doc: Document OPAL_GET_PARAM and OPAL_SET_PARAM

Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/doc/device-tree/ibm,opal/sysparams.rst b/doc/device-tree/ibm,opal/sysparams.rst
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+.. _device-tree/ibm,opal/sysparams:
+
+sysparams
+=========
+
+.. code-block:: c
+
+   /* System parameter permission */
+   enum OpalSysparamPerm {
+	OPAL_SYSPARAM_READ  = 0x1,
+	OPAL_SYSPARAM_WRITE = 0x2,
+	OPAL_SYSPARAM_RW    = (OPAL_SYSPARAM_READ | OPAL_SYSPARAM_WRITE),
+   };
+
+
+.. code-block:: dts
+
+   sysparams {
+		compatible = "ibm,opal-sysparams";
+                param-id = <0xf0000001 0xf0000003 0xf0000012 0xf0000016 0xf000001d 0xf0000023 0xf0000024 0xf0000025 0xf0000026 0xf0000027>;
+                param-name = "surveillance", "hmc-management", "cupd-policy", "plat-hmc-managed", "fw-license-policy", "world-wide-port-num", "default-boot-device", "next-boot-device", "console-select", "boot-device-path";
+                param-perm = [03 01 03 03 03 02 03 03 03 03];
+                phandle = <0x10000032>;
+                param-len = <0x4 0x4 0x4 0x4 0x4 0xc 0x1 0x1 0x1 0x30>;
+                linux,phandle = <0x10000032>;
+   };
+
+Device tree node for system parameters accessible through the
+:ref:`opal-sysparams` calls :ref:`OPAL_GET_PARAM` and :ref:`OPAL_SET_PARAM`.
+
+While many systems and platforms will support parameters and configuration via
+either nvram or over IPMI, some platforms may have parameters that need to be
+set a different way.
+
+Some parameters may be set Read Only, so the `param-perm` property indicates
+permissions.
+
+Currently, this is only something that exists on FSP based systems.