Messages in this thread | | | From | Mike Leach <> | Date | Wed, 20 Jul 2022 11:53:58 +0100 | Subject | Re: [PATCH v2 12/13] coresight: events: PERF_RECORD_AUX_OUTPUT_HW_ID used for Trace ID |
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Hi Suzuki,
On Wed, 20 Jul 2022 at 10:30, Suzuki K Poulose <suzuki.poulose@arm.com> wrote: > > On 04/07/2022 09:11, Mike Leach wrote: > > Use the perf_report_aux_output_id() call to output the CoreSight trace ID > > and associated CPU as a PERF_RECORD_AUX_OUTPUT_HW_ID record in the > > perf.data file. > > > > Signed-off-by: Mike Leach <mike.leach@linaro.org> > > --- > > drivers/hwtracing/coresight/coresight-etm-perf.c | 10 ++++++++++ > > include/linux/coresight-pmu.h | 14 ++++++++++++++ > > 2 files changed, 24 insertions(+) > > > > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c > > index ad3fdc07c60b..531f5d42272b 100644 > > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c > > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c > > @@ -4,6 +4,7 @@ > > * Author: Mathieu Poirier <mathieu.poirier@linaro.org> > > */ > > > > +#include <linux/bitfield.h> > > #include <linux/coresight.h> > > #include <linux/coresight-pmu.h> > > #include <linux/cpumask.h> > > @@ -437,6 +438,7 @@ static void etm_event_start(struct perf_event *event, int flags) > > struct perf_output_handle *handle = &ctxt->handle; > > struct coresight_device *sink, *csdev = per_cpu(csdev_src, cpu); > > struct list_head *path; > > + u64 hw_id; > > > > if (!csdev) > > goto fail; > > @@ -482,6 +484,11 @@ static void etm_event_start(struct perf_event *event, int flags) > > if (source_ops(csdev)->enable(csdev, event, CS_MODE_PERF)) > > goto fail_disable_path; > > > > + /* output cpu / trace ID in perf record */ > > + hw_id = FIELD_PREP(CS_AUX_HW_ID_VERSION_MASK, CS_AUX_HW_ID_CURR_VERSION) | > > + FIELD_PREP(CS_AUX_HW_ID_TRACE_ID_MASK, coresight_trace_id_get_cpu_id(cpu)); > > + perf_report_aux_output_id(event, hw_id); > > + > > out: > > /* Tell the perf core the event is alive */ > > event->hw.state = 0; > > @@ -600,6 +607,9 @@ static void etm_event_stop(struct perf_event *event, int mode) > > > > /* Disabling the path make its elements available to other sessions */ > > coresight_disable_path(path); > > + > > + /* release the trace ID we read on event start */ > > + coresight_trace_id_put_cpu_id(cpu); > > } > > > > static int etm_event_add(struct perf_event *event, int mode) > > diff --git a/include/linux/coresight-pmu.h b/include/linux/coresight-pmu.h > > index 9f7ee380266b..5572d0e10822 100644 > > --- a/include/linux/coresight-pmu.h > > +++ b/include/linux/coresight-pmu.h > > @@ -7,6 +7,8 @@ > > #ifndef _LINUX_CORESIGHT_PMU_H > > #define _LINUX_CORESIGHT_PMU_H > > > > +#include <linux/bits.h> > > + > > #define CORESIGHT_ETM_PMU_NAME "cs_etm" > > > > /* > > @@ -38,4 +40,16 @@ > > #define ETM4_CFG_BIT_RETSTK 12 > > #define ETM4_CFG_BIT_VMID_OPT 15 > > > > +/* > > + * Interpretation of the PERF_RECORD_AUX_OUTPUT_HW_ID payload. > > + * Used to associate a CPU with the CoreSight Trace ID. > > + * [63:16] - unused SBZ > > + * [15:08] - Trace ID > > + * [07:00] - Version > > Could we please re-arrange the fields, such that it is easier to > comprehend the TraceID looking at the raw trace dump ? Also to > accommodate the future changes. > > e.g, > [15:00] - Trace ID /* For future expansion, if at all */ > [59:16] - RES0 > [63:60] - Trace_ID_Version > > I think we *might* (not sure yet) end up adding "sinkid" when we have > sink specific allocation, so that we can associate the HW_ID of an event > to the "AUXTRACE" record (i.e., trace buffer). >
If we go to per sink trace ID maps, then I can't see how we could avoid needing some sort of ID in here, unless we can determine some other method of specifying which CPUs traced into which trace buffer.
> So if we need to do that we could: > > [15:00] - Trace ID /* For future expansion, if at all */ > [47:16] - Trace Pool ID( == 0 if global, == sink_id if sink based) > [59:48] - RES0 > [63:60] - Trace_ID_Version == 1 > > Or we could adopt the above straight away. >
I wouldn't want to commit to a size for the sink ID yet. And I would leave trace ID at what it is for now (8 bits). Make the fields represent what is and up-version and update when changes are actually required. I think this packet may be a candidate for delivering other trace related info we may need in future - such as the timestamp source that is being worked on?
Mike
> Thoughts ? > > Suzuki > > > + */ > > +#define CS_AUX_HW_ID_VERSION_MASK GENMASK_ULL(7, 0) > > +#define CS_AUX_HW_ID_TRACE_ID_MASK GENMASK_ULL(15, 8) > > + > > +#define CS_AUX_HW_ID_CURR_VERSION 0 > > > > + > > #endif >
-- Mike Leach Principal Engineer, ARM Ltd. Manchester Design Centre. UK
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