AM62x Beagleboard.org Beagleplay

Introduction:

BeagleBoard.org BeaglePlay is an easy to use, affordable open source hardware single board computer based on the Texas Instruments AM625 SoC that allows you to create connected devices that work even at long distances using IEEE 802.15.4g LR-WPAN and IEEE 802.3cg 10Base-T1L. Expansion is provided over open standards based mikroBUS, Grove and QWIIC headers among other interfaces.

Further information can be found at:

• Product Page: https://beagleplay.org/

• Hardware documentation: https://git.beagleboard.org/beagleplay/beagleplay

Boot Flow:

Below is the pictorial representation of boot flow:

• On this platform, ‘TI Foundational Security’ (TIFS) functions as the security enclave master while ‘Device Manager’ (DM), also known as the ‘TISCI server’ in "TI terminology", offers all the essential services. The A53 or M4F (Aux core) sends requests to TIFS/DM to accomplish these services, as illustrated in the diagram above.

Sources:

• Das U-Boot

  source: https://source.denx.de/u-boot/u-boot.git

  branch: master

• Trusted Firmware-A (TF-A)

  source: https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/

  branch: master

• Open Portable Trusted Execution Environment (OP-TEE)

  source: https://github.com/OP-TEE/optee_os.git

  branch: master

• TI Firmware (TIFS, DM, SYSFW)

  source: https://github.com/TexasInstruments/ti-linux-firmware

  branch: ti-linux-firmware

• TIFS - TI Foundational Security Firmware - Consists of purely firmware meant to run on the security enclave.

• DM - Device Management firmware also called TI System Control Interface server (TISCI Server) - This component purely plays the role of managing device resources such as power, clock, interrupts, dma etc. This firmware runs on a dedicated or multi-use microcontroller outside the security enclave.

• TIFS Stub - The TIFS stub is a small piece of binary designed to help restore the required security context and resume the TIFS firmware when the system resumes from low-power modes such as suspend-to-RAM/Deep Sleep. This stub uses the same encryption and customer key signing model as TIFS and is loaded into the ATCM (Tightly Coupled Memory ‘A’ of the DM R5) during DM startup. Due to the independent certificate signing process, the stub is maintained separately from DM.

Build procedure:

0. Setup the environment variables:

Set the variables corresponding to this platform:

exportCC32=arm-linux-gnueabihf-
exportCC64=aarch64-linux-gnu-
exportLNX_FW_PATH=path/to/ti-linux-firmware
exportTFA_PATH=path/to/trusted-firmware-a
exportOPTEE_PATH=path/to/optee_os

exportUBOOT_CFG_CORTEXR=am62x_beagleplay_r5_defconfig
exportUBOOT_CFG_CORTEXA=am62x_beagleplay_a53_defconfig
exportTFA_BOARD=lite
# we dont use any extra TFA parameters
unsetTFA_EXTRA_ARGS
exportOPTEE_PLATFORM=k3-am62x
exportOPTEE_EXTRA_ARGS="CFG_WITH_SOFTWARE_PRNG=y"

1. Trusted Firmware-A:

# inside trusted-firmware-a source
makeCROSS_COMPILE=$CC64ARCH=aarch64PLAT=k3SPD=opteed$TFA_EXTRA_ARGS\
TARGET_BOARD=$TFA_BOARD

2. OP-TEE:

# inside optee_os source
makeCROSS_COMPILE=$CC32CROSS_COMPILE64=$CC64CFG_ARM64_core=y$OPTEE_EXTRA_ARGS\
PLATFORM=$OPTEE_PLATFORM

3. U-Boot:

• 3.1 R5:

# inside u-boot source
make$UBOOT_CFG_CORTEXR
makeCROSS_COMPILE=$CC32BINMAN_INDIRS=$LNX_FW_PATH

• 3.1.1 Alternative build of R5 for DFU boot:

As the SPL size can get too big when building with support for booting both from local storage and DFU an extra config fragment should be used to enable DFU support (and disable storage support)

exportUBOOT_CFG_CORTEXR="${UBOOT_CFG_CORTEXR} am62x_r5_usbdfu.config"

# inside u-boot source
make$UBOOT_CFG_CORTEXR
makeCROSS_COMPILE=$CC32BINMAN_INDIRS=$LNX_FW_PATH

• 3.2 A53:

# inside u-boot source
make$UBOOT_CFG_CORTEXA
makeCROSS_COMPILE=$CC64BINMAN_INDIRS=$LNX_FW_PATH\
BL31=$TFA_PATH/build/k3/$TFA_BOARD/release/bl31.bin\
TEE=$OPTEE_PATH/out/arm-plat-k3/core/tee-raw.bin

• 3.2.1 Alternative build of A53 for Android bootflow:

Since the Android requires many more dependencies, it is disabled by default. An extra config fragment should be used to enable Android bootflow support.

exportUBOOT_CFG_CORTEXR="${UBOOT_CFG_CORTEXA} am62x_a53_android.config"

# inside u-boot source
make$UBOOT_CFG_CORTEXA
makeCROSS_COMPILE=$CC64BINMAN_INDIRS=$LNX_FW_PATH\
BL31=$TFA_PATH/build/k3/$TFA_BOARD/release/bl31.bin\
TEE=$OPTEE_PATH/out/arm-plat-k3/core/tee-raw.bin

Target Images

Copy these images to an SD card and boot:

• tiboot3.bin from Cortex-R5 build.

• tispl.bin and u-boot.img from Cortex-A build

Image formats

• tiboot3.bin

• tispl.bin

Additional hardware for U-Boot development

• Serial Console is critical for U-Boot development on BeaglePlay. See BeaglePlay serial console documentation.

