1# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2%YAML 1.2
3---
4$id: http://devicetree.org/schemas/mailbox/arm,mhu.yaml#
5$schema: http://devicetree.org/meta-schemas/core.yaml#
6
7title: ARM MHU Mailbox Controller
8
9maintainers:
10  - Jassi Brar <jaswinder.singh@linaro.org>
11
12description: |
13  The ARM's Message-Handling-Unit (MHU) is a mailbox controller that has 3
14  independent channels/links to communicate with remote processor(s).  MHU links
15  are hardwired on a platform. A link raises interrupt for any received data.
16  However, there is no specified way of knowing if the sent data has been read
17  by the remote. This driver assumes the sender polls STAT register and the
18  remote clears it after having read the data.  The last channel is specified to
19  be a 'Secure' resource, hence can't be used by Linux running NS.
20
21  The MHU hardware also allows operations in doorbell mode. The MHU drives the
22  interrupt signal using a 32-bit register, with all 32-bits logically ORed
23  together. It provides a set of registers to enable software to set, clear and
24  check the status of each of the bits of this register independently. The use
25  of 32 bits per interrupt line enables software to provide more information
26  about the source of the interrupt. For example, each bit of the register can
27  be associated with a type of event that can contribute to raising the
28  interrupt. Each of the 32-bits can be used as "doorbell" to alert the remote
29  processor.
30
31# We need a select here so we don't match all nodes with 'arm,primecell'
32select:
33  properties:
34    compatible:
35      contains:
36        enum:
37          - arm,mhu
38          - arm,mhu-doorbell
39  required:
40    - compatible
41
42properties:
43  compatible:
44    oneOf:
45      - description: Data transfer mode
46        items:
47          - const: arm,mhu
48          - const: arm,primecell
49
50      - description: Doorbell mode
51        items:
52          - const: arm,mhu-doorbell
53          - const: arm,primecell
54
55
56  reg:
57    maxItems: 1
58
59  interrupts:
60    minItems: 2
61    items:
62      - description: low-priority non-secure
63      - description: high-priority non-secure
64      - description: Secure
65
66  clocks:
67    maxItems: 1
68
69  clock-names:
70    items:
71      - const: apb_pclk
72
73  '#mbox-cells':
74    description: |
75      Set to 1 in data transfer mode and represents index of the channel.
76      Set to 2 in doorbell mode and represents index of the channel and doorbell
77      number.
78    enum: [ 1, 2 ]
79
80required:
81  - compatible
82  - reg
83  - interrupts
84  - '#mbox-cells'
85
86additionalProperties: false
87
88examples:
89  # Data transfer mode.
90  - |
91    soc {
92        #address-cells = <2>;
93        #size-cells = <2>;
94
95        mhuA: mailbox@2b1f0000 {
96            #mbox-cells = <1>;
97            compatible = "arm,mhu", "arm,primecell";
98            reg = <0 0x2b1f0000 0 0x1000>;
99            interrupts = <0 36 4>, /* LP-NonSecure */
100                         <0 35 4>, /* HP-NonSecure */
101                         <0 37 4>; /* Secure */
102            clocks = <&clock 0 2 1>;
103            clock-names = "apb_pclk";
104        };
105    };
106
107    firmware {
108        scpi {
109            compatible = "arm,scpi";
110            mboxes = <&mhuA 1>; /* HP-NonSecure */
111            shmem = <&cpu_scp_hpri>; /* HP-NonSecure */
112
113            scpi_devpd: power-controller {
114                compatible = "arm,scpi-power-domains";
115                num-domains = <2>;
116                #power-domain-cells = <1>;
117            };
118        };
119    };
120
121  # Doorbell mode.
122  - |
123    soc {
124        #address-cells = <2>;
125        #size-cells = <2>;
126
127        mhuB: mailbox@2b2f0000 {
128            #mbox-cells = <2>;
129            compatible = "arm,mhu-doorbell", "arm,primecell";
130            reg = <0 0x2b2f0000 0 0x1000>;
131            interrupts = <0 36 4>, /* LP-NonSecure */
132                         <0 35 4>, /* HP-NonSecure */
133                         <0 37 4>; /* Secure */
134            clocks = <&clock 0 2 1>;
135            clock-names = "apb_pclk";
136        };
137    };
138
139    firmware {
140        scmi {
141            compatible = "arm,scmi";
142            mboxes = <&mhuB 0 0>, /* LP-NonSecure, 1st doorbell */
143                     <&mhuB 0 1>; /* LP-NonSecure, 2nd doorbell */
144            mbox-names = "tx", "rx";
145            shmem = <&cpu_scp_lpri0>,
146                    <&cpu_scp_lpri1>;
147
148            #address-cells = <1>;
149            #size-cells = <0>;
150
151            scmi_devpd: protocol@11 {
152                reg = <0x11>;
153                #power-domain-cells = <1>;
154            };
155
156            scmi_dvfs: protocol@13 {
157                reg = <0x13>;
158                #clock-cells = <1>;
159
160                mboxes = <&mhuB 1 2>, /* HP-NonSecure, 3rd doorbell */
161                         <&mhuB 1 3>; /* HP-NonSecure, 4th doorbell */
162                mbox-names = "tx", "rx";
163                shmem = <&cpu_scp_hpri0>,
164                        <&cpu_scp_hpri1>;
165            };
166        };
167    };
168
169...
170