linux-kernel - Re: [PATCH 6/7] drivers/perf: hisi_pcie: Merge find_related_event() and get_event

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Date: Thu, 8 Feb 2024 12:39:46 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Yicong Yang <yangyicong@...wei.com>
CC: <will@...nel.org>, <mark.rutland@....com>, <hejunhao3@...wei.com>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
	<yangyicong@...ilicon.com>, <linuxarm@...wei.com>,
	<prime.zeng@...ilicon.com>, <fanghao11@...wei.com>
Subject: Re: [PATCH 6/7] drivers/perf: hisi_pcie: Merge find_related_event()
 and get_event_idx()

On Sun, 4 Feb 2024 15:45:26 +0800
Yicong Yang <yangyicong@...wei.com> wrote:

> From: Junhao He <hejunhao3@...wei.com>
> 
> The function xxx_find_related_event() scan all working events to find
> related events. During this process, we also can find the idle counters.
> If not found related events, return the first idle counter to simplify
> the code.
> 
> Signed-off-by: Junhao He <hejunhao3@...wei.com>
> Signed-off-by: Yicong Yang <yangyicong@...ilicon.com>

A suggestion inline to avoid the magic HISI_PCIE_MAX_COUNTER value
being used outside of the function. 

> ---
>  drivers/perf/hisilicon/hisi_pcie_pmu.c | 55 ++++++++++----------------
>  1 file changed, 21 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/perf/hisilicon/hisi_pcie_pmu.c b/drivers/perf/hisilicon/hisi_pcie_pmu.c
> index 1b45aeb82859..2edde66675e7 100644
> --- a/drivers/perf/hisilicon/hisi_pcie_pmu.c
> +++ b/drivers/perf/hisilicon/hisi_pcie_pmu.c
> @@ -397,16 +397,24 @@ static u64 hisi_pcie_pmu_read_counter(struct perf_event *event)
>  	return hisi_pcie_pmu_readq(pcie_pmu, event->hw.event_base, idx);
>  }
>  
> -static int hisi_pcie_pmu_find_related_event(struct hisi_pcie_pmu *pcie_pmu,
> -					    struct perf_event *event)
> +/*
> + * Check all work events, if a relevant event is found then we return it
> + * first, otherwise return the first idle counter (need to reset).
> + */
> +static int hisi_pcie_pmu_get_event_idx(struct hisi_pcie_pmu *pcie_pmu,
> +					struct perf_event *event)
>  {
> +	int first_idle = HISI_PCIE_MAX_COUNTERS;
	int first_idle = -EAGAIN;
>  	struct perf_event *sibling;
>  	int idx;
>  
>  	for (idx = 0; idx < HISI_PCIE_MAX_COUNTERS; idx++) {
>  		sibling = pcie_pmu->hw_events[idx];
> -		if (!sibling)
> +		if (!sibling) {
> +			if (first_idle == HISI_PCIE_MAX_COUNTERS)
if (first_idle == -EAGAIN)

> +				first_idle = idx;
>  			continue;
> +		}
>  
>  		/* Related events must be used in group */
>  		if (hisi_pcie_pmu_cmp_event(sibling, event) &&
> @@ -414,19 +422,7 @@ static int hisi_pcie_pmu_find_related_event(struct hisi_pcie_pmu *pcie_pmu,
>  			return idx;
>  	}
>  
> -	return idx;
> -}
> -
> -static int hisi_pcie_pmu_get_event_idx(struct hisi_pcie_pmu *pcie_pmu)
> -{
> -	int idx;
> -
> -	for (idx = 0; idx < HISI_PCIE_MAX_COUNTERS; idx++) {
> -		if (!pcie_pmu->hw_events[idx])
> -			return idx;
> -	}
> -
> -	return -EINVAL;
> +	return first_idle;
Then this will return -EAGAIN;
>  }
>  
>  static void hisi_pcie_pmu_event_update(struct perf_event *event)
> @@ -552,27 +548,18 @@ static int hisi_pcie_pmu_add(struct perf_event *event, int flags)
>  
>  	hwc->state = PERF_HES_STOPPED | PERF_HES_UPTODATE;
>  
> -	/* Check all working events to find a related event. */
> -	idx = hisi_pcie_pmu_find_related_event(pcie_pmu, event);
> -	if (idx < 0)
> -		return idx;
> -
> -	/* Current event shares an enabled counter with the related event */
> -	if (idx < HISI_PCIE_MAX_COUNTERS) {
> -		hwc->idx = idx;
> -		goto start_count;
> -	}
> -
> -	idx = hisi_pcie_pmu_get_event_idx(pcie_pmu);
> -	if (idx < 0)
> -		return idx;
> +	idx = hisi_pcie_pmu_get_event_idx(pcie_pmu, event);
> +	if (idx == HISI_PCIE_MAX_COUNTERS)
> +		return -EAGAIN;

Perhaps simpler to handle first_idle == HISI_PCIE_MAX_COUNTERS as
an error return in hisi_pcie_pmu_get_event_idx - see above.

 	if (idx < 0)
		return idx;


>  
>  	hwc->idx = idx;
> -	pcie_pmu->hw_events[idx] = event;
> -	/* Reset Counter to avoid previous statistic interference. */
> -	hisi_pcie_pmu_reset_counter(pcie_pmu, idx);
>  
> -start_count:
> +	/* No enabled counter found with related event, reset it */
> +	if (!pcie_pmu->hw_events[idx]) {
> +		hisi_pcie_pmu_reset_counter(pcie_pmu, idx);
> +		pcie_pmu->hw_events[idx] = event;
> +	}
> +
>  	if (flags & PERF_EF_START)
>  		hisi_pcie_pmu_start(event, PERF_EF_RELOAD);
>