bindings: usb_bam: Add USB BAM driver related documentation

MSM USB Bus Access Manager (BAM)

This describes the device used to interface the USB controller

with the Smart Peripheral Subsystem (SPS). The BAM serves to

connect USB directly with other peer peripherals in the system

and is statically configured with a number of unidirectional pipes.

Required properties:

- compatible: should be "qcom,usb-bam-msm"

- reg  : pair of physical base addresses and region size of BAM device

- interrupts: IRQ line for BAM device

- qcom,usb-bam-num-pipes: max number of pipes that can be used

Optional properties:

- qcom,usb-bam-fifo-baseaddr: base address for bam pipe's data and descriptor

	fifos. This can be on chip memory (ocimem). This

	property is required if sub-node's mem-type is ocimem or usb private mem.

- qcom,disable-clk-gating: If present then disable BAM clock gating.

- qcom,usb-bam-override-threshold: If present then the default 512 byte threshold

	is overridden. This threshold configures the threshold value for Read/Write

	event generation by the BAM towards another BAM.

- qcom,usb-bam-max-mbps-highspeed: max mbps in high speed connection

	for either rx or tx direction.

- qcom,usb-bam-max-mbps-superspeed: max mbps in super speed connection

	for either rx or tx direction.

- qcom,reset-bam-on-connect: If present then BAM is RESET before connecting

	pipe. This may be required if BAM peripheral is also reset before connect.

- qcom,reset-bam-on-disconnect: If present then BAM is RESET after disconnecting pipes.

A number of USB BAM pipe parameters are represented as sub-nodes:

Subnode Required:

- label: a string describing uniquely the usb bam pipe. The string can be

	constracted as follows: <core>-<peer>-<direction>-<pipe num>.

	core options: hsusb, ssusb/dwc3, hsic

	peer options: qdss, ipa

	direction options: in (from peer to usb), out (from usb to peer)

	pipe num options: 0..127

- qcom,usb-bam-mem-type: Type of memory used by this PIPE. Can be one of

	0 - Uses SPS's dedicated pipe memory

	1 - System RAM allocated by driver

	2 - OCI memory residing @ 'qcom,usb-bam-fifo-baseaddr'

- qcom,dir: pipe direction

	0 - from usb (out)

	1 - to usb (in)

- qcom,pipe-num: pipe number

- qcom,peer-bam: peer BAM can be one of

	0 - QDSS_P_BAM

	1 - IPA_P_BAM

- qcom,data-fifo-size: data fifo size

- qcom,descriptor-fifo-size: descriptor fifo size

Optional Properties for Subnode:

- qcom,peer-bam-physical-address: peer BAM's physical address.

	Not specified for IPA and used only for qdss connection

- qcom,dst-bam-pipe-index: destination BAM pipe index

- qcom,src-bam-pipe-index: source BAM pipe index

- qcom,data-fifo-offset: data fifo offset address

- qcom,descriptor-fifo-offset: descriptor fifo offset address

- qcom,pipe-connection-type: type of pipe connection. Can be one of

	0 - BAM2BAM (default if not specified)

	1 - SYS2BAM (only supported on UL)

Example USB BAM controller device node:

	qcom,usbbam@f9a44000 {

		compatible = "qcom,usb-bam-msm";

		reg = <0xf9a44000 0x11000>;

		interrupts = <0 135 0>;

		qcom,usb-bam-num-pipes = <16>;

		qcom,ignore-core-reset-ack;

		qcom,disable-clk-gating;

		qcom,usb-bam-max-mbps-highspeed = <400>;

		qcom,usb-bam-max-mbps-superspeed = <3600>;

		qcom,bam-type = <1>;

		qcom,bam-mode = <0>;

		qcom,pipe0 {

			label = "hsusb-ipa-out-0";

			qcom,usb-bam-mem-type = <0>;

			qcom,dir = <0>;

			qcom,pipe-num = <0>;

			qcom,peer-bam = <2>;

			qcom,src-bam-pipe-index = <1>;

			qcom,data-fifo-offset = <0x2200>;

			qcom,data-fifo-size = <0x1e00>;

			qcom,descriptor-fifo-offset = <0x2100>;

			qcom,descriptor-fifo-size = <0x100>;

		};

		qcom,pipe1 {

			label = "hsusb-ipa-in-0";

			qcom,usb-bam-mem-type = <0>;

			qcom,dir = <1>;

			qcom,pipe-num = <0>;

			qcom,peer-bam = <2>;

			qcom,dst-bam-pipe-index = <0>;

			qcom,data-fifo-offset = <0x300>;

			qcom,data-fifo-size = <0x1e00>;

			qcom,descriptor-fifo-offset = <0>;

			qcom,descriptor-fifo-size = <0x300>;

		};

	};