CM-T335: Linux: Kernel
Contents
Overview
Linux kernel for the CompuLab CM-T335 System-on-Module / Computer-on-Module 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-T335 modules.
Kernel command line
The Linux kernel for CM-T335 is shipped with built-in command line parameters:
console=ttyO0,115200n8 root=ubi0:rootfs rw rootfstype=ubifs ubi.mtd=rootfs
The default kernel command line defines primary console and root device.
Setting U-Boot bootargs environment variable overrides default kernel command line and can be used to set desired kernel parameters.
Select video output
Default CM-T335 video output device is DVI. Other video output devices can be used as well.
- LCD video output can be enabled by adding the following boot options to the kernel command line parameters:
cm_t335_disp=lcd
- LVDS video output can be enabled by adding the following boot options to the kernel command line parameters:
cm_t335_disp=lvds
Building kernel for CM-T335
Cross-Compiler
There are several options for cross-compilation toolchain setup. You can either compile your cross-compiler or use an already built cross-compiler. The cross-compiler should support the ARM embedded-application binary interface ("EABI")
- Pre-built toolchain (recommended):
- Tools for creating cross-compilers:
- Crosstool-ng: Builds a cross-compiler from source. Non-distribution specific.
- Crossdev: Gentoo's cross-compiler builder. Needs Gentoo.
U-Boot mkimage tool
U-Boot mkimage utility is required in order to create kernel images that can be loaded by the CM-T335 bootloader. You can download prebuilt mkimage binary or build it yourself:
mkdir ~/tmp
cd tmp
wget ftp://ftp.denx.de/pub/u-boot/u-boot-latest.tar.bz2
tar -xjvf u-boot-latest.tar.bz2
cd u-boot-20xx.xx
touch include/config.{h,mk}
make tools
sudo install tools/mkimage /usr/local/bin
Getting kernel sources
There are two ways to get Linux kernel sources that can be used as a baseline for CM-T335 kernel. You can create a copy of Linux Integration/Staging git tree for AM33x SoC maintained by Arago Project or download a snapshot and extract it. We assume that you have created /home/development/cm-t335/kernel directory for CM-T335 kernel development.
Snapshot download
- Download v3.2-staging snapshot with your web browser.
- Extract the downloaded archive linux-am33x-refs_heads_v3.2-staging.tar.gz
cd /home/development/cm-t335/kernel tar xvf /path/to/downloaded/linux-am33x-refs_heads_v3.2-staging.tar.gz mv linux-am33x linux-cm-t335
- This will create /home/development/cm-t335/kernel/linux-cm-t335 directory containing linux kernel tree.
- Apply the CM-T335 patch
cd /home/development/cm-t335/kernel/linux-cm-t335 patch -p1 < /path/to/cm-t335-linux/kernel/linux-3.2.0-cm-t335-4.4.patch
Git clone
- Install git version control system.
- Create a clone of linux kernel tree
cd /home/development/cm-t335/kernel git clone git://arago-project.org/git/projects/linux-am33x.git linux-cm-t335
- Create a branch for CM-T335 development. The CM-T335 patches are generated vs. b81bf04091986fa3893f31955564594567be3b61 commit in the Linux tree. It is recommended to use exactly the same baseline to avoid merge conflicts.
git checkout -b cm-t335-dev b81bf04091986fa3893f31955564594567be3b61
- Apply the CM-T335 patch
cd /home/development/cm-t335/kernel/linux-cm-t335 git apply /path/to/cm-t335-linux/kernel/linux-3.2.0-cm-t335-4.4.patch
Getting Power Management Firmware
- Download the firmware from Texas Instruments AM335x PSP
- Copy the firmware to the kernel source tree
cp /path/to/downloaded/bin-am335x-pm-firmware.bin /home/development/cm-t335/kernel/linux-cm-t335/firmware/am335x-pm-firmware.bin
Building the kernel
export ARCH=arm
export CROSS_COMPILE=arm-none-linux-eabi-
make cm_t335_defconfig
make menuconfig
make && make uImage && \
INSTALL_MOD_PATH=/home/development/cm-t335/rootfs make modules_install
In the example above, the Linux kernel image (uImage) will be created in /home/development/cm-t335/kernel/linux-cm-t335/arch/arm/boot, and the loadable kernel modules will be installed into the /home/development/cm-t335/rootfs/lib/modules directory.
