[PATCH v2 1/2] coresight: etm4x: Fix timestamp bit field handling

[James Clark]

On 19/05/2025 6:49 pm, Leo Yan wrote:
> Timestamps in the trace data appear as all zeros on recent kernels,
> although the feature works correctly on old kernels (e.g., v6.12).
> 
> Since commit c382ee674c8b ("arm64/sysreg/tools: Move TRFCR definitions
> to sysreg"), the TRFCR_ELx_TS_{VIRTUAL|GUEST_PHYSICAL|PHYSICAL} macros
> were updated to remove the bit shift. As a result, the driver no longer
> shifts bits when operates the timestamp field.
> 
> Fix this by using the FIELD_PREP() and FIELD_GET() helpers.
> 
> Reported-by: Tamas Zsoldos <tamas.zsoldos at arm.com>
> Fixes: c382ee674c8b ("arm64/sysreg/tools: Move TRFCR definitions to sysreg")
> Signed-off-by: Leo Yan <leo.yan at arm.com>
> ---
>   drivers/hwtracing/coresight/coresight-etm4x-core.c  | 2 +-
>   drivers/hwtracing/coresight/coresight-etm4x-sysfs.c | 4 ++--
>   2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index 6a5898355a83..acb4a58e4bb9 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -1237,7 +1237,7 @@ static void cpu_detect_trace_filtering(struct etmv4_drvdata *drvdata)
>   	 * tracing at the kernel EL and EL0, forcing to use the
>   	 * virtual time as the timestamp.
>   	 */
> -	trfcr = (TRFCR_EL1_TS_VIRTUAL |
> +	trfcr = (FIELD_PREP(TRFCR_EL1_TS_MASK, TRFCR_EL1_TS_VIRTUAL) |
>   		 TRFCR_EL1_ExTRE |
>   		 TRFCR_EL1_E0TRE);
>   
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> index 49d5fb87a74b..ab251865b893 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> @@ -2320,11 +2320,11 @@ static ssize_t ts_source_show(struct device *dev,
>   		goto out;
>   	}
>   
> -	switch (drvdata->trfcr & TRFCR_EL1_TS_MASK) {
> +	val = FIELD_GET(TRFCR_EL1_TS_MASK, drvdata->trfcr);
> +	switch (val) {
>   	case TRFCR_EL1_TS_VIRTUAL:
>   	case TRFCR_EL1_TS_GUEST_PHYSICAL:
>   	case TRFCR_EL1_TS_PHYSICAL:
> -		val = FIELD_GET(TRFCR_EL1_TS_MASK, drvdata->trfcr);
>   		break;
>   	default:
>   		val = -1;

Reviewed-by: James Clark <james.clark at linaro.org>