[PATCH v2 09/13] perf: cs-etm: Update record event to use new Trace ID protocol

[Mike Leach]

Trace IDs are now dynamically allocated.

Previously used the static association algorithm that is no longer
used. The 'cpu * 2 + seed' was outdated and broken for systems with high
core counts (>46). as it did not scale and was broken for larger
core counts.

Trace ID is  as unknown in AUXINFO record, and the ID / CPU association
will now be sent in PERF_RECORD_AUX_OUTPUT_HW_ID record.

Remove legacy Trace ID allocation algorithm.

Signed-off-by: Mike Leach <mike.leach@xxxxxxxxxx>
---
 include/linux/coresight-pmu.h       | 19 +++++++------------
 tools/include/linux/coresight-pmu.h | 19 +++++++------------
 tools/perf/arch/arm/util/cs-etm.c   | 21 ++++++++++++---------
 3 files changed, 26 insertions(+), 33 deletions(-)

diff --git a/include/linux/coresight-pmu.h b/include/linux/coresight-pmu.h
index 4ac5c081af93..9f7ee380266b 100644
--- a/include/linux/coresight-pmu.h
+++ b/include/linux/coresight-pmu.h
@@ -8,7 +8,13 @@
 #define _LINUX_CORESIGHT_PMU_H
 
 #define CORESIGHT_ETM_PMU_NAME "cs_etm"
-#define CORESIGHT_ETM_PMU_SEED  0x10
+
+/*
+ * Metadata now contains an unused trace ID - IDs are transmitted using a
+ * PERF_RECORD_AUX_OUTPUT_HW_ID record.
+ * Value architecturally defined as reserved in CoreSight.
+ */
+#define CS_UNUSED_TRACE_ID 0x7F
 
 /*
  * Below are the definition of bit offsets for perf option, and works as
@@ -32,15 +38,4 @@
 #define ETM4_CFG_BIT_RETSTK	12
 #define ETM4_CFG_BIT_VMID_OPT	15
 
-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
diff --git a/tools/include/linux/coresight-pmu.h b/tools/include/linux/coresight-pmu.h
index 6c2fd6cc5a98..31d007fab3a6 100644
--- a/tools/include/linux/coresight-pmu.h
+++ b/tools/include/linux/coresight-pmu.h
@@ -8,7 +8,13 @@
 #define _LINUX_CORESIGHT_PMU_H
 
 #define CORESIGHT_ETM_PMU_NAME "cs_etm"
-#define CORESIGHT_ETM_PMU_SEED  0x10
+
+/*
+ * Metadata now contains an unused trace ID - IDs are transmitted using a
+ * PERF_RECORD_AUX_OUTPUT_HW_ID record.
+ * Value architecturally defined as reserved in CoreSight.
+ */
+#define CS_UNUSED_TRACE_ID 0x7F
 
 /*
  * Below are the definition of bit offsets for perf option, and works as
@@ -34,15 +40,4 @@
 #define ETM4_CFG_BIT_RETSTK	12
 #define ETM4_CFG_BIT_VMID_OPT	15
 
-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
diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
index 1b54638d53b0..2d68e6a722ed 100644
--- a/tools/perf/arch/arm/util/cs-etm.c
+++ b/tools/perf/arch/arm/util/cs-etm.c
@@ -421,13 +421,16 @@ static int cs_etm_recording_options(struct auxtrace_record *itr,
 	evlist__to_front(evlist, cs_etm_evsel);
 
 	/*
-	 * In the case of per-cpu mmaps, we need the CPU on the
-	 * AUX event.  We also need the contextID in order to be notified
+	 * get the CPU on the sample - need it to associate trace ID in the
+	 * AUX_OUTPUT_HW_ID event, and the AUX event for per-cpu mmaps.
+	 */
+	evsel__set_sample_bit(cs_etm_evsel, CPU);
+
+	/*
+	 * Also the case of per-cpu mmaps, need the contextID in order to be notified
 	 * when a context switch happened.
 	 */
 	if (!perf_cpu_map__empty(cpus)) {
-		evsel__set_sample_bit(cs_etm_evsel, CPU);
-
 		err = cs_etm_set_option(itr, cs_etm_evsel,
 					BIT(ETM_OPT_CTXTID) | BIT(ETM_OPT_TS));
 		if (err)
@@ -633,8 +636,9 @@ static void cs_etm_save_etmv4_header(__u64 data[], struct auxtrace_record *itr,
 
 	/* Get trace configuration register */
 	data[CS_ETMV4_TRCCONFIGR] = cs_etmv4_get_config(itr);
-	/* Get traceID from the framework */
-	data[CS_ETMV4_TRCTRACEIDR] = coresight_get_trace_id(cpu);
+	/* traceID set to unused */
+	data[CS_ETMV4_TRCTRACEIDR] = CS_UNUSED_TRACE_ID;
+
 	/* Get read-only information from sysFS */
 	data[CS_ETMV4_TRCIDR0] = cs_etm_get_ro(cs_etm_pmu, cpu,
 					       metadata_etmv4_ro[CS_ETMV4_TRCIDR0]);
@@ -681,9 +685,8 @@ static void cs_etm_get_metadata(int cpu, u32 *offset,
 		magic = __perf_cs_etmv3_magic;
 		/* Get configuration register */
 		info->priv[*offset + CS_ETM_ETMCR] = cs_etm_get_config(itr);
-		/* Get traceID from the framework */
-		info->priv[*offset + CS_ETM_ETMTRACEIDR] =
-						coresight_get_trace_id(cpu);
+		/* traceID set to unused */
+		info->priv[*offset + CS_ETM_ETMTRACEIDR] = CS_UNUSED_TRACE_ID;
 		/* Get read-only information from sysFS */
 		info->priv[*offset + CS_ETM_ETMCCER] =
 			cs_etm_get_ro(cs_etm_pmu, cpu,
-- 
2.17.1