Perf: Add API to check for PMU constraints
Extend ARM perf to check if PMU's have any special
constraints for adding events.
e.g. MSM PMU's have column exclusion constraints
that restrict adding events from the same register
and same group.
Change-Id: I36ea093c523f90f083d66dc6995e66cd77129bbd
Signed-off-by: Ashwin Chaugule <ashwinc@codeaurora.org>
diff --git a/arch/arm/include/asm/pmu.h b/arch/arm/include/asm/pmu.h
index e6809ca..37cbfcb 100644
--- a/arch/arm/include/asm/pmu.h
+++ b/arch/arm/include/asm/pmu.h
@@ -129,6 +129,8 @@
u64 max_period;
struct platform_device *plat_device;
struct pmu_hw_events *(*get_hw_events)(void);
+ int (*test_set_event_constraints)(struct perf_event *event);
+ int (*clear_event_constraints)(struct perf_event *event);
};
#define to_arm_pmu(p) (container_of(p, struct arm_pmu, pmu))
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 7fdac82..e37b28b 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -273,6 +273,10 @@
hw_events->events[idx] = NULL;
clear_bit(idx, hw_events->used_mask);
+ /* Clear event constraints. */
+ if (armpmu->clear_event_constraints)
+ armpmu->clear_event_constraints(event);
+
perf_event_update_userpage(event);
}
@@ -286,6 +290,17 @@
int err = 0;
perf_pmu_disable(event->pmu);
+ /*
+ * Tests if event is constrained. If not sets it so that next
+ * collision can be detected.
+ */
+ if (armpmu->test_set_event_constraints)
+ if (armpmu->test_set_event_constraints(event) < 0) {
+ pr_err("Event: %llx failed constraint check.\n",
+ event->attr.config);
+ event->state = PERF_EVENT_STATE_OFF;
+ goto out;
+ }
/* If we don't have a space for the counter then finish early. */
idx = armpmu->get_event_idx(hw_events, hwc);
@@ -517,6 +532,7 @@
return -EPERM;
}
+
/*
* Store the event encoding into the config_base field.
*/
diff --git a/arch/arm/kernel/perf_event_msm_krait.c b/arch/arm/kernel/perf_event_msm_krait.c
index 8dbd047..1b115b4 100644
--- a/arch/arm/kernel/perf_event_msm_krait.c
+++ b/arch/arm/kernel/perf_event_msm_krait.c
@@ -58,6 +58,17 @@
static u32 krait_ver, evt_index;
static u32 krait_max_l1_reg;
+
+/*
+ * Every 4 bytes represents a prefix.
+ * Every nibble represents a register.
+ * Every bit represents a group within a register.
+ *
+ * This supports up to 4 groups per register, upto 8
+ * registers per prefix and upto 2 prefixes.
+ */
+static DEFINE_PER_CPU(u64, pmu_bitmap);
+
static const unsigned armv7_krait_perf_map[PERF_COUNT_HW_MAX] = {
[PERF_COUNT_HW_CPU_CYCLES] = ARMV7_PERFCTR_CPU_CYCLES,
[PERF_COUNT_HW_INSTRUCTIONS] = ARMV7_PERFCTR_INSTR_EXECUTED,
@@ -556,6 +567,58 @@
}
}
+/*
+ * We check for column exclusion constraints here.
+ * Two events cant have same reg and same group.
+ */
+static int msm_test_set_ev_constraint(struct perf_event *event)
+{
+ u32 krait_evt_type = event->attr.config & KRAIT_EVENT_MASK;
+ u8 prefix = (krait_evt_type & 0xF0000) >> 16;
+ u8 reg = (krait_evt_type & 0x0F000) >> 12;
+ u8 group = krait_evt_type & 0x0000F;
+ u64 cpu_pmu_bitmap = __get_cpu_var(pmu_bitmap);
+ u64 bitmap_t;
+
+ /* Return if non MSM event. */
+ if (!prefix)
+ return 0;
+
+ bitmap_t = 1 << (((prefix - 1) * 32) + (reg * 4) + group);
+
+ /* Set it if not already set. */
+ if (!(cpu_pmu_bitmap & bitmap_t)) {
+ cpu_pmu_bitmap |= bitmap_t;
+ __get_cpu_var(pmu_bitmap) = cpu_pmu_bitmap;
+ return 1;
+ }
+ /* Bit is already set. Constraint failed. */
+ return -EPERM;
+}
+
+static int msm_clear_ev_constraint(struct perf_event *event)
+{
+ u32 krait_evt_type = event->attr.config & KRAIT_EVENT_MASK;
+ u8 prefix = (krait_evt_type & 0xF0000) >> 16;
+ u8 reg = (krait_evt_type & 0x0F000) >> 12;
+ u8 group = krait_evt_type & 0x0000F;
+ u64 cpu_pmu_bitmap = __get_cpu_var(pmu_bitmap);
+ u64 bitmap_t;
+
+ /* Return if non MSM event. */
+ if (!prefix)
+ return 0;
+
+ bitmap_t = 1 << (((prefix - 1) * 32) + (reg * 4) + group);
+
+ /* Clear constraint bit. */
+ cpu_pmu_bitmap &= ~(bitmap_t);
+
+ __get_cpu_var(pmu_bitmap) = cpu_pmu_bitmap;
+
+ return 1;
+}
+
static struct arm_pmu krait_pmu = {
.handle_irq = armv7pmu_handle_irq,
.request_pmu_irq = msm_request_irq,
@@ -568,6 +631,8 @@
.start = armv7pmu_start,
.stop = armv7pmu_stop,
.reset = krait_pmu_reset,
+ .test_set_event_constraints = msm_test_set_ev_constraint,
+ .clear_event_constraints = msm_clear_ev_constraint,
.max_period = (1LLU << 32) - 1,
};