ARM: perf: add hook for event index clearing

On Krait processors we have a many-to-one relationship between
raw CPU events and the event programmed into the PMNx counter.
Two raw CPU events could map to the same value programmed in the
PMNx counter. To avoid this problem, we check for collisions
during the get_event_idx() callback by setting a bit in a bitmap
whenever a certain event is used in a PMNx counter (see the next
patch). Unfortunately, we don't have a hook to clear this bit in
the bitmap when the event is deleted so let's add an optional
clear_event_idx() callback for this purpose.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm/include/asm/pmu.h b/arch/arm/include/asm/pmu.h
index f24edad26c70fd34fb9182179ae87618bbb72da8..ae1919be8f988a68d109963f087912128d773dbc 100644 (file)
--- a/arch/arm/include/asm/pmu.h
+++ b/arch/arm/include/asm/pmu.h
@@ -71,6 +71,8 @@ struct arm_pmu {
        void            (*disable)(struct perf_event *event);
        int             (*get_event_idx)(struct pmu_hw_events *hw_events,
                                         struct perf_event *event);
+       void            (*clear_event_idx)(struct pmu_hw_events *hw_events,
+                                        struct perf_event *event);
        int             (*set_event_filter)(struct hw_perf_event *evt,
                                            struct perf_event_attr *attr);
        u32             (*read_counter)(struct perf_event *event);

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index b0c8489018d3d64764bbe630ce6d0ee983b378b8..361a1aaee7c8df33ce26fe8057c8f00e4c893078 100644 (file)
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -207,6 +207,8 @@ armpmu_del(struct perf_event *event, int flags)
        armpmu_stop(event, PERF_EF_UPDATE);
        hw_events->events[idx] = NULL;
        clear_bit(idx, hw_events->used_mask);
+       if (armpmu->clear_event_idx)
+               armpmu->clear_event_idx(hw_events, event);
 
        perf_event_update_userpage(event);
 }