[PATCH] perf tests: test_arm_coresight: Simplify source iteration

[PATCH] perf tests: test_arm_coresight: Simplify source iteration

[James Clark]

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>
---

This was discussed here previously:
https://lore.kernel.org/all/20230929041133.95355-2-atrajeev@linux.vnet.ibm.com/

I chose not to add a fixes tag like the original because shellcheck
isn't part of the build so it doesn't really fix any real issue yet and
is just a refactor.

 tools/perf/tests/shell/test_arm_coresight.sh | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/tools/perf/tests/shell/test_arm_coresight.sh b/tools/perf/tests/shell/test_arm_coresight.sh
index fe78c4626e45..65dd85207125 100755
--- a/tools/perf/tests/shell/test_arm_coresight.sh
+++ b/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`
-- 
2.34.1

Re: [PATCH] perf tests: test_arm_coresight: Simplify source iteration

[Ian Rogers]

On Mon, Oct 23, 2023 at 6:17 AM James Clark <james.clark@arm.com> wrote:
>
> 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>

Thanks,
Ian

> ---
>
> This was discussed here previously:
> https://lore.kernel.org/all/20230929041133.95355-2-atrajeev@linux.vnet.ibm.com/
>
> I chose not to add a fixes tag like the original because shellcheck
> isn't part of the build so it doesn't really fix any real issue yet and
> is just a refactor.
>
>  tools/perf/tests/shell/test_arm_coresight.sh | 17 +++--------------
>  1 file changed, 3 insertions(+), 14 deletions(-)
>
> diff --git a/tools/perf/tests/shell/test_arm_coresight.sh b/tools/perf/tests/shell/test_arm_coresight.sh
> index fe78c4626e45..65dd85207125 100755
> --- a/tools/perf/tests/shell/test_arm_coresight.sh
> +++ b/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`
> --
> 2.34.1
>

Re: [PATCH] perf tests: test_arm_coresight: Simplify source iteration

[Leo Yan]

On Mon, Oct 23, 2023 at 02:15:49PM +0100, James Clark wrote:
> 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>

Looks good to me.  And I did a test for it:

Tested-by: Leo Yan <leo.yan@linaro.org>

Re: [PATCH] perf tests: test_arm_coresight: Simplify source iteration

[Namhyung Kim]

On Mon, 23 Oct 2023 14:15:49 +0100, James Clark wrote:
> 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
> 
> [...]

Applied to perf-tools-next, thanks!