linux-kernel - Re: [PATCH RFC 21/22] riscv: Switch over to GENERIC_CPU

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Message-ID: <mhng-6d9a28af-d626-410e-913f-33bc01890537@palmer-ri-x1c9>
Date:   Tue, 07 Nov 2023 09:48:07 -0800 (PST)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     rmk+kernel@...linux.org.uk
CC:     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,
        x86@...nel.org, linux-csky@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-parisc@...r.kernel.org, salil.mehta@...wei.com,
        jean-philippe@...aro.org, jianyong.wu@....com, justin.he@....com,
        james.morse@....com, Paul Walmsley <paul.walmsley@...ive.com>,
        aou@...s.berkeley.edu
Subject:     Re: [PATCH RFC 21/22] riscv: Switch over to GENERIC_CPU_DEVICES

On Tue, 07 Nov 2023 02:31:06 PST (-0800), rmk+kernel@...linux.org.uk wrote:
> From: James Morse <james.morse@....com>
>
> 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.
>
> 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@....com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> ---
> Changes since RFC v2:
>  * Add note about initialisation order change.
> ---
>  arch/riscv/Kconfig        |  1 +
>  arch/riscv/kernel/setup.c | 19 ++++---------------
>  2 files changed, 5 insertions(+), 15 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index eaa15a20e6ae..264aa466aec3 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -69,6 +69,7 @@ config RISCV
>  	select GENERIC_ARCH_TOPOLOGY
>  	select GENERIC_ATOMIC64 if !64BIT
>  	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
> +	select GENERIC_CPU_DEVICES
>  	select GENERIC_EARLY_IOREMAP
>  	select GENERIC_ENTRY
>  	select GENERIC_GETTIMEOFDAY if HAVE_GENERIC_VDSO
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index 0624f44d43ec..f8875ae1b0aa 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -50,7 +50,6 @@ atomic_t hart_lottery __section(".sdata")
>  #endif
>  ;
>  unsigned long boot_cpu_hartid;
> -static DEFINE_PER_CPU(struct cpu, cpu_devices);
>
>  /*
>   * Place kernel memory regions on the resource tree so that
> @@ -295,23 +294,13 @@ void __init setup_arch(char **cmdline_p)
>  	riscv_set_dma_cache_alignment();
>  }
>
> -static int __init topology_init(void)
> +int arch_register_cpu(int cpu)
>  {
> -	int i, ret;
> +	struct cpu *c = &per_cpu(cpu_devices, cpu);
>
> -	for_each_possible_cpu(i) {
> -		struct cpu *cpu = &per_cpu(cpu_devices, i);
> -
> -		cpu->hotpluggable = cpu_has_hotplug(i);
> -		ret = register_cpu(cpu, i);
> -		if (unlikely(ret))
> -			pr_warn("Warning: %s: register_cpu %d failed (%d)\n",
> -			       __func__, i, ret);
> -	}
> -
> -	return 0;
> +	c->hotpluggable = cpu_has_hotplug(cpu);
> +	return register_cpu(c, cpu);
>  }
> -subsys_initcall(topology_init);
>
>  void free_initmem(void)
>  {

Acked-by: Palmer Dabbelt <palmer@...osinc.com>