On Mon, Dec 10, 2018 at 04:52:59PM +0800, Leo Yan wrote:
CoreSight tracer driver might insert barrier packet between different buffers, thus the decoder can spot the boundaries based on the barrier packet; the decoder is possible to hit a barrier packet and emit a NO_SYNC element, then the decoder will find a periodic synchronisation point inside that next trace block that starts trace again but does not have the TRACE_ON element as indicator - usually because this block of trace has wrapped the buffer so we have lost the original point that trace was enabled.
In upper case, it results in the trace stream only inserts the OCSD_GEN_TRC_ELEM_NO_SYNC element in the middle of tracing stream, but we don't handle NO_SYNC element properly and at the end users miss to see the info for trace discontinuity.
Though OCSD_GEN_TRC_ELEM_NO_SYNC is different from CS_ETM_TRACE_ON when output from the decoder, but both of them indicate the trace data is discontinuous; this patch treats OCSD_GEN_TRC_ELEM_NO_SYNC as trace discontinuity and generates CS_ETM_DISCONTINUITY packet for it, so cs-etm can handle discontinuity for this case, finally it saves the last trace data for previous trace block and restart samples for new block.
Credit to Mike Leach and Robert Walker who made me clear for underlying mechanism for NO_SYNC element, Mike also shared with me for detailed explanation for why we can treat NO_SYNC and TRACE_ON elements as the same, so this commit log reused most of his explanation.
Credit and thank you note such as this one go in the cover letter. With this change:
Reviewed-by: Mathieu Poirier mathieu.poirier@linaro.org
Cc: Mathieu Poirier mathieu.poirier@linaro.org Cc: Mike Leach mike.leach@linaro.org Cc: Robert Walker robert.walker@arm.com Signed-off-by: Leo Yan leo.yan@linaro.org
tools/perf/util/cs-etm-decoder/cs-etm-decoder.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c index a3994f1..46b67f1 100644 --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c @@ -411,6 +411,8 @@ static ocsd_datapath_resp_t cs_etm_decoder__gen_trace_elem_printer( case OCSD_GEN_TRC_ELEM_UNKNOWN: break; case OCSD_GEN_TRC_ELEM_NO_SYNC:
resp = cs_etm_decoder__buffer_discontinuity(decoder,trace_chan_id);-- 2.7.4