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+.. _opal-powercap:
+
+OPAL_GET_POWERCAP
+==================
+The OPAL_GET_POWERCAP call retreives current information on the power
+cap.
+
+For each entity that can be power capped, the device tree
+binding indicates what handle should be passed for each of the power cap
+properties (minimum possible, maximum possible, current powercap).
+
+The current power cap must be between the minimium possible and maximum
+possible power cap. The minimum and maximum values are dynamic to allow
+for them possibly being changed by other factors or entities
+(e.g. service processor).
+
+The call can be asynchronus, where the token parameter is used to wait
+for the completion.
+
+Parameters
+----------
+::
+        u32 handle
+        int token
+        u32 *pcap
+
+Returns
+-------
+OPAL_SUCCESS
+  Success
+
+OPAL_PARAMETER
+  Invalid pcap pointer
+
+OPAL_UNSUPPORTED
+  No support for reading powercap sensor
+
+OPAL_HARDWARE
+  Unable to procced due to the current hardware state
+
+OPAL_ASYNC_COMPLETION
+  Request was sent and an async completion message will be sent with
+  token and status of the request.
+
+OPAL_SET_POWERCAP
+============================
+The OPAL_SET_POWERCAP call sets a power cap.
+
+For each entity that can be power capped, the device tree
+binding indicates what handle should be passed for each of the power cap
+properties (minimum possible, maximum possible, current powercap).
+
+The current power cap must be between the minimium possible and maximum
+possible power cap.
+
+You cannot currently set the minimum or maximum power cap, and thus
+OPAL_PERMISSION will be returned if it is attempted to set. In the
+future, this may change - but for now, the correct behaviour for an
+Operating System is to not attempt to set them.
+
+Parameters
+----------
+::
+        u32 handle
+        int token
+        u32 pcap
+
+Returns
+-------
+OPAL_SUCCESS
+  Success
+
+OPAL_PARAMETER
+  Invalid powercap requested beyond powercap limits
+
+OPAL_UNSUPPORTED
+  No support for changing the powercap
+
+OPAL_PERMISSION
+  Hardware cannot take the request
+
+OPAL_ASYNC_COMPLETION
+  Request was sent and an async completion message will be sent with
+  token and status of the request.
+
+OPAL_HARDWARE
+  Unable to procced due to the current hardware state
+
+OPAL_BUSY
+  Previous request in progress
+
+OPAL_INTERNAL_ERROR
+  Error in request response
+
+OPAL_TIMEOUT
+  Timeout in request completion