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    Subject[patch V2 23/67] bus/arm-ccn: Convert to hotplug statemachine
    From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

    Install the callbacks via the state machine and let the core invoke
    the callbacks on the already online CPUs.

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Cc: Dan Carpenter <dan.carpenter@oracle.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Pawel Moll <pawel.moll@arm.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
    ---
    drivers/bus/arm-ccn.c | 57 ++++++++++++++++++++++-----------------------
    include/linux/cpuhotplug.h | 1
    2 files changed, 29 insertions(+), 29 deletions(-)

    --- a/drivers/bus/arm-ccn.c
    +++ b/drivers/bus/arm-ccn.c
    @@ -167,7 +167,7 @@ struct arm_ccn_dt {
    struct hrtimer hrtimer;

    cpumask_t cpu;
    - struct notifier_block cpu_nb;
    + struct list_head entry;

    struct pmu pmu;
    };
    @@ -189,6 +189,8 @@ struct arm_ccn {
    struct arm_ccn_dt dt;
    };

    +static DEFINE_MUTEX(arm_ccn_mutex);
    +static LIST_HEAD(arm_ccn_list);

    static int arm_ccn_node_to_xp(int node)
    {
    @@ -1171,30 +1173,27 @@ static enum hrtimer_restart arm_ccn_pmu_
    }


    -static int arm_ccn_pmu_cpu_notifier(struct notifier_block *nb,
    - unsigned long action, void *hcpu)
    +static int arm_ccn_pmu_offline_cpu(unsigned int cpu)
    {
    - struct arm_ccn_dt *dt = container_of(nb, struct arm_ccn_dt, cpu_nb);
    - struct arm_ccn *ccn = container_of(dt, struct arm_ccn, dt);
    - unsigned int cpu = (long)hcpu; /* for (long) see kernel/cpu.c */
    + struct arm_ccn_dt *dt;
    unsigned int target;

    - switch (action & ~CPU_TASKS_FROZEN) {
    - case CPU_DOWN_PREPARE:
    + mutex_lock(&arm_ccn_mutex);
    + list_for_each_entry(dt, &arm_ccn_list, entry) {
    + struct arm_ccn *ccn = container_of(dt, struct arm_ccn, dt);
    +
    if (!cpumask_test_and_clear_cpu(cpu, &dt->cpu))
    - break;
    + continue;
    target = cpumask_any_but(cpu_online_mask, cpu);
    if (target >= nr_cpu_ids)
    - break;
    + continue;
    perf_pmu_migrate_context(&dt->pmu, cpu, target);
    cpumask_set_cpu(target, &dt->cpu);
    if (ccn->irq)
    WARN_ON(irq_set_affinity_hint(ccn->irq, &dt->cpu) != 0);
    - default:
    - break;
    }
    -
    - return NOTIFY_OK;
    + mutex_unlock(&arm_ccn_mutex);
    + return 0;
    }


    @@ -1266,16 +1265,6 @@ static int arm_ccn_pmu_init(struct arm_c
    /* Pick one CPU which we will use to collect data from CCN... */
    cpumask_set_cpu(smp_processor_id(), &ccn->dt.cpu);

    - /*
    - * ... and change the selection when it goes offline. Priority is
    - * picked to have a chance to migrate events before perf is notified.
    - */
    - ccn->dt.cpu_nb.notifier_call = arm_ccn_pmu_cpu_notifier;
    - ccn->dt.cpu_nb.priority = CPU_PRI_PERF + 1,
    - err = register_cpu_notifier(&ccn->dt.cpu_nb);
    - if (err)
    - goto error_cpu_notifier;
    -
    /* Also make sure that the overflow interrupt is handled by this CPU */
    if (ccn->irq) {
    err = irq_set_affinity_hint(ccn->irq, &ccn->dt.cpu);
    @@ -1289,12 +1278,13 @@ static int arm_ccn_pmu_init(struct arm_c
    if (err)
    goto error_pmu_register;

    + mutex_lock(&arm_ccn_mutex);
    + list_add(&ccn->dt.entry, &arm_ccn_list);
    + mutex_unlock(&arm_ccn_mutex);
    return 0;

    error_pmu_register:
    error_set_affinity:
    - unregister_cpu_notifier(&ccn->dt.cpu_nb);
    -error_cpu_notifier:
    ida_simple_remove(&arm_ccn_pmu_ida, ccn->dt.id);
    for (i = 0; i < ccn->num_xps; i++)
    writel(0, ccn->xp[i].base + CCN_XP_DT_CONTROL);
    @@ -1306,9 +1296,12 @@ static void arm_ccn_pmu_cleanup(struct a
    {
    int i;

    + mutex_lock(&arm_ccn_mutex);
    + list_del(&ccn->dt.entry);
    + mutex_unlock(&arm_ccn_mutex);
    +
    if (ccn->irq)
    irq_set_affinity_hint(ccn->irq, NULL);
    - unregister_cpu_notifier(&ccn->dt.cpu_nb);
    for (i = 0; i < ccn->num_xps; i++)
    writel(0, ccn->xp[i].base + CCN_XP_DT_CONTROL);
    writel(0, ccn->dt.base + CCN_DT_PMCR);
    @@ -1316,7 +1309,6 @@ static void arm_ccn_pmu_cleanup(struct a
    ida_simple_remove(&arm_ccn_pmu_ida, ccn->dt.id);
    }

    -
    static int arm_ccn_for_each_valid_region(struct arm_ccn *ccn,
    int (*callback)(struct arm_ccn *ccn, int region,
    void __iomem *base, u32 type, u32 id))
    @@ -1533,7 +1525,13 @@ static struct platform_driver arm_ccn_dr

    static int __init arm_ccn_init(void)
    {
    - int i;
    + int i, ret;
    +
    + ret = cpuhp_setup_state_nocalls(CPUHP_AP_PERF_ARM_CCN_ONLINE,
    + "AP_PERF_ARM_CCN_ONLINE", NULL,
    + arm_ccn_pmu_offline_cpu);
    + if (ret)
    + return ret;

    for (i = 0; i < ARRAY_SIZE(arm_ccn_pmu_events); i++)
    arm_ccn_pmu_events_attrs[i] = &arm_ccn_pmu_events[i].attr.attr;
    @@ -1543,6 +1541,7 @@ static int __init arm_ccn_init(void)

    static void __exit arm_ccn_exit(void)
    {
    + cpuhp_remove_state_nocalls(CPUHP_AP_PERF_ARM_CCN_ONLINE);
    platform_driver_unregister(&arm_ccn_driver);
    }

    --- a/include/linux/cpuhotplug.h
    +++ b/include/linux/cpuhotplug.h
    @@ -46,6 +46,7 @@ enum cpuhp_state {
    CPUHP_AP_PERF_S390_CF_ONLINE,
    CPUHP_AP_PERF_S390_SF_ONLINE,
    CPUHP_AP_PERF_ARM_CCI_ONLINE,
    + CPUHP_AP_PERF_ARM_CCN_ONLINE,
    CPUHP_AP_NOTIFY_ONLINE,
    CPUHP_AP_ONLINE_DYN,
    CPUHP_AP_ONLINE_DYN_END = CPUHP_AP_ONLINE_DYN + 30,

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