linux-kernel - Re: [PATCH v8 5/8] perf: imx_perf: fix counter start and config sequence

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Date: Fri, 22 Mar 2024 10:32:50 -0400
From: Frank Li <Frank.li@....com>
To: Xu Yang <xu.yang_2@....com>
Cc: will@...nel.org, mark.rutland@....com, robh+dt@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
	shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
	festevam@...il.com, john.g.garry@...cle.com, jolsa@...nel.org,
	namhyung@...nel.org, irogers@...gle.com, mike.leach@...aro.org,
	peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
	alexander.shishkin@...ux.intel.com, adrian.hunter@...el.com,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
	imx@...ts.linux.dev
Subject: Re: [PATCH v8 5/8] perf: imx_perf: fix counter start and config
 sequence

On Fri, Mar 22, 2024 at 02:39:27PM +0800, Xu Yang wrote:
> In current driver, the counter will start firstly and then be configured.
> This sequence is not correct for AXI filter events since the correct
> AXI_MASK and AXI_ID are not set yet. Then the results may be inaccurate.
> 
> Fixes: 55691f99d417 ("drivers/perf: imx_ddr: Add support for NXP i.MX9 SoC DDRC PMU driver")
> cc: <stable@...r.kernel.org>
> Signed-off-by: Xu Yang <xu.yang_2@....com>

Reviewed-by: Frank Li <Frank.Li@....com>

> 
> ---
> Changes in v5:
>  - new patch
> Changes in v6:
>  - no changes
> Changes in v7:
>  - no changes
> Changes in v8:
>  - add fix tag
> ---
>  drivers/perf/fsl_imx9_ddr_perf.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/perf/fsl_imx9_ddr_perf.c b/drivers/perf/fsl_imx9_ddr_perf.c
> index 011377c01dea..fab6596d3e28 100644
> --- a/drivers/perf/fsl_imx9_ddr_perf.c
> +++ b/drivers/perf/fsl_imx9_ddr_perf.c
> @@ -539,12 +539,12 @@ static int ddr_perf_event_add(struct perf_event *event, int flags)
>  	hwc->idx = counter;
>  	hwc->state |= PERF_HES_STOPPED;
>  
> -	if (flags & PERF_EF_START)
> -		ddr_perf_event_start(event, flags);
> -
>  	/* read trans, write trans, read beat */
>  	imx93_ddr_perf_monitor_config(pmu, event_id, counter, cfg1, cfg2);
>  
> +	if (flags & PERF_EF_START)
> +		ddr_perf_event_start(event, flags);
> +
>  	return 0;
>  }
>  
> -- 
> 2.34.1
>