linux-kernel - [PATCH v4 02/19] perf: aux: Add CoreSight PMU buffer formats

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Date:   Thu, 25 Feb 2021 19:35:26 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, mathieu.poirier@...aro.org,
        mike.leach@...aro.org, anshuman.khandual@....com,
        leo.yan@...aro.org, Suzuki K Poulose <suzuki.poulose@....com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH v4 02/19] perf: aux: Add CoreSight PMU buffer formats

CoreSight PMU supports aux-buffer for the ETM tracing. The trace
generated by the ETM (associated with individual CPUs, like Intel PT)
is captured by a separate IP (CoreSight TMC-ETR/ETF until now).

The TMC-ETR applies formatting of the raw ETM trace data, as it
can collect traces from multiple ETMs, with the TraceID to indicate
the source of a given trace packet.

Arm Trace Buffer Extension is new "sink" IP, attached to individual
CPUs and thus do not provide additional formatting, like TMC-ETR.

Additionally, a system could have both TRBE *and* TMC-ETR for
the trace collection. e.g, TMC-ETR could be used as a single
trace buffer to collect data from multiple ETMs to correlate
the traces from different CPUs. It is possible to have a
perf session where some events end up collecting the trace
in TMC-ETR while the others in TRBE. Thus we need a way
to identify the type of the trace for each AUX record.

Define the trace formats exported by the CoreSight PMU.
We don't define the flags following the "ETM" as this
information is available to the user when issuing
the session. What is missing is the additional
formatting applied by the "sink" which is decided
at the runtime and the user may not have a control on.

So we define :
 - CORESIGHT format (indicates the Frame format)
 - RAW format (indicates the format of the source)

The default value is CORESIGHT format for all the records
(i,e == 0). Add the RAW format for others that use
raw format.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Mike Leach <mike.leach@...aro.org>
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Leo Yan <leo.yan@...aro.org>
Cc: Anshuman Khandual <anshuman.khandual@....com>
Reviewed-by: Mike Leach <mike.leach@...aro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
Changes from previous:
 - Split from the coresight driver specific code
   for ease of merging
---
 include/uapi/linux/perf_event.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index f006eeab6f0e..63971eaef127 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -1162,6 +1162,10 @@ enum perf_callchain_context {
 #define PERF_AUX_FLAG_COLLISION			0x08	/* sample collided with another */
 #define PERF_AUX_FLAG_PMU_FORMAT_TYPE_MASK	0xff00	/* PMU specific trace format type */

+/* CoreSight PMU AUX buffer formats */
+#define PERF_AUX_FLAG_CORESIGHT_FORMAT_CORESIGHT	0x0000 /* Default for backward compatibility */
+#define PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW		0x0100 /* Raw format of the source */
+
 #define PERF_FLAG_FD_NO_GROUP		(1UL << 0)
 #define PERF_FLAG_FD_OUTPUT		(1UL << 1)
 #define PERF_FLAG_PID_CGROUP		(1UL << 2) /* pid=cgroup id, per-cpu mode only */
-- 
2.24.1