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

[Mark Rutland <mark.rutland@arm.com>]

On Thu, Jul 13, 2023 at 06:37:57PM +0800, Xu Yang wrote:
> 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.

This means that patch 1 is incomplete; please fold this into patch 1.

> 
> Signed-off-by: Xu Yang <xu.yang_2@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;
> +	}

I think as Frank suggested, it would be clearer to have a mask, and I think
this should have a comment:

	/*
	 * Remove the bias applied in ddr_perf_counter_enable().
	 */
	if (pmu->devtype_data->quirks & DDR_CAP_AXI_ID_FILTER_ENHANCED) {
		if (counter == EVENT_CYCLES_COUNTER)
			new_raw_count &= 0x0fffffff;
	}

Thanks,
Mark.

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

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel