Re: [PATCH v3 3/6] ARCv2: perf: Support sampling events using overflow interrupts

Peter Zijlstra
2015-08-26T13:12:37Z

On Mon, Aug 24, 2015 at 05:20:20PM +0300, Alexey Brodkin wrote:
> @@ -295,6 +317,16 @@ static int arc_pmu_add(struct perf_event *event, int flags)
> }
>
> write_aux_reg(ARC_REG_PCT_INDEX, idx);
> +
> + arc_pmu->act_counter[idx] = event;
> +
> + if (is_sampling_event(event)) {
> + /* Mimic full counter overflow as other arches do */
> + write_aux_reg(ARC_REG_PCT_INT_CNTL, (u32)arc_pmu->max_period);
> + write_aux_reg(ARC_REG_PCT_INT_CNTH,
> + (arc_pmu->max_period >> 32));
> + }
> +

pmu::add should call pmu::start when PERF_EF_START, without that it
should not start the counter, only schedule it.

(although currently all pmu::add() calls will have EF_START set)

> write_aux_reg(ARC_REG_PCT_CONFIG, 0);
> write_aux_reg(ARC_REG_PCT_COUNTL, 0);
> write_aux_reg(ARC_REG_PCT_COUNTH, 0);