1.. SPDX-License-Identifier: GPL-2.0
2
3=====================
4Intel North Mux-Agent
5=====================
6
7Introduction
8============
9
10North Mux-Agent is a function of the Intel PMC firmware that is supported on
11most Intel based platforms that have the PMC microcontroller. It's used for
12configuring the various USB Multiplexer/DeMultiplexers on the system. The
13platforms that allow the mux-agent to be configured from the operating system
14have an ACPI device object (node) with HID "INTC105C" that represents it.
15
16The North Mux-Agent (aka. Intel PMC Mux Control, or just mux-agent) driver
17communicates 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
19Mux Class which allows the USB Type-C Controller and Interface drivers to
20configure the cable plug orientation and mode (with Alternate Modes). The driver
21also registers with the USB Role Class in order to support both USB Host and
22Device modes. The driver is located here: drivers/usb/typec/mux/intel_pmc_mux.c.
23
24Port nodes
25==========
26
27General
28-------
29
30For every USB Type-C connector under the mux-agent control on the system, there
31is a separate child node under the PMC mux-agent device node. Those nodes do not
32represent the actual connectors, but instead the "channels" in the mux-agent
33that 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
51The optional _PLD object can be used with the port (the channel) nodes. If _PLD
52is 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
67Mux-agent specific _DSD Device Properties
68-----------------------------------------
69
70Port Numbers
71~~~~~~~~~~~~
72
73In order to configure the muxes behind a USB Type-C connector, the PMC firmware
74needs to know the USB2 port and the USB3 port that is associated with the
75connector. The driver extracts the correct port numbers by reading specific _DSD
76device properties named "usb2-port-number" and "usb3-port-number". These
77properties have integer value that means the port index. The port index number
78is 1's based, and value 0 is illegal. The driver uses the numbers extracted from
79these device properties as-is when sending the mux-agent specific messages to
80the 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
90Orientation
91~~~~~~~~~~~
92
93Depending on the platform, the data and SBU lines coming from the connector may
94be "fixed" from the mux-agent's point of view, which means the mux-agent driver
95should not configure them according to the cable plug orientation. This can
96happen for example if a retimer on the platform handles the cable plug
97orientation. The driver uses a specific device properties "sbu-orientation"
98(SBU) and "hsl-orientation" (data) to know if those lines are "fixed", and to
99which orientation. The value that these properties have is a string value, and
100it can be one that is defined for the USB Type-C connector orientation: "normal"
101or "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
111Example ASL
112===========
113
114The following ASL is an example that shows the mux-agent node, and two
115connectors 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	}
154