RE: [PATCH V3 14/14] coresight: etm-perf: Add support for trace buffer format

Al Grant
2021-01-27T13:03:23Z

> > +/* CoreSight PMU AUX buffer formats */
> > +#define PERF_AUX_FLAG_CORESIGHT_FORMAT_CORESIGHT 0x0000 /*
> Default for backward compatibility */
> > +#define PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW 0x0100 /*
> Raw format of the source */
>
> Would CORESIGHT_FORMAT_ETR / CORESIGHT_FORMAT_TRBE be better
> names?

Unformatted (raw) streams could be used any time you had a writer dedicated
to a single trace source. So in a situation where you had one ETR per CPU,
it would be appropriate to use an unformatted stream. A TRBE is always
dedicated to a single CPU, but potentially you (i.e. when designing the system)
can do this with any type of trace sink. So the raw/formatted distinction is
really about whether you are combining multiple streams in one buffer or not,
rather than the type of block that is writing into the buffer.

Al