CM-T3730: Android: Kernel
Contents
Overview
Linux kernel supplied with the CM-T3730 Android Demo package provides support for on-board peripherals and abstracts the functionality provided by the hardware. Current support coverage is specified at O/S support coverage map page. CompuLab provides ready-to-run binary kernel images, and source code of the modifications and additions made to the Linux kernel to work properly with CM-T3730 modules. The kernel binary is optimized for using with Android, however can be used with any Linux root filesystem as well.
Building kernel for CM-T3730
In this article we assume that the /home/development/cm-t3730/android directory is used for CM-T3730 kernel development.
Getting cross-compiler
The recommended pre-built toolchain repository is hosted on the Rowboat Gitorious website.
- Clone the toolchain repository. By default it will be created in the directory named prebuilts-gcc-linux-x86-arm-arm-eabi-4_6/.
cd /home/development/cm-t3730/android git clone -b rowboat-jb git://gitorious.org/rowboat/prebuilts-gcc-linux-x86-arm-arm-eabi-4_6.git
Getting kernel sources
The Rowboat Kernel sources repository is hosted on the Rowboat Gitorious website.
- Clone the kernel sources repository. By default it will be created in the directory named kernel/.
cd /home/development/cm-t3730/android git clone git://gitorious.org/rowboat/kernel.git
- Create a branch for CM-T3730 development. The CM-T3730 patches are generated vs. rowboat-jb-am37x-4.1.2 tag (c83d5f31dd92832fd83db48c073d82546c23eeab commit) in the Rowboat kernel tree. It is recommended to use exactly the same baseline to avoid merge conflicts:
git checkout -b cm-t3730-dev rowboat-jb-am37x-4.1.2
- Apply the CM-T3730 patch:
cd /home/development/cm-t3730/android/kernel git apply /path/to/cm-t3730-android/kernel/linux-2.6.37-cm-t3730-2.patch
Building the kernel
- Setup the toolchain
export PATH=/patch/to/cross/compiler/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6:$PATH export ARCH=arm export CROSS_COMPILE=arm-eabi-
- Build the kernel
cd /home/development/cm-t3730/android/kernel make cm_t3730_android_defconfig make menuconfig make uImage
In the example above, the Linux kernel image (uImage) will be created in /home/development/cm-t3730/android/kernel/arch/arm/boot directory.
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There is no need to build and install any kernel modules into the Android Demo image for CM-T3730, as all the kernel driver modules are compiled in the kernel binary. |
Basic platform support
The CM-T3730 basic platform support is implemented in the arch/arm/mach-omap2/board-cm-t35.c file of Linux kernel source tree. This file includes default setup of multi-functional pins, registration of the devices integrated in the CM-T3530/CM-T3730 modules and definitions of platform-specific configuration for these devices.
Audio
The CM-T3730 uses the audio module of the TPS65930 PMIC for analog audio input and output. The audio module is interfaced to the main processor through the TDM / I2S interface and used to transmit and receive audio data. The audio codec is connected via Multi-Channel Buffered Serial Port (McBSP) interface.
The CM-T3730 audio support is based on the Overo SoC Audio driver sound/soc/omap/overo.c.
To enable/disable it in the kernel configuration menu choose Device Drivers--->Sound card support--->Advanced Linux Sound Architecture--->ALSA for SoC audio support submenu.
Then enable/disable the SoC Audio support for Gumstix Overo and CompuLab CM-T35/CM-T3730.
┌───────────────────────── ALSA for SoC audio support ──────────────────────────┐ │ Arrow keys navigate the menu. <Enter> selects submenus --->. Highlighted │ │ letters are hotkeys. Pressing <Y> includes, <N> excludes, <M> modularizes │ │ features. Press <Esc><Esc> to exit, <?> for Help, </> for Search. Legend: │ │ [*] built-in [ ] excluded <M> module < > module capable │ │ ┌───────────────────────────────────────────────────────────────────────────┐ │ │ │ --- ALSA for SoC audio support │ │ │ │ <*> SoC Audio for the Texas Instruments OMAP chips │ │ │ │ <*> SoC Audio support for Gumstix Overo and CompuLab CM-T35/CM-T3730 │ │ │ │ < > Build all ASoC CODEC drivers │ │ │ │ <*> WL1271 Bluetooth Codec support │ │ │ │ │ │ │ └───────────────────────────────────────────────────────────────────────────┘ │ ├───────────────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └───────────────────────────────────────────────────────────────────────────────┘
Keypad
The matrix keypad is supplied with the CM-T3730 Evaluation Kit.
The default Linux Kernel keypad configuration is defined in the CM-T3530/CM-T3730 board file kernel/arch/arm/mach-omap2/board-cm-t35.c as follows:
static uint32_t cm_t35_keymap[] = {
KEY(0, 0, KEY_A), KEY(0, 1, KEY_B), KEY(0, 2, KEY_LEFT),
KEY(1, 0, KEY_UP), KEY(1, 1, KEY_ENTER), KEY(1, 2, KEY_DOWN),
KEY(2, 0, KEY_RIGHT), KEY(2, 1, KEY_C), KEY(2, 2, KEY_D),
};
The keypad is supported by the TWL4030 Keypad driver kernel/drivers/input/keyboard/twl4030_keypad.c. To enable/disable it in the kernel configuration menu choose Device Drivers--->Input device support--->Keyboards submenu. Then enable/disable the TI TWL4030/TWL5030/TPS659x0 keypad support .
