linux-kernel - Re: [PATCH] ARC: perf: ARC 700 PMU doesn't support sampling events

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Date:	Wed, 13 Nov 2013 16:18:22 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mischa Jonker <Mischa.Jonker@...opsys.com>
Cc:	linux-kernel@...r.kernel.org,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: Re: [PATCH] ARC: perf: ARC 700 PMU doesn't support sampling events

On Wed, Nov 13, 2013 at 04:06:06PM +0100, Mischa Jonker wrote:
> The ARC 700 does not have an interrupt associated with it, and as
> such it cannot trigger when a counter overflows. As the counters are
> 48 bit, it will usually take at least 100 days before a counter
> overflows, so for mere counting of events, there is no problem.
> Sampling is not supported though.

Acked-by: Peter Zijlstra <peterz@...radead.org>

> Cc: Vineet Gupta <vgupta@...opsys.com>
> Signed-off-by: Mischa Jonker <mjonker@...opsys.com>
> ---
>  arch/arc/kernel/perf_event.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arc/kernel/perf_event.c b/arch/arc/kernel/perf_event.c
> index 759e5f3..e46d81f 100644
> --- a/arch/arc/kernel/perf_event.c
> +++ b/arch/arc/kernel/perf_event.c
> @@ -99,6 +99,10 @@ static int arc_pmu_event_init(struct perf_event *event)
>  	struct hw_perf_event *hwc = &event->hw;
>  	int ret;
>  
> +	/* ARC 700 PMU does not support sampling events */
> +	if (is_sampling_event(event))
> +		return -ENOENT;
> +
>  	switch (event->attr.type) {
>  	case PERF_TYPE_HARDWARE:
>  		if (event->attr.config >= PERF_COUNT_HW_MAX)
> -- 
> 1.7.9.5
> 
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