Merge branch 'for-linus' of git://git.linaro.org/people/rmk/linux-arm

[linux-flexiantxendom0-3.2.10.git] / arch / arm / kernel / perf_event.c

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index ab59c3b..186c8cb 100644 (file)
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -180,7 +180,7 @@ armpmu_event_set_period(struct perf_event *event,
 u64
 armpmu_event_update(struct perf_event *event,
                    struct hw_perf_event *hwc,
-                   int idx, int overflow)
+                   int idx)
 {
        struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
        u64 delta, prev_raw_count, new_raw_count;
@@ -193,13 +193,7 @@ again:
                             new_raw_count) != prev_raw_count)
                goto again;
 
-       new_raw_count &= armpmu->max_period;
-       prev_raw_count &= armpmu->max_period;
-
-       if (overflow)
-               delta = armpmu->max_period - prev_raw_count + new_raw_count + 1;
-       else
-               delta = new_raw_count - prev_raw_count;
+       delta = (new_raw_count - prev_raw_count) & armpmu->max_period;
 
        local64_add(delta, &event->count);
        local64_sub(delta, &hwc->period_left);
@@ -216,7 +210,7 @@ armpmu_read(struct perf_event *event)
        if (hwc->idx < 0)
                return;
 
-       armpmu_event_update(event, hwc, hwc->idx, 0);
+       armpmu_event_update(event, hwc, hwc->idx);
 }
 
 static void
@@ -232,7 +226,7 @@ armpmu_stop(struct perf_event *event, int flags)
        if (!(hwc->state & PERF_HES_STOPPED)) {
                armpmu->disable(hwc, hwc->idx);
                barrier(); /* why? */
-               armpmu_event_update(event, hwc, hwc->idx, 0);
+               armpmu_event_update(event, hwc, hwc->idx);
                hwc->state |= PERF_HES_STOPPED | PERF_HES_UPTODATE;
        }
 }
@@ -518,7 +512,13 @@ __hw_perf_event_init(struct perf_event *event)
        hwc->config_base            |= (unsigned long)mapping;
 
        if (!hwc->sample_period) {
-               hwc->sample_period  = armpmu->max_period;
+               /*
+                * For non-sampling runs, limit the sample_period to half
+                * of the counter width. That way, the new counter value
+                * is far less likely to overtake the previous one unless
+                * you have some serious IRQ latency issues.
+                */
+               hwc->sample_period  = armpmu->max_period >> 1;
                hwc->last_period    = hwc->sample_period;
                local64_set(&hwc->period_left, hwc->sample_period);
        }
@@ -539,6 +539,10 @@ static int armpmu_event_init(struct perf_event *event)
        int err = 0;
        atomic_t *active_events = &armpmu->active_events;
 
+       /* does not support taken branch sampling */
+       if (has_branch_stack(event))
+               return -EOPNOTSUPP;
+
        if (armpmu->map_event(event) == -ENOENT)
                return -ENOENT;
 
@@ -680,6 +684,28 @@ static void __init cpu_pmu_init(struct arm_pmu *armpmu)
 }
 
 /*
+ * PMU hardware loses all context when a CPU goes offline.
+ * When a CPU is hotplugged back in, since some hardware registers are
+ * UNKNOWN at reset, the PMU must be explicitly reset to avoid reading
+ * junk values out of them.
+ */
+static int __cpuinit pmu_cpu_notify(struct notifier_block *b,
+                                       unsigned long action, void *hcpu)
+{
+       if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING)
+               return NOTIFY_DONE;
+
+       if (cpu_pmu && cpu_pmu->reset)
+               cpu_pmu->reset(NULL);
+
+       return NOTIFY_OK;
+}
+
+static struct notifier_block __cpuinitdata pmu_cpu_notifier = {
+       .notifier_call = pmu_cpu_notify,
+};
+
+/*
  * CPU PMU identification and registration.
  */
 static int __init
@@ -733,6 +759,7 @@ init_hw_perf_events(void)
                pr_info("enabled with %s PMU driver, %d counters available\n",
                        cpu_pmu->name, cpu_pmu->num_events);
                cpu_pmu_init(cpu_pmu);
+               register_cpu_notifier(&pmu_cpu_notifier);
                armpmu_register(cpu_pmu, "cpu", PERF_TYPE_RAW);
        } else {
                pr_info("no hardware support available\n");