[PATCH v4 0/1] perf: cs_etm: Allow no sink on command line.

From: Mike Leach
Date: Tue May 26 2020 - 06:53:18 EST

Currently starting CoreSight tracing using perf requires a sink selection
on the command line:-

sudo ./perf record -e cs_etm/@tmc_etr0/ --per-thread uname -a

Not providing the @<sink> here results in an error and no trace produced.

After this set (alongside the CoreSight change set [1]) the infrastructure
will be able to select a default sink:-

sudo ./perf record -e cs_etm// --per-thread uname -a

This matches with the default operation provided with perf and intelpt.

This patch removes the check that a sink value is provided on the command
line with a NULL value passed to the CoreSight infrastructure if omitted.

Note: If this set is applied to a system without [1], then the effect is
benign as the existing CoreSight infrastructure will detect the error and
refuse to trace.

Applies to Linux coresight/next branch

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2020-May/734854.html

Changes since v3:
1) Removed RFC designation and distributed to wider audience.
2) Split set into perf user runtime (this set), and CoreSight driver code.

Mike Leach (1):
perf: cs-etm: Allow no CoreSight sink to be specified on command line

tools/perf/arch/arm/util/cs-etm.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)