coresight: introducing a global trace ID function

TraceID values have to be unique for all tracers and
consistent between drivers and user space.  As such
introducing a central function to be used whenever a
traceID value is required.

The patch also account for data traceIDs, which are usually
I(N) + 1.
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight-etm3x.c

@@ -27,6 +27,7 @@
 #include <linux/cpu.h>
 #include <linux/of.h>
 #include <linux/coresight.h>
+#include <linux/coresight-pmu.h>
 #include <linux/amba/bus.h>
 #include <linux/seq_file.h>
 #include <linux/uaccess.h>
@@ -740,11 +741,7 @@ static void etm_init_arch_data(void *info)
 
 static void etm_init_trace_id(struct etm_drvdata *drvdata)
 {
-	/*
-	 * A trace ID of value 0 is invalid, so let's start at some
-	 * random value that fits in 7 bits and go from there.
-	 */
-	drvdata->traceid = 0x10 + drvdata->cpu;
+	drvdata->traceid = coresight_get_trace_id(drvdata->cpu);
 }
 
 static int etm_probe(struct amba_device *adev, const struct amba_id *id)

include/linux/coresight-pmu.h

@@ -19,9 +19,21 @@
 #define _LINUX_CORESIGHT_PMU_H
 
 #define CORESIGHT_ETM_PMU_NAME "cs_etm"
+#define CORESIGHT_ETM_PMU_SEED  0x10
 
 /* ETMv3.5/PTM's ETMCR config bit */
 #define ETM_OPT_CYCACC  12
 #define ETM_OPT_TS      28
 
+static inline int coresight_get_trace_id(int cpu)
+{
+	/*
+	 * A trace ID of value 0 is invalid, so let's start at some
+	 * random value that fits in 7 bits and go from there.  Since
+	 * the common convention is to have data trace IDs be I(N) + 1,
+	 * set instruction trace IDs as a function of the CPU number.
+	 */
+	return (CORESIGHT_ETM_PMU_SEED + (cpu * 2));
+}
+
 #endif