1 files changed, 8 insertions, 12 deletions

diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
index 6e03db142091..872fab163585 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
@@ -251,19 +251,15 @@ struct intel_pt_decoder *intel_pt_decoder_new(struct intel_pt_params *params)
                 if (!(decoder->tsc_ctc_ratio_n % decoder->tsc_ctc_ratio_d))
                         decoder->tsc_ctc_mult = decoder->tsc_ctc_ratio_n /
                                                 decoder->tsc_ctc_ratio_d;
-
-                /*
-                 * Allow for timestamps appearing to backwards because a TSC
-                 * packet has slipped past a MTC packet, so allow 2 MTC ticks
-                 * or ...
-                 */
-                decoder->tsc_slip = multdiv(2 << decoder->mtc_shift,
-                                        decoder->tsc_ctc_ratio_n,
-                                        decoder->tsc_ctc_ratio_d);
         }
-        /* ... or 0x100 paranoia */
-        if (decoder->tsc_slip < 0x100)
-                decoder->tsc_slip = 0x100;
+
+        /*
+         * A TSC packet can slip past MTC packets so that the timestamp appears
+         * to go backwards. One estimate is that can be up to about 40 CPU
+         * cycles, which is certainly less than 0x1000 TSC ticks, but accept
+         * slippage an order of magnitude more to be on the safe side.
+         */
+        decoder->tsc_slip = 0x10000;
 
         intel_pt_log("timestamp: mtc_shift %u\n", decoder->mtc_shift);
         intel_pt_log("timestamp: tsc_ctc_ratio_n %u\n", decoder->tsc_ctc_ratio_n);