On Wed, 13 Sep 2023 16:37:57 +0000
James Morse <james.morse@xxxxxxx> 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@xxxxxxx>
> ---
> 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);
