1 files changed, 22 insertions, 4 deletions

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 4520c9356b54..6b0641c3f03f 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -485,7 +485,7 @@ static bool is_ebb_event(struct perf_event *event)
 	 * check that the PMU supports EBB, meaning those that don't can still
 	 * use bit 63 of the event code for something else if they wish.
 	 */
-	return (ppmu->flags & PPMU_EBB) &&
+	return (ppmu->flags & PPMU_ARCH_207S) &&
 	       ((event->attr.config >> PERF_EVENT_CONFIG_EBB_SHIFT) & 1);
 }
 
@@ -777,7 +777,7 @@ void perf_event_print_debug(void)
 	if (ppmu->flags & PPMU_HAS_SIER)
 		sier = mfspr(SPRN_SIER);
 
-	if (ppmu->flags & PPMU_EBB) {
+	if (ppmu->flags & PPMU_ARCH_207S) {
 		pr_info("MMCR2: %016lx EBBHR: %016lx\n",
 			mfspr(SPRN_MMCR2), mfspr(SPRN_EBBHR));
 		pr_info("EBBRR: %016lx BESCR: %016lx\n",
@@ -996,7 +996,22 @@ static void power_pmu_read(struct perf_event *event)
 	} while (local64_cmpxchg(&event->hw.prev_count, prev, val) != prev);
 
 	local64_add(delta, &event->count);
-	local64_sub(delta, &event->hw.period_left);
+
+	/*
+	 * A number of places program the PMC with (0x80000000 - period_left).
+	 * We never want period_left to be less than 1 because we will program
+	 * the PMC with a value >= 0x800000000 and an edge detected PMC will
+	 * roll around to 0 before taking an exception. We have seen this
+	 * on POWER8.
+	 *
+	 * To fix this, clamp the minimum value of period_left to 1.
+	 */
+	do {
+		prev = local64_read(&event->hw.period_left);
+		val = prev - delta;
+		if (val < 1)
+			val = 1;
+	} while (local64_cmpxchg(&event->hw.period_left, prev, val) != prev);
 }
 
 /*
@@ -1300,6 +1315,9 @@ static void power_pmu_enable(struct pmu *pmu)
 
 	write_mmcr0(cpuhw, mmcr0);
 
+	if (ppmu->flags & PPMU_ARCH_207S)
+		mtspr(SPRN_MMCR2, 0);
+
 	/*
 	 * Enable instruction sampling if necessary
 	 */
@@ -1696,7 +1714,7 @@ static int power_pmu_event_init(struct perf_event *event)
 
 	if (has_branch_stack(event)) {
 	        /* PMU has BHRB enabled */
-		if (!(ppmu->flags & PPMU_BHRB))
+		if (!(ppmu->flags & PPMU_ARCH_207S))
 			return -EOPNOTSUPP;
 	}