[PATCH 2/4] powerpc/topology: Add docs for llc_override

[Shrikanth Hegde <sshegde@linux.ibm.com>]

Provide documentation for the newly introduced debug knob
named as llc_override.

This may help one if they want to experiment with cache aware
scheduling.

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
 Documentation/arch/powerpc/index.rst    |  1 +
 Documentation/arch/powerpc/topology.rst | 27 +++++++++++++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 Documentation/arch/powerpc/topology.rst

diff --git a/Documentation/arch/powerpc/index.rst b/Documentation/arch/powerpc/index.rst
index 40419bea8e10..0f4caf50a9e7 100644
--- a/Documentation/arch/powerpc/index.rst
+++ b/Documentation/arch/powerpc/index.rst
@@ -33,6 +33,7 @@ powerpc
     qe_firmware
     syscall64-abi
     transactional_memory
+    topology
     ultravisor
     vas-api
     vcpudispatch_stats
diff --git a/Documentation/arch/powerpc/topology.rst b/Documentation/arch/powerpc/topology.rst
new file mode 100644
index 000000000000..9ed3cf7ade69
--- /dev/null
+++ b/Documentation/arch/powerpc/topology.rst
@@ -0,0 +1,27 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. _topology:
+
+
+llc_override
+==============
+
+Override the scheduler-visible LLC domain on PowerPC.
+
+Having LLC(last level cache) at MC/PKG helps to experiment with new
+scheduler feature called cache aware scheduling which expects LLC to have
+at least more than 1 core. Scheduler uses notion of LLC for wakeup and
+load balancing decisions.
+
+Accepted values are:
+
+  0    Disable the override and use the platform default.
+  smt  LLC will be at SMT domain.
+  mc   LLC will be at MC domain, including at SMT domains.
+  pkg  LLC will be at PKG domain, including at MC and SMT domains,
+
+Writing a new value rebuilds the scheduler domains. One can check the
+domain flags and look for SD_SHARE_LLC to confirm if it took effect.
+
+Note that this doesn't change HW cache topology. It is only a debug knob
+to experiment with scheduler related functionalities. So set it to sensible
+values. Also note that there is no performance guarantees across the values.
-- 
2.52.0