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    Subject[tip:smp/hotplug] arm/twd: Convert to hotplug state machine
    Commit-ID:  26b8768868c090151aa8c337773d429e0d5ca727
    Gitweb: http://git.kernel.org/tip/26b8768868c090151aa8c337773d429e0d5ca727
    Author: Richard Cochran <rcochran@linutronix.de>
    AuthorDate: Wed, 13 Jul 2016 17:16:51 +0000
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Fri, 15 Jul 2016 10:40:28 +0200

    arm/twd: Convert to hotplug state machine

    Install the callbacks via the state machine. The callbacks won't be invoked on
    already online CPUs.

    Signed-off-by: Richard Cochran <rcochran@linutronix.de>
    Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
    Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
    Cc: Eric Anholt <eric@anholt.net>
    Cc: Felipe Balbi <balbi@ti.com>
    Cc: Heiko Stuebner <heiko@sntech.de>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Russell King <linux@arm.linux.org.uk>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Vineet Gupta <vgupta@synopsys.com>
    Cc: Viresh Kumar <viresh.kumar@linaro.org>
    Cc: linux-arm-kernel@lists.infradead.org
    Cc: rt@linutronix.de
    Link: http://lkml.kernel.org/r/20160713153336.881124821@linutronix.de
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/arm/kernel/smp_twd.c | 31 +++++++++++--------------------
    include/linux/cpuhotplug.h | 1 +
    2 files changed, 12 insertions(+), 20 deletions(-)

    diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
    index b6ec65e..02d5e5e 100644
    --- a/arch/arm/kernel/smp_twd.c
    +++ b/arch/arm/kernel/smp_twd.c
    @@ -310,24 +310,17 @@ static void twd_timer_setup(void)
    enable_percpu_irq(clk->irq, 0);
    }

    -static int twd_timer_cpu_notify(struct notifier_block *self,
    - unsigned long action, void *hcpu)
    +static int twd_timer_starting_cpu(unsigned int cpu)
    {
    - switch (action & ~CPU_TASKS_FROZEN) {
    - case CPU_STARTING:
    - twd_timer_setup();
    - break;
    - case CPU_DYING:
    - twd_timer_stop();
    - break;
    - }
    -
    - return NOTIFY_OK;
    + twd_timer_setup();
    + return 0;
    }

    -static struct notifier_block twd_timer_cpu_nb = {
    - .notifier_call = twd_timer_cpu_notify,
    -};
    +static int twd_timer_dying_cpu(unsigned int cpu)
    +{
    + twd_timer_stop();
    + return 0;
    +}

    static int __init twd_local_timer_common_register(struct device_node *np)
    {
    @@ -345,9 +338,9 @@ static int __init twd_local_timer_common_register(struct device_node *np)
    goto out_free;
    }

    - err = register_cpu_notifier(&twd_timer_cpu_nb);
    - if (err)
    - goto out_irq;
    + cpuhp_setup_state_nocalls(CPUHP_AP_ARM_TWD_STARTING,
    + "AP_ARM_TWD_STARTING",
    + twd_timer_starting_cpu, twd_timer_dying_cpu);

    twd_get_clock(np);
    if (!of_property_read_bool(np, "always-on"))
    @@ -365,8 +358,6 @@ static int __init twd_local_timer_common_register(struct device_node *np)

    return 0;

    -out_irq:
    - free_percpu_irq(twd_ppi, twd_evt);
    out_free:
    iounmap(twd_base);
    twd_base = NULL;
    diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
    index 2057e64..ad48881 100644
    --- a/include/linux/cpuhotplug.h
    +++ b/include/linux/cpuhotplug.h
    @@ -40,6 +40,7 @@ enum cpuhp_state {
    CPUHP_AP_ARM_L2X0_STARTING,
    CPUHP_AP_ARM_ARCH_TIMER_STARTING,
    CPUHP_AP_DUMMY_TIMER_STARTING,
    + CPUHP_AP_ARM_TWD_STARTING,
    CPUHP_AP_METAG_TIMER_STARTING,
    CPUHP_AP_QCOM_TIMER_STARTING,
    CPUHP_AP_MIPS_GIC_TIMER_STARTING,
    \
     
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