diff options
| -rw-r--r-- | Documentation/arm/CCN.txt | 15 | ||||
| -rw-r--r-- | drivers/bus/arm-ccn.c | 128 |
2 files changed, 126 insertions, 17 deletions
diff --git a/Documentation/arm/CCN.txt b/Documentation/arm/CCN.txt index 0632b3a..3a76048 100644 --- a/Documentation/arm/CCN.txt +++ b/Documentation/arm/CCN.txt @@ -33,6 +33,13 @@ directory, with first 8 configurable by user and additional Cycle counter is described by a "type" value 0xff and does not require any other settings. +The driver also provides a "cpumask" sysfs attribute, which contains +a single CPU ID, of the processor which will be used to handle all +the CCN PMU events. It is recommended that the user space tools +request the events on this processor (if not, the perf_event->cpu value +will be overwritten anyway). In case of this processor being offlined, +the events are migrated to another one and the attribute is updated. + Example of perf tool use: / # perf list | grep ccn @@ -41,12 +48,8 @@ Example of perf tool use: ccn/xp_valid_flit/ [Kernel PMU event] <...> -/ # perf stat -C 0 -e ccn/cycles/,ccn/xp_valid_flit,xp=1,port=0,vc=1,dir=1/ \ +/ # perf stat -a -e ccn/cycles/,ccn/xp_valid_flit,xp=1,port=0,vc=1,dir=1/ \ sleep 1 The driver does not support sampling, therefore "perf record" will -not work. Also notice that only single cpu is being selected -("-C 0") - this is because perf framework does not support -"non-CPU related" counters (yet?) so system-wide session ("-a") -would try (and in most cases fail) to set up the same event -per each CPU. +not work. Per-task (without "-a") perf sessions are not supported. diff --git a/drivers/bus/arm-ccn.c b/drivers/bus/arm-ccn.c index 60397ec..3374dcb 100644 --- a/drivers/bus/arm-ccn.c +++ b/drivers/bus/arm-ccn.c @@ -166,13 +166,17 @@ struct arm_ccn_dt { struct hrtimer hrtimer; + cpumask_t cpu; + struct notifier_block cpu_nb; + struct pmu pmu; }; struct arm_ccn { struct device *dev; void __iomem *base; - unsigned irq_used:1; + unsigned int irq; + unsigned sbas_present:1; unsigned sbsx_present:1; @@ -521,6 +525,25 @@ static struct attribute_group arm_ccn_pmu_cmp_mask_attr_group = { .attrs = arm_ccn_pmu_cmp_mask_attrs, }; +static ssize_t arm_ccn_pmu_cpumask_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct arm_ccn *ccn = pmu_to_arm_ccn(dev_get_drvdata(dev)); + + return cpumap_print_to_pagebuf(true, buf, &ccn->dt.cpu); +} + +static struct device_attribute arm_ccn_pmu_cpumask_attr = + __ATTR(cpumask, S_IRUGO, arm_ccn_pmu_cpumask_show, NULL); + +static struct attribute *arm_ccn_pmu_cpumask_attrs[] = { + &arm_ccn_pmu_cpumask_attr.attr, + NULL, +}; + +static struct attribute_group arm_ccn_pmu_cpumask_attr_group = { + .attrs = arm_ccn_pmu_cpumask_attrs, +}; /* * Default poll period is 10ms, which is way over the top anyway, @@ -542,6 +565,7 @@ static const struct attribute_group *arm_ccn_pmu_attr_groups[] = { &arm_ccn_pmu_events_attr_group, &arm_ccn_pmu_format_attr_group, &arm_ccn_pmu_cmp_mask_attr_group, + &arm_ccn_pmu_cpumask_attr_group, NULL }; @@ -642,6 +666,16 @@ static int arm_ccn_pmu_event_init(struct perf_event *event) dev_warn(ccn->dev, "Can't provide per-task data!\n"); return -EOPNOTSUPP; } + /* + * Many perf core operations (eg. events rotation) operate on a + * single CPU context. This is obvious for CPU PMUs, where one + * expects the same sets of events being observed on all CPUs, + * but can lead to issues for off-core PMUs, like CCN, where each + * event could be theoretically assigned to a different CPU. To + * mitigate this, we enforce CPU assignment to one, selected + * processor (the one described in the "cpumask" attribute). + */ + event->cpu = cpumask_first(&ccn->dt.cpu); node_xp = CCN_CONFIG_NODE(event->attr.config); type = CCN_CONFIG_TYPE(event->attr.config); @@ -835,9 +869,15 @@ static void arm_ccn_pmu_event_start(struct perf_event *event, int flags) arm_ccn_pmu_read_counter(ccn, hw->idx)); hw->state = 0; - if (!ccn->irq_used) - hrtimer_start(&ccn->dt.hrtimer, arm_ccn_pmu_timer_period(), - HRTIMER_MODE_REL); + /* + * Pin the timer, so that the overflows are handled by the chosen + * event->cpu (this is the same one as presented in "cpumask" + * attribute). + */ + if (!ccn->irq) + __hrtimer_start_range_ns(&ccn->dt.hrtimer, + arm_ccn_pmu_timer_period(), 0, + HRTIMER_MODE_REL_PINNED, 0); /* Set the DT bus input, engaging the counter */ arm_ccn_pmu_xp_dt_config(event, 1); @@ -852,7 +892,7 @@ static void arm_ccn_pmu_event_stop(struct perf_event *event, int flags) /* Disable counting, setting the DT bus to pass-through mode */ arm_ccn_pmu_xp_dt_config(event, 0); - if (!ccn->irq_used) + if (!ccn->irq) hrtimer_cancel(&ccn->dt.hrtimer); /* Let the DT bus drain */ @@ -1079,12 +1119,39 @@ static enum hrtimer_restart arm_ccn_pmu_timer_handler(struct hrtimer *hrtimer) } +static int arm_ccn_pmu_cpu_notifier(struct notifier_block *nb, + unsigned long action, void *hcpu) +{ + 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 */ + unsigned int target; + + switch (action & ~CPU_TASKS_FROZEN) { + case CPU_DOWN_PREPARE: + if (!cpumask_test_and_clear_cpu(cpu, &dt->cpu)) + break; + target = cpumask_any_but(cpu_online_mask, cpu); + if (target < 0) + break; + perf_pmu_migrate_context(&dt->pmu, cpu, target); + cpumask_set_cpu(target, &dt->cpu); + WARN_ON(irq_set_affinity(ccn->irq, &dt->cpu) != 0); + default: + break; + } + + return NOTIFY_OK; +} + + static DEFINE_IDA(arm_ccn_pmu_ida); static int arm_ccn_pmu_init(struct arm_ccn *ccn) { int i; char *name; + int err; /* Initialize DT subsystem */ ccn->dt.base = ccn->base + CCN_REGION_SIZE; @@ -1136,20 +1203,58 @@ static int arm_ccn_pmu_init(struct arm_ccn *ccn) }; /* No overflow interrupt? Have to use a timer instead. */ - if (!ccn->irq_used) { + if (!ccn->irq) { dev_info(ccn->dev, "No access to interrupts, using timer.\n"); hrtimer_init(&ccn->dt.hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); ccn->dt.hrtimer.function = arm_ccn_pmu_timer_handler; } - return perf_pmu_register(&ccn->dt.pmu, name, -1); + /* 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(ccn->irq, &ccn->dt.cpu); + if (err) { + dev_err(ccn->dev, "Failed to set interrupt affinity!\n"); + goto error_set_affinity; + } + } + + err = perf_pmu_register(&ccn->dt.pmu, name, -1); + if (err) + goto error_pmu_register; + + 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); + writel(0, ccn->dt.base + CCN_DT_PMCR); + return err; } static void arm_ccn_pmu_cleanup(struct arm_ccn *ccn) { int i; + irq_set_affinity(ccn->irq, cpu_possible_mask); + 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); @@ -1285,6 +1390,7 @@ static int arm_ccn_probe(struct platform_device *pdev) { struct arm_ccn *ccn; struct resource *res; + unsigned int irq; int err; ccn = devm_kzalloc(&pdev->dev, sizeof(*ccn), GFP_KERNEL); @@ -1309,6 +1415,7 @@ static int arm_ccn_probe(struct platform_device *pdev) res = platform_get_resource(pdev, IORESOURCE_IRQ, 0); if (!res) return -EINVAL; + irq = res->start; /* Check if we can use the interrupt */ writel(CCN_MN_ERRINT_STATUS__PMU_EVENTS__DISABLE, @@ -1318,13 +1425,12 @@ static int arm_ccn_probe(struct platform_device *pdev) /* Can set 'disable' bits, so can acknowledge interrupts */ writel(CCN_MN_ERRINT_STATUS__PMU_EVENTS__ENABLE, ccn->base + CCN_MN_ERRINT_STATUS); - err = devm_request_irq(ccn->dev, res->start, - arm_ccn_irq_handler, 0, dev_name(ccn->dev), - ccn); + err = devm_request_irq(ccn->dev, irq, arm_ccn_irq_handler, 0, + dev_name(ccn->dev), ccn); if (err) return err; - ccn->irq_used = 1; + ccn->irq = irq; } |
