linux-kernel - Re: [RFC PATCH v2] Add IPI entry for CPU UP

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Date:	Tue, 12 Jan 2016 10:17:42 +0800
From:	Zhaoyang Huang <zhaoyang.huang@...aro.org>
To:	Zhaoyang Huang (黄朝阳) 
	<zhaoyang.huang@...eadtrum.com>,
	Catalin Marinas <catalin.marinas@....com>, will.deacon@....com,
	linux-kernel@...r.kernel.org,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Hanjun Guo <hanjun.guo@...aro.org>, suzuki.poulose@....com,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [RFC PATCH v2] Add IPI entry for CPU UP

On 12 January 2016 at 10:05, Zhaoyang Huang <zhaoyang.huang@...aro.org> wrote:
> In some ARM SOCs, IPI interrupt is used for hotplug in one cpu, that is,
> sending a IPI to the core in WFI and powerdown status. So Add a IPI
> entry for handle this kind of cpu up interrupt
> Launching the IPI can be done within PSCI, while there will be one unknown
> type of IPI as the dest core come up to the kernel world which will bring a
> warning so far.So add such type of IPI to handle the interrupt.
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...eadtrum.com>
> ---
>  arch/arm64/include/asm/hardirq.h |    2 +-
>  arch/arm64/kernel/smp.c          |   10 ++++++++++
>  2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/hardirq.h b/arch/arm64/include/asm/hardirq.h
> index a57601f..bb4edb7 100644
> --- a/arch/arm64/include/asm/hardirq.h
> +++ b/arch/arm64/include/asm/hardirq.h
> @@ -20,7 +20,7 @@
>  #include <linux/threads.h>
>  #include <asm/irq.h>
>
> -#define NR_IPI 5
> +#define NR_IPI   6
>
>  typedef struct {
>         unsigned int __softirq_pending;
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index b1adc51..20e63c9 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -70,6 +70,7 @@ enum ipi_msg_type {
>         IPI_CPU_STOP,
>         IPI_TIMER,
>         IPI_IRQ_WORK,
> +       IPI_CPU_UP,
>  };
>
>  /*
> @@ -627,6 +628,7 @@ static const char *ipi_types[NR_IPI] __tracepoint_string = {
>         S(IPI_CPU_STOP, "CPU stop interrupts"),
>         S(IPI_TIMER, "Timer broadcast interrupts"),
>         S(IPI_IRQ_WORK, "IRQ work interrupts"),
> +       S(IPI_CPU_UP, "Hotplug cpu up by ipi"),
>  };
>
>  static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
> @@ -746,6 +748,8 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
>                 irq_exit();
>                 break;
>  #endif
> +       case IPI_CPU_UP:
> +               break;
>
>         default:
>                 pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr);
> @@ -798,3 +802,9 @@ int setup_profiling_timer(unsigned int multiplier)
>  {
>         return -EINVAL;
>  }
> +
> +void smp_send_cpuup(int cpu)
> +{
> +       smp_cross_call(cpumask_of(cpu), IPI_CPU_UP);
> +}
> +
> --
> 1.7.9.5
>
As the added commit message saying, the IPI can be launched in either
of kernel or PSCI. But there will be a unknown type of IPI when dest
core come to the kernel.