perf tests: test_arm_coresight: Simplify source iteration

There are two reasons to do this, firstly there is a shellcheck warning
in cs_etm_dev_name(), which can be completely deleted. And secondly the
current iteration method doesn't support systems with both ETE and ETM
because it picks one or the other. There isn't a known system with this
configuration, but it could happen in the future.

Iterating over all the sources for each CPU can be done by going through
/sys/bus/event_source/devices/cs_etm/cpu* and following the symlink back
to the Coresight device in /sys/bus/coresight/devices. This will work
whether the device is ETE, ETM or any future name, and is much simpler
and doesn't require any hard coded version numbers

Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: James Clark <james.clark@arm.com>
Acked-by: Ian Rogers <irogers@google.com>
Tested-by: Leo Yan <leo.yan@linaro.org>
Cc: tianruidong@linux.alibaba.com
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Anushree Mathur <anushree.mathur@linux.vnet.ibm.com>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: atrajeev@linux.vnet.ibm.com
Cc: coresight@lists.linaro.org
Link: https://lore.kernel.org/r/20231023131550.487760-1-james.clark@arm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Author: James-A-Clark

tools/perf/tests/shell/test_arm_coresight.sh

@@ -11,19 +11,6 @@
 
 glb_err=0
 
-cs_etm_dev_name() {
-	cs_etm_path=$(find  /sys/bus/event_source/devices/cs_etm/ -name cpu* -print -quit)
-	trcdevarch=$(cat ${cs_etm_path}/mgmt/trcdevarch)
-	archhver=$((($trcdevarch >> 12) & 0xf))
-	archpart=$(($trcdevarch & 0xfff))
-
-	if [ $archhver -eq 5 -a "$(printf "0x%X\n" $archpart)" = "0xA13" ] ; then
-		echo "ete"
-	else
-		echo "etm"
-	fi
-}
-
 skip_if_no_cs_etm_event() {
 	perf list | grep -q 'cs_etm//' && return 0
 
@@ -149,7 +136,9 @@ arm_cs_iterate_devices() {
 
 arm_cs_etm_traverse_path_test() {
 	# Iterate for every ETM device
-	for dev in /sys/bus/coresight/devices/$(cs_etm_dev_name)*; do
+	for dev in /sys/bus/event_source/devices/cs_etm/cpu*; do
+		# Canonicalize the path
+		dev=`readlink -f $dev`
 
 		# Find the ETM device belonging to which CPU
 		cpu=`cat $dev/cpu`