1 .. SPDX-License-Identifier: GPL-2.0
2
3 =====================
4 Intel North Mux-Agent
5 =====================
6
7 Introduction
8 ============
9
10 North Mux-Agent is a function of the Intel PMC firmware that is supported on
11 most Intel based platforms that have the PMC microcontroller. It's used for
12 configuring the various USB Multiplexer/DeMultiplexers on the system. The
13 platforms that allow the mux-agent to be configured from the operating system
14 have an ACPI device object (node) with HID "INTC105C" that represents it.
15
16 The North Mux-Agent (aka. Intel PMC Mux Control, or just mux-agent) driver
17 communicates with the PMC microcontroller by using the PMC IPC method
18 (drivers/platform/x86/intel_scu_ipc.c). The driver registers with the USB Type-C
19 Mux Class which allows the USB Type-C Controller and Interface drivers to
20 configure the cable plug orientation and mode (with Alternate Modes). The driver
21 also registers with the USB Role Class in order to support both USB Host and
22 Device modes. The driver is located here: drivers/usb/typec/mux/intel_pmc_mux.c.
23
24 Port nodes
25 ==========
26
27 General
28 -------
29
30 For every USB Type-C connector under the mux-agent control on the system, there
31 is a separate child node under the PMC mux-agent device node. Those nodes do not
32 represent the actual connectors, but instead the "channels" in the mux-agent
33 that are associated with the connectors::
34
35 Scope (_SB.PCI0.PMC.MUX)
36 {
37 Device (CH0)
38 {
39 Name (_ADR, 0)
40 }
41
42 Device (CH1)
43 {
44 Name (_ADR, 1)
45 }
46 }
47
48 _PLD (Physical Location of Device)
49 ----------------------------------
50
51 The optional _PLD object can be used with the port (the channel) nodes. If _PLD
52 is supplied, it should match the connector node _PLD::
53
54 Scope (_SB.PCI0.PMC.MUX)
55 {
56 Device (CH0)
57 {
58 Name (_ADR, 0)
59 Method (_PLD, 0, NotSerialized)
60 {
61 /* Consider this as pseudocode. */
62 Return (\_SB.USBC.CON0._PLD())
63 }
64 }
65 }
66
67 Mux-agent specific _DSD Device Properties
68 -----------------------------------------
69
70 Port Numbers
71 ~~~~~~~~~~~~
72
73 In order to configure the muxes behind a USB Type-C connector, the PMC firmware
74 needs to know the USB2 port and the USB3 port that is associated with the
75 connector. The driver extracts the correct port numbers by reading specific _DSD
76 device properties named "usb2-port-number" and "usb3-port-number". These
77 properties have integer value that means the port index. The port index number
78 is 1's based, and value 0 is illegal. The driver uses the numbers extracted from
79 these device properties as-is when sending the mux-agent specific messages to
80 the PMC::
81
82 Name (_DSD, Package () {
83 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
84 Package() {
85 Package () {"usb2-port-number", 6},
86 Package () {"usb3-port-number", 3},
87 },
88 })
89
90 Orientation
91 ~~~~~~~~~~~
92
93 Depending on the platform, the data and SBU lines coming from the connector may
94 be "fixed" from the mux-agent's point of view, which means the mux-agent driver
95 should not configure them according to the cable plug orientation. This can
96 happen for example if a retimer on the platform handles the cable plug
97 orientation. The driver uses a specific device properties "sbu-orientation"
98 (SBU) and "hsl-orientation" (data) to know if those lines are "fixed", and to
99 which orientation. The value that these properties have is a string value, and
100 it can be one that is defined for the USB Type-C connector orientation: "normal"
101 or "reversed"::
102
103 Name (_DSD, Package () {
104 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
105 Package() {
106 Package () {"sbu-orientation", "normal"},
107 Package () {"hsl-orientation", "normal"},
108 },
109 })
110
111 Example ASL
112 ===========
113
114 The following ASL is an example that shows the mux-agent node, and two
115 connectors under its control::
116
117 Scope (_SB.PCI0.PMC)
118 {
119 Device (MUX)
120 {
121 Name (_HID, "INTC105C")
122
123 Device (CH0)
124 {
125 Name (_ADR, 0)
126
127 Name (_DSD, Package () {
128 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
129 Package() {
130 Package () {"usb2-port-number", 6},
131 Package () {"usb3-port-number", 3},
132 Package () {"sbu-orientation", "normal"},
133 Package () {"hsl-orientation", "normal"},
134 },
135 })
136 }
137
138 Device (CH1)
139 {
140 Name (_ADR, 1)
141
142 Name (_DSD, Package () {
143 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
144 Package() {
145 Package () {"usb2-port-number", 5},
146 Package () {"usb3-port-number", 2},
147 Package () {"sbu-orientation", "normal"},
148 Package () {"hsl-orientation", "normal"},
149 },
150 })
151 }
152 }
153 }
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