selftests/powerpc/pmu: Update comment with details to understand auxv_generic_compat_...

auxv_generic_compat_pmu() utility function is to detect whether the
system is having generic compat PMU. The check is based on base platform
value from /proc/self/auxv. Update the comment with details on how auxv
is used to detect the platform.

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250113075858.45137-5-atrajeev@linux.vnet.ibm.com

diff --git a/tools/testing/selftests/powerpc/pmu/sampling_tests/misc.c b/tools/testing/selftests/powerpc/pmu/sampling_tests/misc.c
index 1ba675802ee9ad2654745cae1b6dcb422467e00a..8a538b6182a16f2905e3671035c0f16fcbeb7bb0 100644 (file)
--- a/tools/testing/selftests/powerpc/pmu/sampling_tests/misc.c
+++ b/tools/testing/selftests/powerpc/pmu/sampling_tests/misc.c
@@ -497,6 +497,13 @@ int get_thresh_cmp_val(struct event event)
  * Utility function to check for generic compat PMU
  * by comparing base_platform value from auxv and real
  * PVR value.
+ * auxv_base_platform() func gives information of "base platform"
+ * corresponding to PVR value. Incase, if the distro doesn't
+ * support platform PVR (missing cputable support), base platform
+ * in auxv will have a default value other than the real PVR's.
+ * In this case, ISAv3 PMU (generic compat PMU) will be registered
+ * in the system. auxv_generic_compat_pmu() makes use of the base
+ * platform value from auxv to do this check.
  */
 static bool auxv_generic_compat_pmu(void)
 {