Subject: [PATCH] coresight: etm4x: Fix enabling of cycle accurate tracing in perf.

From: [email-masked] (Mathieu Poirier)
Date: Tue, 3 Jan 2017 09:57:34 -0700

On Mon, Jan 02, 2017 at 10:55:19PM +0000, Mike Leach wrote:
> Using perf record 'cyclacc' option in cs_etm event was not setting up cycle
> accurate trace correctly.
> 
> Corrects bit set in TRCCONFIGR to enable cycle accurate trace.
> Programs TRCCCCTLR with a valid threshold value as required by ETMv4 spec.

This look good - just a tiny blip below.

> 
> Signed-off-by: Mike Leach <[email-masked]>
> ---
>  drivers/hwtracing/coresight/coresight-etm4x.c | 7 +++++--
>  drivers/hwtracing/coresight/coresight-etm4x.h | 1 +
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> index 4db8d6a..07be032 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
> @@ -216,8 +216,11 @@ static int etm4_parse_event_config(struct etmv4_drvdata *drvdata,
>  		goto out;
>  
>  	/* Go from generic option to ETMv4 specifics */
> -	if (attr->config & BIT(ETM_OPT_CYCACC))
> -		config->cfg |= ETMv4_MODE_CYCACC;
> +	if (attr->config & BIT(ETM_OPT_CYCACC)) {
> +		config->cfg |= BIT(4);
> +		/* TRM: Must program this for cycacc to work */
> +		config->ccctlr = ETM_CYC_THRESHOLD_DEFAULT;
> +	}
>  	if (attr->config & BIT(ETM_OPT_TS))
>  		config->cfg |= ETMv4_MODE_TIMESTAMP;
>  
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
> index ba8d3f8..8a62c6c 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.h
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.h
> @@ -146,6 +146,7 @@
>  #define ETM_ARCH_V4			0x40
>  #define ETMv4_SYNC_MASK			0x1F
>  #define ETM_CYC_THRESHOLD_MASK		0xFFF
> +#define ETM_CYC_THRESHOLD_DEFAULT       256

If only to be consistent with the rest of the defines, please write this value
in base-16.

Thanks,
Mathieu

>  #define ETMv4_EVENT_MASK		0xFF
>  #define ETM_CNTR_MAX_VAL		0xFFFF
>  #define ETM_TRACEID_MASK		0x3f
> -- 
> 2.7.4
>