AM335X USB Driver User Guide 04.06.00
- 1 Quick Start Guide
- 2 Introduction
- 3 Linux Software Architecture
- 4 Driver Features
- 5 Configuration
- 6 Port mode configuration
- 7 Modular tests
- 8 USB OTG (HNP/SRP) testing
- 9 Software Interface
Quick Start Guide
This section is a quick guide on how to start using usb ports on AM335x platform with supplied pre-built binaries. Please refer to USB Quick Start
AM335x USB subsystem has two instance of mentor usb controller. Each controller is based on USB2.0 standards supporting high, full and low speed. Communication Port Programming Interface 4.1 (CPPI4.1) DMA controller is used by each musb controller to transfer data between external memory and endpoint FIFOs. There are 15 Tx and 15 Rx endpoints for each musb controller in addition to endpoint-0. CPPI4.1 DMA can not be used for data transfers on endpoint-0 and so CPU is used for all transfers on endpoint-0. Please refer to AM335x Technical Reference Manual (TRM) for details.
Acronyms & Definitions
|USB||Universal Serial Bus|
|OTG||On The Go|
|UAC||USB Audio Class|
|UVC||USB Video Class|
|HID||Human Interface Devices|
|CDC||Communication Device Class|
|RNDIS||Remote Network Device Interface Specification|
|DTM||Driver Test Manager|
Linux Software Architecture
MUSB controller driver
The Linux MUSB controller driver is a host controller driver (HCD) and gadget controller driver for musb controller. As musb controller is an OTG controller so each musb port can act as either as host or as a device. The musb host controller driver (HCD) registers the host controller hardware to linux usb core stack and similarly musb gadget controller driver registers itself to the udc core.
Linux USB Stack Architecture
Linux usb stack is a layered architecture where musb controller driver is at lowest layer. Linux USB core layer provides API interface to host class drivers and forwards the request from class drivers to intended host controller driver. Gadget drivers (function driver) binds itself with gadget controller driver and uses gadget drivers functions to perform data transfers.
This section describes the Linux musb controller driver feature.
- The musb controller driver can be built as loadable module or statically built inside the kernel image.
- Supports both PIO (non DMA mode) and DMA mode (Note: DMA mode not applicable for control endpoint)
- Concurrent usage of both the musb ports either in host or in device mode.
Please refer the table below for supported usb class and gadget drivers with the release.
|Hub class||Supported||File Storage Gadget||Supported|
|UVC||Supported from PSP-04.06.00.05 onward|
|UAC||Supported from PSP-04.06.00.05 onward|
|OTG (HNP)||Supported from PSP-04.06.00.05 onward|
This section describes the kernel config options to be selected for building musb controller driver along with host class and gadget drivers.
MUSB controller driver
Please refer MUSB Controller Driver Config for kernel config option for MUSB controller driver.
USB Host Configuration
This section has details of USB host class kernel configurations.
Host Mass Storage Class (MSC)
Please refer Host MSC for kernel config options to be enabled for host mass storage class.
Host HID class
Please refer Host HID for kernel config options to be enabled for host HID class.
Host Audio class
Please refer Host Audio for kernel config options to be enabled for host audio class.
Host Video class
Please refer Host Video for kernel config options to be enabled for host video class.
Host CDC class
Please refer Host CDC for kernel config options to be enabled for host CDC class.
USB Device Configuration
This section has details of USB gadget driver kernel configurations.
Device CDC and RNDIS gadget
Device File Storage gadget
Please refer File Storage Gadget for kernel config options to be enabled for File Storage gadget driver.
Module build for usb driver is supported. Please select <M> in place of <*> for all the drivers in kernel config as explained above.
Port mode configuration
AM335x has two musb port and each of them are OTG capable which means each of them can act host only or device only or both based on board configurations. Each musb port mode can be configured for a custom board at it's board file at arch/arm/mach-omap2/board-xxx.c. Please update "mode" field within 'struct omap_musb_board_data' for configuring port mode. mode[D0:D3] is mode for musb0 port and mode[D4:D7] is mode for musb1 port.
Selecting the musb controller driver as module would build four different module which needs to inserted in below order for testing musb port.
- insmod musb_hdrc.ko for inserting musb core module.
- insmod cppi41dma.ko for inserting dma module. Please skip this step if DMA is disabled.
- insmod ti81xx.ko for inserting platform glue module.
- insmod g_ether.ko OR insmod g_file_storage.ko file=<file-path> stall=0 to insert a gadget module. Please skip this step if port is configured to be host only in board file.
USB OTG (HNP/SRP) testing
Please refer USB OTG (HNP/SRP) testing for details on how to test HNP and SRP.