This patch adds device tree binding for ARM Message Handling Unit (MHU) controller version 2. Based on earlier work by Morten Borup Petersen. Co-developed-by: Tushar Khandelwal <tushar.khandelwal@xxxxxxx> Signed-off-by: Tushar Khandelwal <tushar.khandelwal@xxxxxxx> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> --- V2->V3: - compatible is changed to arm-mhuv2-tx/rx. Later version of MHUv2 have an interrupt in the sender mode as well and we can't find if a mailbox is sender or receiver just based on an interrupt anymore. We needed a better way. - arm-mhuv2-mode is renamed to arm,mhuv2-protocols to fit the purpose better. - Minor formatting otherwise. - No longer an RFC. Morten: Please let me know if you want me to add your sign-off here from some other email id as you no longer work with ARM. --- .../bindings/mailbox/arm,mhuv2.yaml | 194 ++++++++++++++++++ 1 file changed, 194 insertions(+) create mode 100644 Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml diff --git a/Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml b/Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml new file mode 100644 index 000000000000..a2b8ecd639c7 --- /dev/null +++ b/Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml @@ -0,0 +1,194 @@ +# 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@xxxxxxx> + - Viresh Kumar <viresh.kumar@xxxxxxxxxx> + +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. + + - 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. + + - Single-word: Each transfer is single word, using a single Channel window. + + - Multi-word: Each transfer is made of two or more words, using two or more + channel windows. + +# 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, 1 is reserved for single-word protocol and 2 is + reserved for multi-word 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. For doorbell protocol this field signifies the + number of 32-bit channel windows that implement the doorbell protocol. For + single-word protocol this field signifies the number of 32-bit channel + windows that implement separate single-word protocol mailbox channels. For + multi-word protocol this field signifies the number of channel windows + used for a multi-word protocol, it should be 2 or more. + + 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 3>, <2 5>, <2 7>; + } + + The above example defines the protocols of an ARM MHUv2 mailbox + controller, where a total of 17 channel windows are used. The first two + windows are used in doorbell protocol (64 doorbells), the next 3 windows + are (separately) used in single-word protocol, and the last two mailbox + channels are used in multi-word protocol of length 5 and 7 channel + windows. + + '#mbox-cells': + description: | + It contains two fields, the first field represents the channel number, + which may be used in doorbell, single-word, or multi-word protocol, and + the second field (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 the arm,mhuv2-protocols, here is how a + client node can reference them. + + mboxes = <&mhu 0 5>; // Mailbox channel 0, doorbell 5. + mboxes = <&mhu 1 7>; // Mailbox channel 1, doorbell 7. + mboxes = <&mhu 2 0>; // Mailbox channel 2, single-word protocol. + mboxes = <&mhu 4 0>; // Mailbox channel 4, single-word protocol. + mboxes = <&mhu 6 0>; // Mailbox channel 6, multi-word protocol with 7 windows. + + const: 2 + +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-tx@2b1f0000 { + #mbox-cells = <2>; + compatible = "arm,mhuv2-tx", "arm,primecell"; + reg = <0 0x2b1f0000 0 0x1000>; + clocks = <&clock 0>; + clock-names = "apb_pclk"; + arm,mhuv2-protocols = <1 5>, <2 2>, <2 5>, <2 7>, <0 2>; + }; + + mhu_rx: mailbox-rx@2b1f1000 { + #mbox-cells = <2>; + compatible = "arm,mhuv2-rx", "arm,primecell"; + reg = <0 0x2b1f1000 0 0x1000>; + clocks = <&clock 0>; + clock-names = "apb_pclk"; + arm,mhuv2-protocols = <1 5>, <2 7>, <0 2>; + }; + + mhu_client: scb@2e000000 { + compatible = "fujitsu,mb86s70-scb-1.0"; + reg = <0 0x2e000000 0 0x4000>; + + mboxes = + //single-word protocol channel 0, mhu-rx + <&mhu_rx 0 0>, + //single-word protocol channel 4, mhu-tx + <&mhu_tx 4 0>, + //multi-word protocol channel 6 with 5 windows, mhu-tx + <&mhu_tx 6 0>, + //doorbell protocol channel 9, doorbell 27, mhu-tx + <&mhu_tx 9 27>; + }; + }; -- 2.25.0.rc1.19.g042ed3e048af
