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diff --git a/Documentation/firmware-guide/acpi/intel-pmc-mux.rst b/Documentation/firmware-guide/acpi/intel-pmc-mux.rst new file mode 100644 index 000000000000..99b86710f02b --- /dev/null +++ b/Documentation/firmware-guide/acpi/intel-pmc-mux.rst @@ -0,0 +1,153 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================== +Intel North Mux-Agent +===================== + +Introduction +============ + +North Mux-Agent is a function of the Intel PMC firmware that is supported on +most Intel based platforms that have the PMC microcontroller. It's used for +configuring the various USB Multiplexer/DeMultiplexers on the system. The +platforms that allow the mux-agent to be configured from the operating system +have an ACPI device object (node) with HID "INTC105C" that represents it. + +The North Mux-Agent (aka. Intel PMC Mux Control, or just mux-agent) driver +communicates with the PMC microcontroller by using the PMC IPC method +(drivers/platform/x86/intel_scu_ipc.c). The driver registers with the USB Type-C +Mux Class which allows the USB Type-C Controller and Interface drivers to +configure the cable plug orientation and mode (with Alternate Modes). The driver +also registers with the USB Role Class in order to support both USB Host and +Device modes. The driver is located here: drivers/usb/typec/mux/intel_pmc_mux.c. + +Port nodes +========== + +General +------- + +For every USB Type-C connector under the mux-agent control on the system, there +is a separate child node under the PMC mux-agent device node. Those nodes do not +represent the actual connectors, but instead the "channels" in the mux-agent +that are associated with the connectors:: + + Scope (_SB.PCI0.PMC.MUX) + { + Device (CH0) + { + Name (_ADR, 0) + } + + Device (CH1) + { + Name (_ADR, 1) + } + } + +_PLD (Physical Location of Device) +---------------------------------- + +The optional _PLD object can be used with the port (the channel) nodes. If _PLD +is supplied, it should match the connector node _PLD:: + + Scope (_SB.PCI0.PMC.MUX) + { + Device (CH0) + { + Name (_ADR, 0) + Method (_PLD, 0, NotSerialized) + { + /* Consider this as pseudocode. */ + Return (\_SB.USBC.CON0._PLD()) + } + } + } + +Mux-agent specific _DSD Device Properties +----------------------------------------- + +Port Numbers +~~~~~~~~~~~~ + +In order to configure the muxes behind a USB Type-C connector, the PMC firmware +needs to know the USB2 port and the USB3 port that is associated with the +connector. The driver extracts the correct port numbers by reading specific _DSD +device properties named "usb2-port-number" and "usb3-port-number". These +properties have integer value that means the port index. The port index number +is 1's based, and value 0 is illegal. The driver uses the numbers extracted from +these device properties as-is when sending the mux-agent specific messages to +the PMC:: + + Name (_DSD, Package () { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package() { + Package () {"usb2-port-number", 6}, + Package () {"usb3-port-number", 3}, + }, + }) + +Orientation +~~~~~~~~~~~ + +Depending on the platform, the data and SBU lines coming from the connector may +be "fixed" from the mux-agent's point of view, which means the mux-agent driver +should not configure them according to the cable plug orientation. This can +happen for example if a retimer on the platform handles the cable plug +orientation. The driver uses a specific device properties "sbu-orientation" +(SBU) and "hsl-orientation" (data) to know if those lines are "fixed", and to +which orientation. The value that these properties have is a string value, and +it can be one that is defined for the USB Type-C connector orientation: "normal" +or "reversed":: + + Name (_DSD, Package () { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package() { + Package () {"sbu-orientation", "normal"}, + Package () {"hsl-orientation", "normal"}, + }, + }) + +Example ASL +=========== + +The following ASL is an example that shows the mux-agent node, and two +connectors under its control:: + + Scope (_SB.PCI0.PMC) + { + Device (MUX) + { + Name (_HID, "INTC105C") + + Device (CH0) + { + Name (_ADR, 0) + + Name (_DSD, Package () { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package() { + Package () {"usb2-port-number", 6}, + Package () {"usb3-port-number", 3}, + Package () {"sbu-orientation", "normal"}, + Package () {"hsl-orientation", "normal"}, + }, + }) + } + + Device (CH1) + { + Name (_ADR, 1) + + Name (_DSD, Package () { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package() { + Package () {"usb2-port-number", 5}, + Package () {"usb3-port-number", 2}, + Package () {"sbu-orientation", "normal"}, + Package () {"hsl-orientation", "normal"}, + }, + }) + } + } + } |