[PATCH 06/16] ARM: b.L: generic SMP secondary bringup and hotplug support

[Will Deacon]

On Thu, Jan 10, 2013 at 12:20:41AM +0000, Nicolas Pitre wrote:
> Now that the b.L power API is in place, we can use it for SMP secondary
> bringup and CPU hotplug in a generic fashion.

[...]

> diff --git a/arch/arm/common/bL_platsmp.c b/arch/arm/common/bL_platsmp.c
> new file mode 100644
> index 0000000000..0acb9f4685
> --- /dev/null
> +++ b/arch/arm/common/bL_platsmp.c
> @@ -0,0 +1,79 @@
> +/*
> + * linux/arch/arm/mach-vexpress/bL_platsmp.c
> + *
> + * Created by:  Nicolas Pitre, November 2012
> + * Copyright:   (C) 2012  Linaro Limited
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * Code to handle secondary CPU bringup and hotplug for the bL power API.
> + */
> +
> +#include <linux/init.h>
> +#include <linux/smp.h>
> +
> +#include <asm/bL_entry.h>
> +#include <asm/smp_plat.h>
> +#include <asm/hardware/gic.h>
> +
> +static void __init simple_smp_init_cpus(void)
> +{
> +	set_smp_cross_call(gic_raise_softirq);
> +}
> +
> +static int __cpuinit bL_boot_secondary(unsigned int cpu, struct task_struct *idle)
> +{
> +	unsigned int pcpu, pcluster, ret;
> +	extern void secondary_startup(void);
> +
> +	pcpu = cpu_logical_map(cpu) & 0xff;
> +	pcluster = (cpu_logical_map(cpu) >> 8) & 0xff;

Again, you can probably use Lorenzo's helpers here.

> +	pr_debug("%s: logical CPU %d is physical CPU %d cluster %d\n",
> +		 __func__, cpu, pcpu, pcluster);
> +
> +	bL_set_entry_vector(pcpu, pcluster, NULL);

Now that you don't have a barrier in this function, you need one here.

> +	ret = bL_cpu_power_up(pcpu, pcluster);
> +	if (ret)
> +		return ret;

and here, although I confess to not understanding why you write NULL the
first time.

> +	bL_set_entry_vector(pcpu, pcluster, secondary_startup);
> +	gic_raise_softirq(cpumask_of(cpu), 0);
> +	sev();

This relise on the event register being able to be set if the target is in a
low-power (wfi) state. I'd feel safer with a dsb before the sev...

Will