[PATCH v2 2/3] perf/imx_ddr: adjust counter result after read cycle counter

[Frank Li]

> -----Original Message-----
> From: Xu Yang <xu.yang_2 at nxp.com>
> Sent: Thursday, July 13, 2023 5:38 AM
> To: Frank Li <frank.li at nxp.com>
> Cc: will at kernel.org; mark.rutland at arm.com; shawnguo at kernel.org;
> s.hauer at pengutronix.de; kernel at pengutronix.de; dl-linux-imx <linux-
> imx at nxp.com>; linux-arm-kernel at lists.infradead.org
> Subject: [PATCH v2 2/3] perf/imx_ddr: adjust counter result after read cycle
> counter
> 
> Because we initialize CP filed to shorten counter0 overflow time, the cycle
> counter will start couting from a fixed/base value each time. We need to
> remove the base from the result too. Therefore, we could get precise result
> from cycle counter.
> 
> Signed-off-by: Xu Yang <xu.yang_2 at nxp.com>
> 
> ---
> Changes in v2:
>  - improve if condition
> ---
>  drivers/perf/fsl_imx8_ddr_perf.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/perf/fsl_imx8_ddr_perf.c
> b/drivers/perf/fsl_imx8_ddr_perf.c
> index 039069756bbc..d65200d4e96e 100644
> --- a/drivers/perf/fsl_imx8_ddr_perf.c
> +++ b/drivers/perf/fsl_imx8_ddr_perf.c
> @@ -481,6 +481,12 @@ static void ddr_perf_event_update(struct
> perf_event *event)
>  	int ret;
> 
>  	new_raw_count = ddr_perf_read_counter(pmu, counter);
> +	/* Workaround for i.MX8MP */
> +	if (pmu->devtype_data->quirks &
> DDR_CAP_AXI_ID_FILTER_ENHANCED) {
> +		if (counter == EVENT_CYCLES_COUNTER)
> +			new_raw_count -= 0xF0000000;

[Frank Li] Do you means
	new_raw_count &= 0x0FFFFFFF? to mask bit 24..31?

> +	}
> +
>  	local64_add(new_raw_count, &event->count);
> 
>  	/*
> --
> 2.34.1