[PATCHv3 5/5] arm64: add PSCI CPU_OFF-based hotplug support

[Nicolas Pitre]

On Wed, 14 Aug 2013, Mark Rutland wrote:

> This patch adds support for using PSCI CPU_OFF calls for CPU hotplug.
> With this code it is possible to hot unplug CPUs with "psci" as their
> boot-method, as long as there's an appropriate cpu_off function id
> specified in the psci node.
> 
> Signed-off-by: Mark Rutland <mark.rutland at arm.com>

Acked-by: Nicolas Pitre <nico at linaro.org>


> ---
>  arch/arm64/kernel/smp_psci.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/arch/arm64/kernel/smp_psci.c b/arch/arm64/kernel/smp_psci.c
> index 20499bc..e9e5890 100644
> --- a/arch/arm64/kernel/smp_psci.c
> +++ b/arch/arm64/kernel/smp_psci.c
> @@ -47,9 +47,39 @@ static int smp_psci_cpu_boot(unsigned int cpu)
>  	return err;
>  }
>  
> +#ifdef CONFIG_HOTPLUG_CPU
> +static int smp_psci_cpu_disable(unsigned int cpu)
> +{
> +	/* Fail early if we don't have CPU_OFF support */
> +	if (!psci_ops.cpu_off)
> +		return -EOPNOTSUPP;
> +	return 0;
> +}
> +
> +static void smp_psci_cpu_die(unsigned int cpu)
> +{
> +	int ret;
> +	/*
> +	 * There are no known implementations of PSCI actually using the
> +	 * power state field, pass a sensible default for now.
> +	 */
> +	struct psci_power_state state = {
> +		.type = PSCI_POWER_STATE_TYPE_POWER_DOWN,
> +	};
> +
> +	ret = psci_ops.cpu_off(state);
> +
> +	pr_crit("psci: unable to power off CPU%u (%d)\n", cpu, ret);
> +}
> +#endif
> +
>  const struct smp_operations smp_psci_ops = {
>  	.name		= "psci",
>  	.cpu_init	= smp_psci_cpu_init,
>  	.cpu_prepare	= smp_psci_cpu_prepare,
>  	.cpu_boot	= smp_psci_cpu_boot,
> +#ifdef CONFIG_HOTPLUG_CPU
> +	.cpu_disable	= smp_psci_cpu_disable,
> +	.cpu_die	= smp_psci_cpu_die,
> +#endif
>  };
> -- 
> 1.8.1.1
>