The csky pmu counter may have different io width. When the counter is
smaller then 64 bits and counter value is smaller than the old value, it
will result to a extremely large delta value. So the sampled value should
be extend to 64 bits to avoid this, the extension bits base on the
count-width property from dts.
Signed-off-by: Mao Han <han_mao@xxxxxxxxx>
Cc: Guo Ren <guoren@xxxxxxxxxx>
---
arch/csky/kernel/perf_event.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/arch/csky/kernel/perf_event.c b/arch/csky/kernel/perf_event.c
index c022acc..36f7f20 100644
--- a/arch/csky/kernel/perf_event.c
+++ b/arch/csky/kernel/perf_event.c
@@ -9,6 +9,7 @@
#include <linux/platform_device.h>
#define CSKY_PMU_MAX_EVENTS 32
+#define DEFAULT_COUNT_WIDTH 48
#define HPCR "<0, 0x0>" /* PMU Control reg */
#define HPCNTENR "<0, 0x4>" /* Count Enable reg */
@@ -18,6 +19,7 @@ static void (*hw_raw_write_mapping[CSKY_PMU_MAX_EVENTS])(uint64_t val);
struct csky_pmu_t {
struct pmu pmu;
+ uint32_t count_width;
uint32_t hpcr;
} csky_pmu;
@@ -806,7 +808,12 @@ static void csky_perf_event_update(struct perf_event *event,
struct hw_perf_event *hwc)
{
uint64_t prev_raw_count = local64_read(&hwc->prev_count);
- uint64_t new_raw_count = hw_raw_read_mapping[hwc->idx]();
+ /*
+ * Sign extend count value to 64bit, otherwise delta calculation
+ * would be incorrect when overflow occurs.
+ */
+ uint64_t new_raw_count = sign_extend64(
+ hw_raw_read_mapping[hwc->idx](), csky_pmu.count_width);
int64_t delta = new_raw_count - prev_raw_count;
/*
@@ -1045,6 +1052,11 @@ int csky_pmu_device_probe(struct platform_device *pdev,
ret = init_fn(&csky_pmu);
}
+ if (!of_property_read_u32(node, "count-width",
+ &csky_pmu.count_width)) {
+ csky_pmu.count_width = DEFAULT_COUNT_WIDTH;
+ }
+
if (ret) {
pr_notice("[perf] failed to probe PMU!\n");
return ret;
--
2.7.4
