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+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mailbox/arm,mhuv2.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ARM MHUv2 Mailbox Controller
+
+maintainers:
+ - Tushar Khandelwal <tushar.khandelwal@arm.com>
+ - Viresh Kumar <viresh.kumar@linaro.org>
+
+description: |
+ The Arm Message Handling Unit (MHU) Version 2 is a mailbox controller that has
+ between 1 and 124 channel windows (each 32-bit wide) to provide unidirectional
+ communication with remote processor(s), where the number of channel windows
+ are implementation dependent.
+
+ Given the unidirectional nature of the controller, an MHUv2 mailbox may only
+ be written to or read from. If a pair of MHU controllers is implemented
+ between two processing elements to provide bidirectional communication, these
+ must be specified as two separate mailboxes.
+
+ If the interrupts property is present in device tree node, then its treated as
+ a "receiver" mailbox, otherwise a "sender".
+
+ An MHU controller must be specified along with the supported transport
+ protocols. The transport protocols determine the method of data transmission
+ as well as the number of provided mailbox channels.
+
+ Following are the possible transport protocols.
+
+ - Data-transfer: Each transfer is made of one or more words, using one or more
+ channel windows.
+
+ - Doorbell: Each transfer is made up of single bit flag, using any one of the
+ bits in a channel window. A channel window can support up to 32 doorbells
+ and the entire window shall be used in doorbell protocol. Optionally, data
+ may be transmitted through a shared memory region, wherein the MHU is used
+ strictly as an interrupt generation mechanism but that is out of the scope
+ of these bindings.
+
+# We need a select here so we don't match all nodes with 'arm,primecell'
+select:
+ properties:
+ compatible:
+ contains:
+ enum:
+ - arm,mhuv2-tx
+ - arm,mhuv2-rx
+ required:
+ - compatible
+
+properties:
+ compatible:
+ oneOf:
+ - description: Sender mode
+ items:
+ - const: arm,mhuv2-tx
+ - const: arm,primecell
+
+ - description: Receiver-mode
+ items:
+ - const: arm,mhuv2-rx
+ - const: arm,primecell
+
+ reg:
+ maxItems: 1
+
+ interrupts:
+ description: |
+ The MHUv2 controller always implements an interrupt in the "receiver"
+ mode, while the interrupt in the "sender" mode was not available in the
+ version MHUv2.0, but the later versions do have it.
+ maxItems: 1
+
+ clocks:
+ maxItems: 1
+
+ clock-names:
+ maxItems: 1
+
+ arm,mhuv2-protocols:
+ $ref: /schemas/types.yaml#/definitions/uint32-matrix
+ description: |
+ The MHUv2 controller may contain up to 124 channel windows (each 32-bit
+ wide). The hardware and the DT bindings allows any combination of those to
+ be used for various transport protocols.
+
+ This property allows a platform to describe how these channel windows are
+ used in various transport protocols. The entries in this property shall be
+ present as an array of tuples, where each tuple describes details about
+ one of the transport protocol being implemented over some channel
+ window(s).
+
+ The first field of a tuple signifies the transfer protocol, 0 is reserved
+ for doorbell protocol, and 1 is reserved for data-transfer protocol.
+ Using any other value in the first field of a tuple makes it invalid.
+
+ The second field of a tuple signifies the number of channel windows where
+ the protocol would be used and should be set to a non zero value. For
+ doorbell protocol this field signifies the number of 32-bit channel
+ windows that implement the doorbell protocol. For data-transfer protocol,
+ this field signifies the number of 32-bit channel windows that implement
+ the data-transfer protocol.
+
+ The total number of channel windows specified here shouldn't be more than
+ the ones implemented by the platform, though one can specify lesser number
+ of windows here than what the platform implements.
+
+ mhu: mailbox@2b1f0000 {
+ ...
+
+ arm,mhuv2-protocols = <0 2>, <1 1>, <1 5>, <1 7>;
+ }
+
+ The above example defines the protocols of an ARM MHUv2 mailbox
+ controller, where a total of 15 channel windows are used. The first two
+ windows are used in doorbell protocol (64 doorbells), followed by 1, 5 and
+ 7 windows (separately) used in data-transfer protocol.
+
+ minItems: 1
+ maxItems: 124
+ items:
+ items:
+ - enum: [ 0, 1 ]
+ - minimum: 0
+ maximum: 124
+
+
+ '#mbox-cells':
+ description: |
+ It is always set to 2. The first argument in the consumers 'mboxes'
+ property represents the channel window group, which may be used in
+ doorbell, or data-transfer protocol, and the second argument (only
+ relevant in doorbell protocol, should be 0 otherwise) represents the
+ doorbell number within the 32 bit wide channel window.
+
+ From the example given above for arm,mhuv2-protocols, here is how a client
+ node can reference them.
+
+ mboxes = <&mhu 0 5>; // Channel Window Group 0, doorbell 5.
+ mboxes = <&mhu 1 7>; // Channel Window Group 1, doorbell 7.
+ mboxes = <&mhu 2 0>; // Channel Window Group 2, data transfer protocol with 1 window.
+ mboxes = <&mhu 3 0>; // Channel Window Group 3, data transfer protocol with 5 windows.
+ mboxes = <&mhu 4 0>; // Channel Window Group 4, data transfer protocol with 7 windows.
+
+ const: 2
+
+if:
+ # Interrupt is compulsory for receiver
+ properties:
+ compatible:
+ contains:
+ const: arm,mhuv2-rx
+then:
+ required:
+ - interrupts
+
+required:
+ - compatible
+ - reg
+ - '#mbox-cells'
+ - arm,mhuv2-protocols
+
+additionalProperties: false
+
+examples:
+ # Multiple transport protocols implemented by the mailbox controllers
+ - |
+ soc {
+ #address-cells = <2>;
+ #size-cells = <2>;
+
+ mhu_tx: mailbox@2b1f0000 {
+ #mbox-cells = <2>;
+ compatible = "arm,mhuv2-tx", "arm,primecell";
+ reg = <0 0x2b1f0000 0 0x1000>;
+ clocks = <&clock 0>;
+ clock-names = "apb_pclk";
+ interrupts = <0 45 4>;
+ arm,mhuv2-protocols = <1 5>, <1 2>, <1 5>, <1 7>, <0 2>;
+ };
+
+ mhu_rx: mailbox@2b1f1000 {
+ #mbox-cells = <2>;
+ compatible = "arm,mhuv2-rx", "arm,primecell";
+ reg = <0 0x2b1f1000 0 0x1000>;
+ clocks = <&clock 0>;
+ clock-names = "apb_pclk";
+ interrupts = <0 46 4>;
+ arm,mhuv2-protocols = <1 1>, <1 7>, <0 2>;
+ };
+
+ mhu_client: scb@2e000000 {
+ compatible = "fujitsu,mb86s70-scb-1.0";
+ reg = <0 0x2e000000 0 0x4000>;
+
+ mboxes =
+ //data-transfer protocol with 5 windows, mhu-tx
+ <&mhu_tx 2 0>,
+ //data-transfer protocol with 7 windows, mhu-tx
+ <&mhu_tx 3 0>,
+ //doorbell protocol channel 4, doorbell 27, mhu-tx
+ <&mhu_tx 4 27>,
+ //data-transfer protocol with 1 window, mhu-rx
+ <&mhu_rx 0 0>;
+ };
+ };