┌────────────────────────────────── Keyboards ──────────────────────────────────┐ │ Arrow keys navigate the menu. <Enter> selects submenus --->. Highlighted │ │ letters are hotkeys. Pressing <Y> includes, <N> excludes, <M> modularizes │ │ features. Press <Esc><Esc> to exit, <?> for Help, </> for Search. Legend: │ │ [*] built-in [ ] excluded <M> module < > module capable │ │ ┌────^(-)───────────────────────────────────────────────────────────────────┐ │ │ │ < > Newton keyboard │ │ │ │ < > OpenCores Keyboard Controller │ │ │ │ < > Stowaway keyboard │ │ │ │ < > Sun Type 4 and Type 5 keyboard │ │ │ │ <*> TI TWL4030/TWL5030/TPS659x0 keypad support │ │ │ │ < > XT keyboard │ │ │ └───────────────────────────────────────────────────────────────────────────┘ │ ├───────────────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └───────────────────────────────────────────────────────────────────────────────┘
USB Gadget
The CM-T3730 Android Demo image supports both USB host and USB device ports.
USB host can be used to connect Keyboard/Mouse, Mass storage device, etc.
The USB device port is used for adb and USB accessory gadgets.
To enable/disable USB Gadget support in the kernel configuration menu choose Device Drivers--->USB support--->USB Gadget Support submenu.
Then enable/disable USB Gadget Drivers:
┌───────────────────────────── USB Gadget Support ──────────────────────────────┐ │ Arrow keys navigate the menu. <Enter> selects submenus --->. Highlighted │ │ letters are hotkeys. Pressing <Y> includes, <N> excludes, <M> modularizes │ │ features. Press <Esc><Esc> to exit, <?> for Help, </> for Search. Legend: │ │ [*] built-in [ ] excluded <M> module < > module capable │ │ ┌───────────────────────────────────────────────────────────────────────────┐ │ │ │ --- USB Gadget Support │ │ │ │ [ ] Debugging information files (DEVELOPMENT) │ │ │ │ [ ] Debugging information files in debugfs (DEVELOPMENT) │ │ │ │ (2) Maximum VBUS Power usage (2-500 mA) │ │ │ │ USB Peripheral Controller (Inventra HDRC USB Peripheral (TI, ADI,│ │ │ │ <*> USB Gadget Drivers (Android Gadget) ---> │ │ │ └───────────────────────────────────────────────────────────────────────────┘ │ ├───────────────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └───────────────────────────────────────────────────────────────────────────────┘
Finally choose Android Gadget option:
┌──────────────────────── USB Gadget Drivers ────────────────────────┐ │ Use the arrow keys to navigate this window or press the hotkey of │ │ the item you wish to select followed by the <SPACE BAR>. Press │ │ <?> for additional information about this option. │ │ ┌─────────^(-)───────────────────────────────────────────────────┐ │ │ │ ( ) File-backed Storage Gadget │ │ │ │ ( ) Mass Storage Gadget │ │ │ │ ( ) Serial Gadget (with CDC ACM and CDC OBEX support) │ │ │ │ ( ) MIDI Gadget (EXPERIMENTAL) │ │ │ │ ( ) Printer Gadget │ │ │ │ (X) Android Gadget │ │ │ └─────────v(+)───────────────────────────────────────────────────┘ │ ├────────────────────────────────────────────────────────────────────┤ │ <Select> < Help > │ └────────────────────────────────────────────────────────────────────┘
Wireless LAN
The CM-T3730 uses the TI WL1271 device. To enable/disable WLAN support in the kernel configuration menu choose Device Drivers--->Network device support submenu. Then enable/disable Wireless LAN:
┌─────────────────────────── Network device support ────────────────────────────┐ │ Arrow keys navigate the menu. <Enter> selects submenus --->. Highlighted │ │ letters are hotkeys. Pressing <Y> includes, <N> excludes, <M> modularizes │ │ features. Press <Esc><Esc> to exit, <?> for Help, </> for Search. Legend: │ │ [*] built-in [ ] excluded <M> module < > module capable │ │ ┌────^(-)───────────────────────────────────────────────────────────────────┐ │ │ │ [*] Ethernet (10000 Mbit) ---> │ │ │ │ [*] Wireless LAN ---> │ │ │ │ *** Enable WiMAX (Networking options) to see the WiMAX drivers **│ │ │ │ USB Network Adapters ---> │ │ │ │ [ ] Wan interfaces support ---> │ │ │ │ *** CAIF transport drivers *** │ │ │ └────v(+)───────────────────────────────────────────────────────────────────┘ │ ├───────────────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └───────────────────────────────────────────────────────────────────────────────┘
Additionally, in the kernel configuration menu choose Networking support--->Wireless submenu. Then enable/disable Wireless extensions sysfs files:
┌────────────────────────────────── Wireless ───────────────────────────────────┐ │ Arrow keys navigate the menu. <Enter> selects submenus --->. Highlighted │ │ letters are hotkeys. Pressing <Y> includes, <N> excludes, <M> modularizes │ │ features. Press <Esc><Esc> to exit, <?> for Help, </> for Search. Legend: │ │ [*] built-in [ ] excluded <M> module < > module capable │ │ ┌────^(-)───────────────────────────────────────────────────────────────────┐ │ │ │ [*] Wireless extensions sysfs files │ │ │ │ < > Common routines for IEEE802.11 drivers │ │ │ │ <M> Generic IEEE 802.11 Networking Stack (mac80211) │ │ │ │ [ ] PID controller based rate control algorithm │ │ │ │ [*] Minstrel │ │ │ │ [*] Minstrel 802.11n support │ │ │ └────v(+)───────────────────────────────────────────────────────────────────┘ │ ├───────────────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └───────────────────────────────────────────────────────────────────────────────┘
The relevant initialization including the pin-muxing for MMC bus is done in the CM-T3730 board file.
Please refer to the CM-T3530/CM-T3730 board file kernel/arch/arm/mach-omap2/board-cm-t35.c for more details.
