[PATCH v2 3/5] arm_pmu: Add support for 64bit event counters

[Suzuki K Poulose]

Each PMU has a set of 32bit event counters. But in some
special cases, the events could be counted using counters
which are effectively 64bit wide.

e.g, Arm V8 PMUv3 has a 64 bit cycle counter which can count
only the CPU cycles. Also, the PMU can chain the event counters
to effectively count as a 64bit counter.

Add support for tracking the events that uses 64bit counters.
This only affects the periods set for each counter in the core
driver.

Cc: Mark Rutland <mark.rutl...@arm.com>
Cc: Will Deacon <will.dea...@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poul...@arm.com>
---
Changes since v1:
 - Rename ARMPMU_EVT_LONG => ARMPMU_EVT_64BIT
---
 drivers/perf/arm_pmu.c       | 14 ++++++++------
 include/linux/perf/arm_pmu.h |  6 ++++++
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index 8962d26..ff858e6 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -28,9 +28,10 @@
 static DEFINE_PER_CPU(struct arm_pmu *, cpu_armpmu);
 static DEFINE_PER_CPU(int, cpu_irq);
 
-static inline u64 arm_pmu_max_period(void)
+static inline u64 arm_pmu_event_max_period(struct perf_event *event)
 {
-       return (1ULL << 32) - 1;
+       return (event->hw.flags & ARMPMU_EVT_64BIT) ?
+               ~0ULL : (1ULL << 32) - 1;
 }
 
 static int
@@ -122,7 +123,7 @@ int armpmu_event_set_period(struct perf_event *event)
        u64 max_period;
        int ret = 0;
 
-       max_period = arm_pmu_max_period();
+       max_period = arm_pmu_event_max_period(event);
        if (unlikely(left <= -period)) {
                left = period;
                local64_set(&hwc->period_left, left);
@@ -148,7 +149,7 @@ int armpmu_event_set_period(struct perf_event *event)
 
        local64_set(&hwc->prev_count, (u64)-left);
 
-       armpmu->write_counter(event, (u64)(-left) & 0xffffffff);
+       armpmu->write_counter(event, (u64)(-left) & max_period);
 
        perf_event_update_userpage(event);
 
@@ -160,7 +161,7 @@ u64 armpmu_event_update(struct perf_event *event)
        struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
        struct hw_perf_event *hwc = &event->hw;
        u64 delta, prev_raw_count, new_raw_count;
-       u64 max_period = arm_pmu_max_period();
+       u64 max_period = arm_pmu_event_max_period(event);
 
 again:
        prev_raw_count = local64_read(&hwc->prev_count);
@@ -368,6 +369,7 @@ __hw_perf_event_init(struct perf_event *event)
        struct hw_perf_event *hwc = &event->hw;
        int mapping;
 
+       hwc->flags = 0;
        mapping = armpmu->map_event(event);
 
        if (mapping < 0) {
@@ -410,7 +412,7 @@ __hw_perf_event_init(struct perf_event *event)
                 * is far less likely to overtake the previous one unless
                 * you have some serious IRQ latency issues.
                 */
-               hwc->sample_period  = arm_pmu_max_period() >> 1;
+               hwc->sample_period  = arm_pmu_event_max_period(event) >> 1;
                hwc->last_period    = hwc->sample_period;
                local64_set(&hwc->period_left, hwc->sample_period);
        }
diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
index f1cfe12..1e26b14 100644
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h
@@ -25,6 +25,12 @@
  */
 #define ARMPMU_MAX_HWEVENTS            32
 
+/*
+ * ARM PMU hw_event flags
+ */
+/* Event uses a 64bit counter */
+#define ARMPMU_EVT_64BIT               1
+
 #define HW_OP_UNSUPPORTED              0xFFFF
 #define C(_x)                          PERF_COUNT_HW_CACHE_##_x
 #define CACHE_OP_UNSUPPORTED           0xFFFF
-- 
2.7.4