When the CM-T335 is booted with the kernel image created as described above and with networked root filesystem at /home/development/cm-t335/rootfs/, the system will be able to load the kernel modules properly, thus avoiding module version problems.
Basic platform support
Analog Audio Support
In the kernel configuration menu choose Device Drivers ---> Sound card support ---> Advanced Linux Sound Architecture ---> ALSA for SoC audio support submenu and enable:
- SoC Audio for the AM33XX chip
- SoC Audio support for Compulab CM-T335
┌──────────────── 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: │ │ ┌─────────────────────────────────────────────────────────┐ │ │ │ --- ALSA for SoC audio support │ │ │ │ [ ] Support LZO compression for register caches │ │ │ │ <*> SoC Audio for the AM33XX chip │ │ │ │ < > SoC Audio support for AM335X EVM │ │ │ │ <*> SoC Audio support for Compulab CM-T335 │ │ │ │ < > SoC Audio for the Texas Instruments OMAP chips │ │ │ │ < > Build all ASoC CODEC drivers │ │ │ └─────────────────────────────────────────────────────────┘ │ ├─────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └─────────────────────────────────────────────────────────────┘
Controller–area network (CAN) support
-
The CM-T335 features a TI DCAN Controller Area Network (DCAN), integrated into the Sitara AM335X SoC.
The TI DCAN module supports bitrates up to 1 Mbit/s and is compliant to the CAN 2.0B protocol specification.
In the kernel configuration menu choose Networking support submenu and enable:
- CAN bus subsystem support
┌───────────────────── CAN bus subsystem 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 │ │ ┌─────────────────────────────────────────────────────────────────┐ │ │ │ [ ] Amateur Radio support ---> │ │ │ │ <*> CAN bus subsystem support ---> │ │ │ │ < > IrDA (infrared) subsystem support ---> │ │ │ └─────────────────────────────────────────────────────────────────┘ │ ├─────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └─────────────────────────────────────────────────────────────────────┘
In the kernel configuration menu choose Networking support ---> CAN bus subsystem support submenu and enable CAN protocol support:
- Raw CAN Protocol
- Broadcast Manager CAN Protocol
You can choose to either build it into the kernel or to compile it as a module named can-raw and can-bcm respectively.
┌───────────────────── CAN bus subsystem 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 │ │ ┌─────────────────────────────────────────────────────────────────┐ │ │ │ --- CAN bus subsystem support │ │ │ │ <*> Raw CAN Protocol (raw access with CAN-ID filtering) │ │ │ │ <*> Broadcast Manager CAN Protocol (with content filtering)│ │ │ │ < > CAN Gateway/Router (with netlink configuration) │ │ │ │ CAN Device Drivers ---> │ │ │ └─────────────────────────────────────────────────────────────────┘ │ ├─────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └─────────────────────────────────────────────────────────────────────┘
Next, in the kernel configuration menu choose Networking support ---> CAN bus subsystem support ---> CAN Device Drivers submenu and enable following options:
- Platform CAN drivers with Netlink support (built into the kernel or as a module named can-dev)
- CAN bit-timing calculation
- Bosch D_CAN devices (built into the kernel or as a module named d_can)
┌──────────────────────── CAN Device Drivers ─────────────────────────┐ │ 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 │ │ ┌─────────────────────────────────────────────────────────────────┐ │ │ │ < > Virtual Local CAN Interface (vcan) │ │ │ │ < > Serial / USB serial CAN Adaptors (slcan) │ │ │ │ <*> Platform CAN drivers with Netlink support │ │ │ │ [*] CAN bit-timing calculation │ │ │ │ < > TI High End CAN Controller │ │ │ │ < > Microchip MCP251x SPI CAN controllers │ │ │ │ < > Philips/NXP SJA1000 devices ---> │ │ │ │ < > Bosch C_CAN devices ---> │ │ │ │ <*> Bosch D_CAN devices ---> │ │ │ │ CAN USB interfaces ---> │ │ │ └────v(+)─────────────────────────────────────────────────────────┘ │ ├─────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └─────────────────────────────────────────────────────────────────────┘
Finally, in the kernel configuration menu choose Networking support ---> CAN bus subsystem support ---> CAN Device Drivers ---> Bosch D_CAN devices submenu and enable:
- Generic Platform Bus based D_CAN driver (built into the kernel or as a module named d_can_platform).
