coresight: etm4x: Fix timestamp bit field handling

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 c382ee6 ("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@arm.com>
Fixes: c382ee6 ("arm64/sysreg/tools: Move TRFCR definitions to sysreg")
Signed-off-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20250519174945.2245271-2-leo.yan@arm.com

Author: Leo-Yan

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);
 

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;