# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
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%YAML 1.2
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---
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$id: http://devicetree.org/schemas/mailbox/arm,mhu.yaml#
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$schema: http://devicetree.org/meta-schemas/core.yaml#
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title: ARM MHU Mailbox Controller
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maintainers:
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- Jassi Brar <jaswinder.singh@linaro.org>
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description: |
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The ARM's Message-Handling-Unit (MHU) is a mailbox controller that has 3
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independent channels/links to communicate with remote processor(s). MHU links
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are hardwired on a platform. A link raises interrupt for any received data.
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However, there is no specified way of knowing if the sent data has been read
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by the remote. This driver assumes the sender polls STAT register and the
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remote clears it after having read the data. The last channel is specified to
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be a 'Secure' resource, hence can't be used by Linux running NS.
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The MHU hardware also allows operations in doorbell mode. The MHU drives the
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interrupt signal using a 32-bit register, with all 32-bits logically ORed
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together. It provides a set of registers to enable software to set, clear and
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check the status of each of the bits of this register independently. The use
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of 32 bits per interrupt line enables software to provide more information
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about the source of the interrupt. For example, each bit of the register can
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be associated with a type of event that can contribute to raising the
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interrupt. Each of the 32-bits can be used as "doorbell" to alert the remote
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processor.
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# We need a select here so we don't match all nodes with 'arm,primecell'
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select:
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properties:
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compatible:
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contains:
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enum:
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- arm,mhu
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- arm,mhu-doorbell
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required:
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- compatible
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properties:
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compatible:
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oneOf:
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- description: Data transfer mode
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items:
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- const: arm,mhu
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- const: arm,primecell
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- description: Doorbell mode
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items:
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- const: arm,mhu-doorbell
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- const: arm,primecell
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reg:
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maxItems: 1
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interrupts:
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items:
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- description: low-priority non-secure
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- description: high-priority non-secure
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- description: Secure
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maxItems: 3
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clocks:
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maxItems: 1
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clock-names:
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items:
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- const: apb_pclk
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'#mbox-cells':
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description: |
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Set to 1 in data transfer mode and represents index of the channel.
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Set to 2 in doorbell mode and represents index of the channel and doorbell
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number.
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enum: [ 1, 2 ]
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required:
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- compatible
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- reg
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- interrupts
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- '#mbox-cells'
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additionalProperties: false
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examples:
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# Data transfer mode.
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- |
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soc {
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#address-cells = <2>;
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#size-cells = <2>;
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mhuA: mailbox@2b1f0000 {
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#mbox-cells = <1>;
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compatible = "arm,mhu", "arm,primecell";
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reg = <0 0x2b1f0000 0 0x1000>;
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interrupts = <0 36 4>, /* LP-NonSecure */
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<0 35 4>, /* HP-NonSecure */
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<0 37 4>; /* Secure */
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clocks = <&clock 0 2 1>;
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clock-names = "apb_pclk";
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};
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mhu_client_scb: scb@2e000000 {
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compatible = "fujitsu,mb86s70-scb-1.0";
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reg = <0 0x2e000000 0 0x4000>;
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mboxes = <&mhuA 1>; /* HP-NonSecure */
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};
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};
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# Doorbell mode.
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- |
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soc {
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#address-cells = <2>;
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#size-cells = <2>;
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mhuB: mailbox@2b2f0000 {
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#mbox-cells = <2>;
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compatible = "arm,mhu-doorbell", "arm,primecell";
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reg = <0 0x2b2f0000 0 0x1000>;
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interrupts = <0 36 4>, /* LP-NonSecure */
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<0 35 4>, /* HP-NonSecure */
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<0 37 4>; /* Secure */
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clocks = <&clock 0 2 1>;
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clock-names = "apb_pclk";
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};
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mhu_client_scpi: scpi@2f000000 {
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compatible = "arm,scpi";
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reg = <0 0x2f000000 0 0x200>;
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mboxes = <&mhuB 1 4>; /* HP-NonSecure, 5th doorbell */
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};
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};
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