOREMAP if !ARCH_IOREMAP
> diff --git a/arch/loongarch/kernel/topology.c b/arch/loongarch/kernel/topology.c
> index caa7cd859078..8e4441c1ff39 100644
> --- a/arch/loongarch/kernel/topology.c
> +++ b/arch/loongarch/kernel/topology.c
> @@ -7,20 +7,13 @@
>  #include <linux/percpu.h>
>  #include <asm/bootinfo.h>
>  
> -static DEFINE_PER_CPU(struct cpu, cpu_devices);
> -
>  #ifdef CONFIG_HOTPLUG_CPU
>  int arch_register_cpu(int cpu)
>  {
> -	int ret;
>  	struct cpu *c = &per_cpu(cpu_devices, cpu);
>  
> -	c->hotpluggable = 1;

This is a bit subtle.  Can loongarch hotplug a CPU that
is also io_master(cpu)?  I have no idea if there is a subtle difference
between.

1) CPUs present at boot where if they are an io_master they are not allowed
   to be hot removed.
2) CPUs that turn up (hotplugged) later which are an io_master and by original code
   can be removed.

My guess is that no io_master CPU can be hotplugged in making this irrelevant
and your code correct as the =1 is just a micro optimizatoin.

If we can confirm that, a one line addition to the patch description would be
great. 

Otherwise LGTM

> -	ret = register_cpu(c, cpu);
> -	if (ret < 0)
> -		pr_warn("register_cpu %d failed (%d)\n", cpu, ret);
> -
> -	return ret;
> +	c->hotpluggable = !io_master(cpu);
> +	return register_cpu(c, cpu);
>  }
>  EXPORT_SYMBOL(arch_register_cpu);
>  
> @@ -33,21 +26,3 @@ void arch_unregister_cpu(int cpu)
>  }
>  EXPORT_SYMBOL(arch_unregister_cpu);
>  #endif
> -
> -static int __init topology_init(void)
> -{
> -	int i, ret;
> -
> -	for_each_present_cpu(i) {
> -		struct cpu *c = &per_cpu(cpu_devices, i);
> -
> -		c->hotpluggable = !io_master(i);
> -		ret = register_cpu(c, i);
> -		if (ret < 0)
> -			pr_warn("topology_init: register_cpu %d failed (%d)\n", i, ret);
> -	}
> -
> -	return 0;
> -}
> -
> -subsys_initcall(topology_init);
diff mbox series

Patch

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 2bddd202470e..5bed51adc68c 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -72,6 +72,7 @@  config LOONGARCH
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_CMOS_UPDATE
 	select GENERIC_CPU_AUTOPROBE
+	select GENERIC_CPU_DEVICES
 	select GENERIC_ENTRY
 	select GENERIC_GETTIMEOFDAY
 	select GENERIC_IOREMAP if !ARCH_IOREMAP
diff --git a/arch/loongarch/kernel/topology.c b/arch/loongarch/kernel/topology.c
index caa7cd859078..8e4441c1ff39 100644
--- a/arch/loongarch/kernel/topology.c
+++ b/arch/loongarch/kernel/topology.c
@@ -7,20 +7,13 @@ 
 #include <linux/percpu.h>
 #include <asm/bootinfo.h>
 
-static DEFINE_PER_CPU(struct cpu, cpu_devices);
-
 #ifdef CONFIG_HOTPLUG_CPU
 int arch_register_cpu(int cpu)
 {
-	int ret;
 	struct cpu *c = &per_cpu(cpu_devices, cpu);
 
-	c->hotpluggable = 1;
-	ret = register_cpu(c, cpu);
-	if (ret < 0)
-		pr_warn("register_cpu %d failed (%d)\n", cpu, ret);
-
-	return ret;
+	c->hotpluggable = !io_master(cpu);
+	return register_cpu(c, cpu);
 }
 EXPORT_SYMBOL(arch_register_cpu);
 
@@ -33,21 +26,3 @@  void arch_unregister_cpu(int cpu)
 }
 EXPORT_SYMBOL(arch_unregister_cpu);
 #endif
-
-static int __init topology_init(void)
-{
-	int i, ret;
-
-	for_each_present_cpu(i) {
-		struct cpu *c = &per_cpu(cpu_devices, i);
-
-		c->hotpluggable = !io_master(i);
-		ret = register_cpu(c, i);
-		if (ret < 0)
-			pr_warn("topology_init: register_cpu %d failed (%d)\n", i, ret);
-	}
-
-	return 0;
-}
-
-subsys_initcall(topology_init);