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.poir...@linaro.org> > > Cc: Mathieu Poirier <mathieu.poir...@linaro.org> > Cc: Mike Leach <mike.le...@linaro.org> > Cc: Robert Walker <robert.wal...@arm.com> > Signed-off-by: Leo Yan <leo....@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); > decoder->trace_on = false; > break; > case OCSD_GEN_TRC_ELEM_TRACE_ON: > -- > 2.7.4 >