┌──────────────────────── Bosch D_CAN devices ────────────────────────┐ │ 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 │ │ ┌─────────────────────────────────────────────────────────────────┐ │ │ │ --- Bosch D_CAN devices │ │ │ │ <M> Generic Platform Bus based D_CAN driver │ │ │ └─────────────────────────────────────────────────────────────────┘ │ ├─────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └─────────────────────────────────────────────────────────────────────┘
Touchscreen Support
In the kernel configuration menu choose Device Drivers ---> Input device support submenu and enable:
- Touchscreens
┌─────────────────────── Input 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 │ │ ┌────^(-)─────────────────────────────────────────────────────────┐ │ │ │ [ ] Joysticks/Gamepads ---> │ │ │ │ [ ] Tablets ---> │ │ │ │ [*] Touchscreens ---> │ │ │ │ [*] Miscellaneous devices ---> │ │ │ │ Hardware I/O ports ---> │ │ │ └─────────────────────────────────────────────────────────────────┘ │ ├─────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └─────────────────────────────────────────────────────────────────────┘
Next, in the kernel configuration menu choose Device Drivers ---> Input device support ---> Touchscreens submenu and enable:
- TI Touchscreen Interface
┌───────────────────────────── Touchscreens ──────────────────────────┐ │ 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 │ │ ┌────^(-)─────────────────────────────────────────────────────────┐ │ │ │ < > Touchright serial touchscreen │ │ │ │ < > Touchwin serial touchscreen │ │ │ │ <*> TI Touchscreen Interface │ │ │ │ < > USB Touchscreen Driver │ │ │ │ < > Sahara TouchIT-213 touchscreen │ │ │ └────v(+)─────────────────────────────────────────────────────────┘ │ ├─────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └─────────────────────────────────────────────────────────────────────┘
Finally, in the kernel configuration menu choose Device Drivers ---> Multifunction device drivers submenu and enable
- TI ADC / Touch Screen chip support
┌─────────────────── Multifunction device drivers ────────────────────┐ │ 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 │ │ ┌─────────────────────────────────────────────────────────────────┐ │ │ │ < > TPS6507x Power Management / Touch Screen chips │ │ │ │ <*> TI ADC / Touch Screen chip support │ │ │ │ < > TPS65217 Power Management / White LED chips │ │ │ │ [ ] TPS6586x Power Management chips │ │ │ └────v(+)─────────────────────────────────────────────────────────┘ │ ├─────────────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └─────────────────────────────────────────────────────────────────────┘
WLAN and Bluetooth
-
CM-T335 has WLAN and Bluetooth support based on TI WL1271.
