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

From: achin.gupta@arm.com (Achin Gupta)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 06/16] ARM: b.L: generic SMP secondary bringup and hotplug support
Date: Mon, 14 Jan 2013 18:05:10 +0000	[thread overview]
Message-ID: <CAMpgmWCxQMoncnMqy_bzB+mBU7eGO_L4fR+Q5uMaxdFn4mL5PA@mail.gmail.com> (raw)
In-Reply-To: <50F053BF.8090302@ti.com>

Hi Santosh,

On Fri, Jan 11, 2013 at 6:02 PM, Santosh Shilimkar
<santosh.shilimkar@ti.com> wrote:
> On Thursday 10 January 2013 05:50 AM, 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.
>>
>> Signed-off-by: Nicolas Pitre <nico@linaro.org>
>> ---
>>   arch/arm/common/Makefile     |  2 +-
>>   arch/arm/common/bL_platsmp.c | 79
>> ++++++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 80 insertions(+), 1 deletion(-)
>>   create mode 100644 arch/arm/common/bL_platsmp.c
>>
>> diff --git a/arch/arm/common/Makefile b/arch/arm/common/Makefile
>> index 894c2ddf9b..59b36db7cc 100644
>> --- a/arch/arm/common/Makefile
>> +++ b/arch/arm/common/Makefile
>> @@ -15,4 +15,4 @@ obj-$(CONFIG_PCI_HOST_ITE8152)  += it8152.o
>>   obj-$(CONFIG_ARM_TIMER_SP804) += timer-sp.o
>>   obj-$(CONFIG_FIQ_GLUE)                += fiq_glue.o fiq_glue_setup.o
>>   obj-$(CONFIG_FIQ_DEBUGGER)    += fiq_debugger.o
>> -obj-$(CONFIG_BIG_LITTLE)       += bL_head.o bL_entry.o vlock.o
>> +obj-$(CONFIG_BIG_LITTLE)       += bL_head.o bL_entry.o bL_platsmp.o
>> vlock.o
>> 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;
>> +       pr_debug("%s: logical CPU %d is physical CPU %d cluster %d\n",
>> +                __func__, cpu, pcpu, pcluster);
>> +
>> +       bL_set_entry_vector(pcpu, pcluster, NULL);
>> +       ret = bL_cpu_power_up(pcpu, pcluster);
>> +       if (ret)
>> +               return ret;
>> +       bL_set_entry_vector(pcpu, pcluster, secondary_startup);
>> +       gic_raise_softirq(cpumask_of(cpu), 0);
>> +       sev();
>
> softirq() should be enough to break a CPU if it is in standby with
> wfe state. Is that additional sev() needed here ?

Not if the target cpu has its I & F bits disabled and that would be the
case with a secondary waiting to be woken up

thanks,
Achin

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