Date: Wed, 26 Aug 2015 15:12:25 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
        Vineet.Gupta1@synopsys.com, arc-linux-dev@synopsys.com, arnd@arndb.de,
        Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: [PATCH v3 3/6] ARCv2: perf: Support sampling events using
 overflow interrupts
Message-ID: <20150826131225.GD19282@twins.programming.kicks-ass.net>
References: <1440426023-2792-1-git-send-email-abrodkin@synopsys.com>
 <1440426023-2792-4-git-send-email-abrodkin@synopsys.com>
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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);


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