WLAN
In the kernel configuration menu choose Networking support ---> Wireless submenu and enable following options:
- cfg80211
- Common routines for IEEE802.11 drivers
- mac80211
┌────────────────────────── 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: │ │ ┌───────────────────────────────────────────────────────────┐ │ │ │ --- Wireless │ │ │ │ <M> cfg80211 - wireless configuration API │ │ │ │ [ ] nl80211 testmode command │ │ │ │ [ ] enable developer warnings │ │ │ │ [ ] cfg80211 regulatory debugging │ │ │ │ [*] enable powersave by default │ │ │ │ [ ] cfg80211 DebugFS entries │ │ │ │ [*] cfg80211 wireless extensions compatibility │ │ │ │ [*] Wireless extensions sysfs files │ │ │ │ <M> Common routines for IEEE802.11 drivers │ │ │ │ [ ] lib80211 debugging messages │ │ │ │ <M> Generic IEEE 802.11 Networking Stack (mac80211) │ │ │ │ Default rate control algorithm (Minstrel) ---> │ │ │ └────v(+)───────────────────────────────────────────────────┘ │ ├───────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └───────────────────────────────────────────────────────────────┘
Next, in the kernel configuration menu choose Device Drivers ---> Network device support ---> Wireless LAN submenu and enable:
- TI wl12xx driver support
┌──────────────────────── Wireless LAN ─────────────────────────┐ │ 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: │ │ ┌────^(-)───────────────────────────────────────────────────┐ │ │ │ < > Realtek RTL8192CU/RTL8188CU USB Wireless Network │ │ │ │ < > TI wl1251 driver support ---> │ │ │ │ <M> TI wl12xx driver support ---> │ │ │ │ < > ZyDAS ZD1211/ZD1211B USB-wireless support │ │ │ └───────────────────────────────────────────────────────────┘ │ ├───────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └───────────────────────────────────────────────────────────────┘
Finally, in the kernel configuration menu Device Drivers ---> Network device support ---> Wireless LAN ---> TI wl12xx driver support submenu enable:
- TI wl12xx support
- TI wl12xx SPI support
┌────────────────── TI wl12xx driver 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: │ │ ┌───────────────────────────────────────────────────────────┐ │ │ │ --- TI wl12xx driver support │ │ │ │ <M> TI wl12xx support │ │ │ │ <M> TI wl12xx SPI support │ │ │ │ < > TI wl12xx SDIO support │ │ │ └───────────────────────────────────────────────────────────┘ │ ├───────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └───────────────────────────────────────────────────────────────┘
Bluetooth
In the kernel configuration menu choose Networking support ---> Bluetooth subsystem support submenu and enable following options:
┌───────────────── Bluetooth subsystem 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: │ │ ┌───────────────────────────────────────────────────────────┐ │ │ │ --- Bluetooth subsystem support │ │ │ │ [*] L2CAP protocol support │ │ │ │ [*] SCO links support │ │ │ │ <M> RFCOMM protocol support │ │ │ │ [*] RFCOMM TTY support │ │ │ │ <M> BNEP protocol support │ │ │ │ [*] Multicast filter support │ │ │ │ [*] Protocol filter support │ │ │ │ <M> HIDP protocol support │ │ │ │ Bluetooth device drivers ---> │ │ │ └───────────────────────────────────────────────────────────┘ │ ├───────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └───────────────────────────────────────────────────────────────┘
Next, in the kernel configuration menu choose Networking support ---> Bluetooth subsystem support ---> Bluetooth device drivers submenu and enable following options:
┌────────────────── Bluetooth device drivers ───────────────────┐ │ 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: │ │ ┌───────────────────────────────────────────────────────────┐ │ │ │ < > HCI USB driver │ │ │ │ < > HCI SDIO driver │ │ │ │ <M> HCI UART driver │ │ │ │ [*] UART (H4) protocol support │ │ │ │ [*] BCSP protocol support │ │ │ │ [ ] Atheros AR300x serial support │ │ │ │ [*] HCILL protocol support │ │ │ │ < > HCI BCM203x USB driver │ │ │ │ < > HCI BPA10x USB driver │ │ │ │ < > HCI BlueFRITZ! USB driver │ │ │ └────v(+)───────────────────────────────────────────────────┘ │ ├───────────────────────────────────────────────────────────────┤ │ <Select> < Exit > < Help > │ └───────────────────────────────────────────────────────────────┘
