Hi Mao,
On Tue, Jun 4, 2019 at 10:25 AM Mao Han <han_mao@xxxxxxxxx> wrote:
>
> 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);
csky_pmu.count_width - 1 ? we need index here.
Best Regards
Guo Ren