• uSD is preferred option over eMMC, and a SD/MMC reader will be needed.

• (optionally) JTAG is useful when working with very early stages of boot.

Default storage options

There are multiple storage media options on BeaglePlay, but primarily:

• Onboard eMMC (default) - reliable, fast and meant for deployment use.

• SD/MMC card interface (hold ‘USR’ switch and power on) - Entirely depends on the SD card quality.

Flash to uSD card or how to deal with "bricked" Board

When deploying or working on Linux, it’s common to use the onboard eMMC. However, avoiding the eMMC and using the uSD card is safer when working with U-Boot.

If you choose to hand format your own bootable uSD card, be aware that it can be difficult. The following information may be helpful, but remember that it is only sometimes reliable, and partition options can cause issues. These can potentially help:

• https://git.ti.com/cgit/arago-project/tisdk-setup-scripts/tree/create-sdcard.sh

• https://elinux.org/Beagleboard:Expanding_File_System_Partition_On_A_microSD

The simplest option is to start with a standard distribution image like those in BeagleBoard.org Distros Page and download a disk image for BeaglePlay. Pick a 16GB+ uSD card to be on the safer side.

With an SD/MMC Card reader and Balena Etcher, having a functional setup in minutes is a trivial matter, and it works on almost all Host Operating Systems. Yes Windows users, Windows Subsystem for Linux(WSL) based development with U-Boot and update uSD card is practical.

Updating U-Boot is a matter of copying the tiboot3.bin, tispl.bin and u-boot.img to the "BOOT" partition of the uSD card. Remember to sync and unmount (or Eject - depending on the Operating System) the uSD card prior to physically removing from SD card reader.

Also see following section on switch setting used for booting using uSD card.

Flash to eMMC

The eMMC layout selected is user-friendly for developers. The boot hardware partition of the eMMC only contains the fixed-size tiboot3.bin image. This is because the contents of the boot partitions need to run from the SoC’s internal SRAM, which remains a fixed size constant. The other components of the boot sequence, such as tispl.bin and u-boot.img, are located in the /BOOT partition in the User Defined Area (UDA) hardware partition of the eMMC. These components can vary significantly in size. The choice of keeping tiboot3.bin in boot0 or boot1 partition depends on A/B update requirements.

The following are the steps from Linux shell to program eMMC:

# Enable Boot0 boot
mmcbootpartenable12/dev/mmcblk0
mmcbootbussetsingle_backwardx1x8/dev/mmcblk0
mmchwresetenable/dev/mmcblk0

# Clear eMMC boot0
echo'0'>>/sys/class/block/mmcblk0boot0/force_ro
ddif=/dev/zeroof=/dev/mmcblk0boot0count=32bs=128k
# Write tiboot3.bin
ddif=tiboot3.binof=/dev/mmcblk0boot0bs=128k

# Copy the rest of the boot binaries
mount/dev/mmcblk0p1/boot/firmware
cptispl.bin/boot/firmware
cpu-boot.img/boot/firmware
sync

LED patterns during boot

A53 SPL DDR Memory Layout

This provides an overview memory usage in A53 SPL stage.

Switch Setting for Boot Mode

The boot time option is configured via "USR" button on the board. See Beagleplay Schematics for details.

To switch to SD card boot mode, hold the USR button while powering on with a USB type C power supply, then release when power LED lights up.

DFU based boot

To boot the board over DFU, ensure there is no SD card inserted with a bootloader. Hold the USR switch while plugging into the type C to boot into DFU mode. After power-on the build artifacts needs to be uploaded one by one with a tool like dfu-util.

The initial ROM will have a DFU alt named bootloader for the initial R5 spl upload. The next stages as exposed by U-Boot have target alts matching the name of the artifacts, for these a USB reset has to be done after each upload.

When using dfu-util the following commands can be used to boot to a U-Boot shell:

dfu-util-abootloader-Dtiboot3.bin
dfu-util-R-atispl-Dtispl.bin
dfu-util-R-au-boot.img-Du-boot.img

Debugging U-Boot

See Common Debugging environment - OpenOCD: for detailed setup and debugging information.

Tag-Connect: Tag-Connect pads on the boards which require special cable. Please check the documentation to identify if "legged" or "no-leg" version of the cable is appropriate for the board.

To debug on these boards, you will need:

• TUMPA or equivalent dongles supported by OpenOCD.

• Tag-Connect cable appropriate to the board such as TC2050-IDC-NL

• In case of no-leg, version, a retaining clip

• Tag-Connect to ARM20 adapter

• External JTAG adapter/interface: In other cases, where an adapter/dongle is used, a simple cfg file can be created to integrate the SoC and adapter information. See supported TI K3 SoCs to decide if the SoC is supported or not.

openocd-fopenocd_connect.cfg

For example, with BeaglePlay (AM62X platform), the openocd_connect.cfg:

# TUMPA example:
# http://www.tiaowiki.com/w/TIAO_USB_Multi_Protocol_Adapter_User's_Manual
source[findinterface/ftdi/tumpa.cfg]
transportselectjtag
# default JTAG configuration has only SRST and no TRST
reset_configsrst_onlysrst_push_pull
# delay after SRST goes inactive
adaptersrstdelay20
if{![infoexistsSOC]}{
# Set the SoC of interest
setSOCam625
}
source[findtarget/ti_k3.cfg]
ftditdo_sample_edgefalling
# Speeds for FT2232H are in multiples of 2, and 32MHz is tops
# max speed we seem to achieve is ~20MHz.. so we pick 16MHz
adapterspeed16000