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
7 title: ARM MHU Mailbox Controller
8
9 maintainers:
10 - Jassi Brar <jaswinder.singh@linaro.org>
11
12 description: |
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'
32 select:
33 properties:
34 compatible:
35 contains:
36 enum:
37 - arm,mhu
38 - arm,mhu-doorbell
39 required:
40 - compatible
41
42 properties:
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
80 required:
81 - compatible
82 - reg
83 - interrupts
84 - '#mbox-cells'
85
86 additionalProperties: false
87
88 examples:
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 ...
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