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Subject[PATCH V4] dt-bindings: mailbox : arm,mhuv2: Add bindings
Date
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@arm.com>
Signed-off-by: Tushar Khandelwal <tushar.khandelwal@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

---
V3->V4:
- Made interrupts property compulsory for receiver
- Added interrupts for both nodes in example
- Fixed min/max items for protocols property
- Don't add -tx/rx to node's name.

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.

Morten: Please let me know if you want me to add your signoff here from
some other email id as you no longer work with ARM.
---
.../bindings/mailbox/arm,mhuv2.yaml | 215 ++++++++++++++++++
1 file changed, 215 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..013b7aeda713
--- /dev/null
+++ b/Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml
@@ -0,0 +1,215 @@
+# 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.
+
+ - 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.
+
+ minItems: 1
+ maxItems: 124
+ items:
+ items:
+ - enum: [ 0, 1, 2 ]
+ - minimum: 0
+ maximum: 124
+
+
+ '#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
+
+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>, <2 2>, <2 5>, <2 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 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
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