coresight: Emit sink ID in the HW_ID packets

For Perf to be able to decode when per-sink trace IDs are used, emit the
sink that's being written to for each ETM.

Perf currently errors out if it sees a newer packet version so instead
of bumping it, add a new minor version field. This can be used to
signify new versions that have backwards compatible fields. Considering
this change is only for high core count machines, it doesn't make sense
to make a breaking change for everyone.

Signed-off-by: James Clark <james.clark@arm.com>
Tested-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: James Clark <james.clark@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20240722101202.26915-17-james.clark@linaro.org

Author: James-A-Clark

drivers/hwtracing/coresight/coresight-core.c

@@ -487,23 +487,25 @@ struct coresight_device *coresight_get_sink(struct list_head *path)
 	return csdev;
 }
 
+u32 coresight_get_sink_id(struct coresight_device *csdev)
+{
+	if (!csdev->ea)
+		return 0;
+
+	/*
+	 * See function etm_perf_add_symlink_sink() to know where
+	 * this comes from.
+	 */
+	return (u32) (unsigned long) csdev->ea->var;
+}
+
 static int coresight_sink_by_id(struct device *dev, const void *data)
 {
 	struct coresight_device *csdev = to_coresight_device(dev);
-	unsigned long hash;
 
 	if (csdev->type == CORESIGHT_DEV_TYPE_SINK ||
-	     csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) {
-
-		if (!csdev->ea)
-			return 0;
-		/*
-		 * See function etm_perf_add_symlink_sink() to know where
-		 * this comes from.
-		 */
-		hash = (unsigned long)csdev->ea->var;
-
-		if ((u32)hash == *(u32 *)data)
+	    csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) {
+		if (coresight_get_sink_id(csdev) == *(u32 *)data)
 			return 1;
 	}
 

drivers/hwtracing/coresight/coresight-etm-perf.c

@@ -460,6 +460,7 @@ static void etm_event_start(struct perf_event *event, int flags)
 	struct coresight_device *sink, *csdev = per_cpu(csdev_src, cpu);
 	struct list_head *path;
 	u64 hw_id;
+	u8 trace_id;
 
 	if (!csdev)
 		goto fail;
@@ -512,11 +513,16 @@ static void etm_event_start(struct perf_event *event, int flags)
 	 */
 	if (!cpumask_test_cpu(cpu, &event_data->aux_hwid_done)) {
 		cpumask_set_cpu(cpu, &event_data->aux_hwid_done);
-		hw_id = FIELD_PREP(CS_AUX_HW_ID_VERSION_MASK,
-				   CS_AUX_HW_ID_CURR_VERSION);
-		hw_id |= FIELD_PREP(CS_AUX_HW_ID_TRACE_ID_MASK,
-				    coresight_trace_id_read_cpu_id_map(cpu,
-								       &sink->perf_sink_id_map));
+
+		trace_id = coresight_trace_id_read_cpu_id_map(cpu, &sink->perf_sink_id_map);
+
+		hw_id = FIELD_PREP(CS_AUX_HW_ID_MAJOR_VERSION_MASK,
+				CS_AUX_HW_ID_MAJOR_VERSION);
+		hw_id |= FIELD_PREP(CS_AUX_HW_ID_MINOR_VERSION_MASK,
+				CS_AUX_HW_ID_MINOR_VERSION);
+		hw_id |= FIELD_PREP(CS_AUX_HW_ID_TRACE_ID_MASK, trace_id);
+		hw_id |= FIELD_PREP(CS_AUX_HW_ID_SINK_ID_MASK, coresight_get_sink_id(sink));
+
 		perf_report_aux_output_id(event, hw_id);
 	}
 

drivers/hwtracing/coresight/coresight-priv.h

@@ -148,6 +148,7 @@ int coresight_make_links(struct coresight_device *orig,
 			 struct coresight_device *target);
 void coresight_remove_links(struct coresight_device *orig,
 			    struct coresight_connection *conn);
+u32 coresight_get_sink_id(struct coresight_device *csdev);
 
 #if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM3X)
 extern int etm_readl_cp14(u32 off, unsigned int *val);

include/linux/coresight-pmu.h

@@ -49,12 +49,21 @@
  * Interpretation of the PERF_RECORD_AUX_OUTPUT_HW_ID payload.
  * Used to associate a CPU with the CoreSight Trace ID.
  * [07:00] - Trace ID - uses 8 bits to make value easy to read in file.
- * [59:08] - Unused (SBZ)
- * [63:60] - Version
+ * [39:08] - Sink ID - as reported in /sys/bus/event_source/devices/cs_etm/sinks/
+ *	      Added in minor version 1.
+ * [55:40] - Unused (SBZ)
+ * [59:56] - Minor Version - previously existing fields are compatible with
+ *	      all minor versions.
+ * [63:60] - Major Version - previously existing fields mean different things
+ *	      in new major versions.
  */
 #define CS_AUX_HW_ID_TRACE_ID_MASK	GENMASK_ULL(7, 0)
-#define CS_AUX_HW_ID_VERSION_MASK	GENMASK_ULL(63, 60)
+#define CS_AUX_HW_ID_SINK_ID_MASK	GENMASK_ULL(39, 8)
 
-#define CS_AUX_HW_ID_CURR_VERSION 0
+#define CS_AUX_HW_ID_MINOR_VERSION_MASK	GENMASK_ULL(59, 56)
+#define CS_AUX_HW_ID_MAJOR_VERSION_MASK	GENMASK_ULL(63, 60)
+
+#define CS_AUX_HW_ID_MAJOR_VERSION 0
+#define CS_AUX_HW_ID_MINOR_VERSION 1
 
 #endif