docs: ABI: sysfs-bus-event_source-devices-hv_gpci: Document processor_bus_topology...

Add details of the new hv-gpci interface file called
"processor_bus_topology" in the ABI documentation.

Reviewed-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230729073455.7918-3-kjain@linux.ibm.com

diff --git a/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_gpci b/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_gpci
index 12e2bf9..ba3f9aa 100644 (file)
--- a/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_gpci
+++ b/Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_gpci
@@ -80,3 +80,35 @@ Contact:     Linux on PowerPC Developer List <linuxppc-dev@lists.ozlabs.org>
 Description:   read only
                This sysfs file exposes the cpumask which is designated to make
                HCALLs to retrieve hv-gpci pmu event counter data.
+
+What:          /sys/devices/hv_gpci/interface/processor_bus_topology
+Date:          July 2023
+Contact:       Linux on PowerPC Developer List <linuxppc-dev@lists.ozlabs.org>
+Description:   admin read only
+               This sysfs file exposes the system topology information by making HCALL
+               H_GET_PERF_COUNTER_INFO. The HCALL is made with counter request value
+               PROCESSOR_BUS_TOPOLOGY(0xD0).
+
+               * This sysfs file will be created only for power10 and above platforms.
+
+               * User needs root privileges to read data from this sysfs file.
+
+               * This sysfs file will be created, only when the HCALL returns "H_SUCCESS",
+                 "H_AUTHORITY" or "H_PARAMETER" as the return type.
+
+                 HCALL with return error type "H_AUTHORITY" can be resolved during
+                 runtime by setting "Enable Performance Information Collection" option.
+
+               * The end user reading this sysfs file must decode the content as per
+                 underlying platform/firmware.
+
+               Possible error codes while reading this sysfs file:
+
+               * "-EPERM" : Partition is not permitted to retrieve performance information,
+                           required to set "Enable Performance Information Collection" option.
+
+               * "-EIO" : Can't retrieve system information because of invalid buffer length/invalid address
+                          or because of some hardware error. Refer to getPerfCountInfo documentation for
+                          more information.
+
+               * "-EFBIG" : System information exceeds PAGE_SIZE.