[PATCH] Documentation: admin-guide: pm: Add Out of Band mode

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

Update documentation for using the tool to support performance level
change via OOB (Out of Band) interface.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
 .../admin-guide/pm/intel-speed-select.rst     | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/Documentation/admin-guide/pm/intel-speed-select.rst b/Documentation/admin-guide/pm/intel-speed-select.rst
index 0a1fbdb54bfe..4146a2da35ea 100644
--- a/Documentation/admin-guide/pm/intel-speed-select.rst
+++ b/Documentation/admin-guide/pm/intel-speed-select.rst
@@ -262,6 +262,25 @@ Which shows that the base frequency now increased from 2600 MHz at performance
 level 0 to 2800 MHz at performance level 4. As a result, any workload, which can
 use fewer CPUs, can see a boost of 200 MHz compared to performance level 0.
 
+Changing performance level via BMC Interface
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+It is possible to change SST-PP level using out of band (OOB) agent (Via some
+remote management console, through BMC "Baseboard Management Controller"
+interface). This mode is supported from the Sapphire Rapids processor
+generation. The kernel and tool change to support this mode is added to Linux
+kernel version 5.18. To enable this feature, kernel config
+"CONFIG_INTEL_HFI_THERMAL" is required. The minimum version of the tool
+is "v1.12" to support this feature, which is part of Linux kernel version 5.18.
+
+To support such configuration, this tool can be used as a daemon. Add
+a command line option --oob::
+
+# intel-speed-select --oob
+
+In this mode the tool will online/offline CPUs based on the new performance
+level.
+
 Check presence of other Intel(R) SST features
 ---------------------------------------------
 
-- 
2.35.1