new file mode 100644
@@ -0,0 +1,126 @@
+.. SPDX-License-Identifier: GPL-2.0+:
+
+scmi command
+============
+
+Synopsis
+--------
+
+::
+
+ scmi info
+ scmi perm_dev <agent id> <device id> <flags>
+ scmi perm_proto <agent id> <device id> <protocol id> <flags>
+ scmi reset <agent id> <flags>
+
+Description
+-----------
+
+Arm System Control and Management Interface (SCMI hereafter) is a set of
+standardised interfaces to manage system resources, like clocks, power
+domains, pin controls, reset and so on, in a system-wide manner.
+
+An entity which provides those services is called a SCMI firmware (or
+SCMI server if you like) may be placed/implemented by EL3 software or
+by a dedicated system control processor (SCP) or else.
+
+A user of SCMI interfaces, including U-Boot, is called a SCMI agent and
+may issues commands, which are defined in each protocol for specific system
+resources, to SCMI server via a communication channel, called a transport.
+Those interfaces are independent from the server's implementation thanks to
+a transport layer.
+
+For more details, see the `SCMI specification`_.
+
+While most of system resources managed under SCMI protocols are implemented
+and handled as standard U-Boot devices, for example clk_scmi, scmi command
+provides additional management functionality against SCMI server.
+
+scmi info
+~~~~~~~~~
+ Show base information about SCMI server and supported protocols
+
+scmi perm_dev
+~~~~~~~~~~~~~
+ Allow or deny access permission to the device
+
+scmi perm_proto
+~~~~~~~~~~~~~~~
+ Allow or deny access to the protocol on the device
+
+scmi reset
+~~~~~~~~~~
+ Reset the already-configured permissions against the device
+
+Parameters are used as follows:
+
+<agent id>
+ SCMI Agent ID, hex value
+
+<device id>
+ SCMI Device ID, hex value
+
+ Please note that what a device means is not defined
+ in the specification.
+
+<protocol id>
+ SCMI Protocol ID, hex value
+
+ It must not be 0x10 (base protocol)
+
+<flags>
+ Flags to control the action, hex value
+
+ 0 to deny, 1 to allow. The other values are reserved and allowed
+ values may depend on the implemented version of SCMI server in
+ the future. See SCMI specification for more details.
+
+Example
+-------
+
+Obtain basic information about SCMI server:
+
+::
+
+ => scmi info
+ SCMI device: scmi
+ protocol version: 0x20000
+ # of agents: 3
+ 0: platform
+ > 1: OSPM
+ 2: PSCI
+ # of protocols: 4
+ Power domain management
+ Performance domain management
+ Clock management
+ Sensor management
+ vendor: Linaro
+ sub vendor: PMWG
+ impl version: 0x20b0000
+
+Ask for access permission to device#0:
+
+::
+
+ => scmi perm_dev 1 0 1
+
+Reset configurations with all access permission settings retained:
+
+::
+
+ => scmi reset 1 0
+
+Configuration
+-------------
+
+The scmi command is only available if CONFIG_CMD_SCMI=y.
+Default n because this command is mainly for debug purpose.
+
+Return value
+------------
+
+The return value ($?) is set to 0 if the operation succeeded,
+1 if the operation failed or -1 if the operation failed due to
+a syntax error.
+
+.. _`SCMI specification`: https://developer.arm.com/documentation/den0056/e/?lang=en
@@ -94,6 +94,7 @@ Shell commands
cmd/saves
cmd/sbi
cmd/sf
+ cmd/scmi
cmd/scp03
cmd/seama
cmd/setexpr