[PATCH] coresight: etm4x: Fix timestamp bit field handling

[Leo Yan]

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. Simplify the
ts_source_show() function: return -1 when the value is zero, as this
indciates an invalid value; otherwise return the decoded TS value
directly.

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>
---
 .../hwtracing/coresight/coresight-etm4x-core.c  |  2 +-
 .../hwtracing/coresight/coresight-etm4x-sysfs.c | 17 ++---------------
 2 files changed, 3 insertions(+), 16 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..8a2749eeb9a5 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
@@ -2315,23 +2315,10 @@ static ssize_t ts_source_show(struct device *dev,
 	int val;
 	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
 
-	if (!drvdata->trfcr) {
+	val = FIELD_GET(TRFCR_EL1_TS_MASK, drvdata->trfcr);
+	if (!val)
 		val = -1;
-		goto out;
-	}
-
-	switch (drvdata->trfcr & TRFCR_EL1_TS_MASK) {
-	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;
-		break;
-	}
 
-out:
 	return sysfs_emit(buf, "%d\n", val);
 }
 static DEVICE_ATTR_RO(ts_source);
-- 
2.34.1