linux-kernel - Re: [PATCH v7 2/4] perf/smmuv3: Add arm64 smmuv3 pmu driver

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Message-ID: <fa89c332-d420-8fef-5034-518e60571bd9@arm.com>
Date:   Tue, 26 Mar 2019 16:57:42 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
        lorenzo.pieralisi@....com
Cc:     andrew.murray@....com, jean-philippe.brucker@....com,
        will.deacon@....com, mark.rutland@....com, guohanjun@...wei.com,
        john.garry@...wei.com, pabba@...eaurora.org,
        vkilari@...eaurora.org, rruigrok@...eaurora.org,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linuxarm@...wei.com,
        neil.m.leeder@...il.com
Subject: Re: [PATCH v7 2/4] perf/smmuv3: Add arm64 smmuv3 pmu driver

Hi Shameer,

On 26/03/2019 15:17, Shameer Kolothum wrote:
[...]
> +static int smmu_pmu_apply_event_filter(struct smmu_pmu *smmu_pmu,
> +				       struct perf_event *event, int idx)
> +{
> +	u32 span, sid;
> +	unsigned int num_ctrs = smmu_pmu->num_counters;
> +	bool filter_en = !!get_filter_enable(event);
> +
> +	span = filter_en ? get_filter_span(event) :
> +			   SMMU_PMCG_DEFAULT_FILTER_SPAN;
> +	sid = filter_en ? get_filter_stream_id(event) :
> +			   SMMU_PMCG_DEFAULT_FILTER_SID;
> +
> +	/* Support individual filter settings */
> +	if (!smmu_pmu->global_filter) {
> +		smmu_pmu_set_event_filter(event, idx, span, sid);
> +		return 0;
> +	}
> +
> +	/* Requested settings same as current global settings*/
> +	if (span == smmu_pmu->global_filter_span &&
> +	    sid == smmu_pmu->global_filter_sid)
> +		return 0;
> +
> +	if (!bitmap_empty(smmu_pmu->used_counters, num_ctrs))
> +		return -EAGAIN;
> +
> +	if (idx == 0) {
> +		smmu_pmu_set_event_filter(event, idx, span, sid);
> +		smmu_pmu->global_filter_span = span;
> +		smmu_pmu->global_filter_sid = sid;
> +		return 0;
> +	}

When I suggested dropping the check of idx, I did mean removing it 
entirely, not just moving it further down ;)

Nothing to worry about though, I'll just leave this here for Will to 
consider applying on top or squashing.

Thanks,
Robin.

----->8-----
From: Robin Murphy <robin.murphy@....com>
Subject: [PATCH] perf/smmuv3: Relax global filter constraint a little

Although the current behaviour of smmu_pmu_get_event_idx() effectively
ensures that the first-allocated counter will be counter 0, there's no
need to strictly enforce that in smmu_pmu_apply_event_filter(). All that
matters is that we only ever touch the global filter settings in
SMMU_PMCG_SMR0 and SMMU_PMCG_EVTYPER0 while no counters are active.

Signed-off-by: Robin Murphy <robin.murphy@....com>
---
  drivers/perf/arm_smmuv3_pmu.c | 11 ++++-------
  1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
index 6b3c0ed7ad71..23045ead6de1 100644
--- a/drivers/perf/arm_smmuv3_pmu.c
+++ b/drivers/perf/arm_smmuv3_pmu.c
@@ -286,14 +286,11 @@ static int smmu_pmu_apply_event_filter(struct 
smmu_pmu *smmu_pmu,
  	if (!bitmap_empty(smmu_pmu->used_counters, num_ctrs))
  		return -EAGAIN;

-	if (idx == 0) {
-		smmu_pmu_set_event_filter(event, idx, span, sid);
-		smmu_pmu->global_filter_span = span;
-		smmu_pmu->global_filter_sid = sid;
-		return 0;
-	}
+	smmu_pmu_set_event_filter(event, 0, span, sid);
+	smmu_pmu->global_filter_span = span;
+	smmu_pmu->global_filter_sid = sid;

-	return -EAGAIN;
+	return 0;
  }

  static int smmu_pmu_get_event_idx(struct smmu_pmu *smmu_pmu,
-- 
2.20.1.dirty