[Skiboot] [RFC PATCH 6/7] skiboot: Add documentation for nest IMA opal call

[Hemant Kumar]

This patch adds documentation for the the opal call
opal_nest_ima_counters_control().

Signed-off-by: Hemant Kumar <hemant at linux.vnet.ibm.com>
---
 doc/opal-api/opal-nest-ima-counters.rst | 49 +++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 doc/opal-api/opal-nest-ima-counters.rst

diff --git a/doc/opal-api/opal-nest-ima-counters.rst b/doc/opal-api/opal-nest-ima-counters.rst
new file mode 100644
index 0000000..737c523
--- /dev/null
+++ b/doc/opal-api/opal-nest-ima-counters.rst
@@ -0,0 +1,49 @@
+OPAL_NEST_IMA_COUNTERS_CONTROL
+==============================
+
+OPAL call interface for per-chip nest instrumentation support.
+Currently, the interface supports start and stop of pore slw ima
+(Power On Reset Engine SLeep Wink In Memory Accumulator) engine for
+nest instrumentation from Host OS.
+
+The interface can be extended to include more modes and operations, if
+needed.
+
+Parameters
+----------
+``uint64_t mode``
+  Currently, only production mode is supported.
+  The "NEST_IMA_PRODUCTION_MODE" macro defined in "nest.h"
+  is used for this.
+
+``uint64_t operation``
+  For "NEST_IMA_PRODUCTION_MODE" mode, this parameter is used
+  to start and stop the pore_slw_ima engine.
+
+  - 0x0 -- Stop
+  - 0x1 -- Start
+
+  For other modes, this parameter is undefined for now.
+
+``uint64_t value_1``
+  - For "NEST_IMA_PRODUCTION_MODE" mode, this parameter should be
+    zero.
+  - For other modes, this parameter is undefined for now.
+
+``uint64_t value_3``
+  - For "NEST_IMA_PRODUCTION_MODE" mode, this parameter should be
+    zero.
+  - For other modes, this parameter is undefined for now.
+
+Returns
+-------
+OPAL_PARAMETER
+  In any one/some/all of the following cases :
+
+  - Unsupported ``mode``
+  - Unsupported ``operation``
+  - Non-zero ``value_1`` or ``value_2``
+OPAL_HARDWARE
+   If xscom_write fails.
+OPAL_SUCCESS
+   On successful execution of the ``operation`` in the given ``mode``.
-- 
2.7.4