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    SubjectRe: [PATCH v3 6/8] perf cs-etm: Treat NO_SYNC element as trace discontinuity
    Em Tue, Dec 11, 2018 at 03:38:26PM +0800, Leo Yan escreveu:
    > 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.


    "In upper case"? Maybe:

    In the former case it causes the insertion of a OCSD_GEN_TRC_ELEM_NO_SYNC
    in the middle of the the tracing stream, but as we were npt handling the
    NO_SYNC element properly which ends up making users miss the
    discontinuity indication"?


    > 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

    can we remove the "but" and "of them" (redundant) above?

    > discontinuous; this patch treats OCSD_GEN_TRC_ELEM_NO_SYNC as trace
    a
    > discontinuity and generates CS_ETM_DISCONTINUITY packet for it, so
    > cs-etm can handle discontinuity for this case, finally it saves the last
    it (way too many "discontinuity")
    > trace data for previous trace block and restart samples for new block.
    >
    > Signed-off-by: Leo Yan <leo.yan@linaro.org>
    > Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
    > Cc: Mike Leach <mike.leach@linaro.org>
    > Cc: Robert Walker <robert.walker@arm.com>
    > ---
    > tools/perf/util/cs-etm-decoder/cs-etm-decoder.c | 1 -
    > 1 file changed, 1 deletion(-)
    >
    > 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 1039f364..bee026e 100644
    > --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
    > +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
    > @@ -410,7 +410,6 @@ 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:
    > - break;
    > case OCSD_GEN_TRC_ELEM_TRACE_ON:
    > resp = cs_etm_decoder__buffer_discontinuity(decoder,
    > trace_chan_id);
    > --
    > 2.7.4

    --

    - Arnaldo

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