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Uboot_201603

U-Boot​

This platform includes U-Boot as the bootloader to load and boot the full operating system. The i.MX6UL processor loads U-Boot from the eMMC flash at power-on. U-Boot allows booting images from the microSD, eMMC, NFS, or USB. U-Boot is a general purpose bootloader that is capable of booting into common Linux distributions, Android, QNX, or others.

Most users will not need to customize u-boot further, and can skip this section.

On a normal boot, output from U-Boot will be similar to the following:

    U-Boot 2016.03-00305-g75344a5 (Dec 15 2017 - 13:53:14 -0800)

    CPU:   Freescale i.MX6UL rev1.1 at 396 MHz
    Reset cause: WDOG
    Board: Technologic Systems TS-7553-V2
    I2C:   ready
    DRAM:  512 MiB
    MMC:   FSL_SDHC: 0, FSL_SDHC: 1
    Net:   FEC0 [PRIME]
    Booting from the SD card ...
    ** File not found /boot/boot.ub **
    34511 bytes read in 162 ms (208 KiB/s)
    5460520 bytes read in 391 ms (13.3 MiB/s)
    NO CHRG jumper is set, not waiting
    Kernel image @ 0x80800000 [ 0x000000 - 0x535228 ]
    ## Flattened Device Tree blob at 83000000
       Booting using the fdt blob at 0x83000000
       Using Device Tree in place at 83000000, end 8300b6ce

    Starting kernel ...

Modify Linux Kernel cmdline​

The Linux kernel cmdline can be customized by modifying the cmdline_append variable. If new arguments are added, the existing value should also be included with the new arguments.

env set cmdline_append rw rootwait console=ttymxc0,115200 quiet
env save

The kernel command line can also be modified from from the onboard Linux. From the linux shell prompt run the following commands to install the necessary tools and create the script:

apt-get update && apt-get install u-boot-tools -y
echo "env set cmdline_append rw rootwait console=ttymxc0,115200 quiet" > /boot/boot.scr
mkimage -A arm -T script -C none -n 'tsimx6ul boot script' -d /boot/boot.scr /boot/boot.ub

The boot.scr includes the plain text commands to be run in U-Boot on startup. The mkimage tool adds a checksum and header to this file which can be loaded by U-Boot. The .ub file should not be edited directly.

Booting From NFS​

U-Boot's NFS support can be used to load a kernel, device tree binary, and root filesystem. The default scripts include an example NFS boot script. Because of the way U-Boot tries to infer server data, the script we use will bypass this, making it more straightforward to use an NFS root that will not be heavily dependent on a particular network configuration.

# Set this to your NFS server IP and NFS directory path
env set serverip 192.168.0.1 
env set nfsroot ${serverip}:/path/to/nfs/rootfs/
env save

To boot your NFS root:

# Boot to NFS once
run nfsboot;

# To make the NFS boot the persistent default
env set bootcmd run nfsboot;
env save
warning

If bootcmd is used to test for whether the system should stop at the U-Boot shell or continue, the above will make it difficult to get back to the U-Boot shell as it will always attempt to boot regardless of jumper status.

USB Boot​

By default, U-Boot will attempt to read a U-Boot script from a USB drive when the U-Boot jumper is set (or the reset button is enabled and depressed). It copies /tsinit.ub into memory and jumps in to the script.

The one addition is to create the tsinit.ub file in the root of the USB drive. In order to do this, a U-Boot script must be created and then converted to the .ub format. This process requires a set of U-Boot specific tools. These are available on most every linux distribution, the instructions below are for Debian, either run on a host PC or on the device itself. See the package installation documentation for other respective distributions.

Install U-Boot tools in Debian​

apt-get update && apt-get install u-boot-tools -y

To make a bootable drive, create a single ext4 partition on a USB drive and unpack the rootfs tarball located here.

The one addition is to create the tsinit.ub file in the root of the USB drive. In order to do this, a U-Boot script must be created and then converted to the .ub format. This process requires a set of U-Boot specific tools.

These are available on most every linux distribution, either run on a host PC or on the device itself. See the package installation documentation.

Create the file tsinit.scr in the root of the USB drive with the linux filesystem:

# Prepare with:
# mkimage -A arm -T script -C none -n 'ts7553v2 usb' -d tsinit.scr tsinit.ub

# DO NOT MANUALLY EDIT THE .UB FILE

load usb 0:1 ${fdtaddr} /boot/imx6ul-ts7553v2${variant}.dtb;

load usb 0:1 ${loadaddr} /boot/zImage;

setenv bootargs root=/dev/sda1 ${cmdline_append};
bootz ${loadaddr} - ${fdtaddr};

Then in the same directory generate the tsinit.ub file:

mkimage -A arm -T script -C none -n 'ts7553v2 usb' -d tsinit.scr tsinit.ub

Update U-Boot​

danger

Installing a custom U-Boot is not recommended and may cause the device to fail to boot.

The latest U-Boot binary can be downloaded from the FTP site. Copy this file to /boot/u-boot.imx on the 1st partition of the SD card.

The U-Boot binary can be updated by inserting that SD card in to the board, setting the U-Boot and SD card jumpers, and powering up the unit. At the U-Boot prompt, the following command can be used:

run update-uboot

The above script will use the /boot/u-boot.imx file from the SD card or eMMC, depending on the state of the SD Boot jumper.

U-Boot Development​

We do provide our U-Boot sources, but we do not recommend rebuilding a custom U-Boot binary as it can leave the system in an unbootable state.

If you still want to proceed with building a custom U-Boot, use the tsimx_v2016.03_4.1.15_2.0.0_ga branch from the github here: https://github.com/embeddedTS/u-boot-imx

When compiling, we recommend using ONLY this cross-compiler: https://files.embeddedts.com/ts-arm-sbc/ts-7553-V2-linux/cross-toolchains/tsimx6ul-glibc-gnueabihf-4.9.4.tar.xz.

Specifically, we have experienced RAM problems when using a more recent cross compiler to build this version of U-Boot. The use of any other compiler may leave the system in an unbootable state!

This will output a u-boot.imx that can be written to the device using the steps in Update U-Boot.

export ARCH=arm
export CROSS_COMPILE=/path/to/folder/bin/arm-tsimx6ul-linux-gnueabihf-

make ts7553v2_defconfig
make u-boot.imx

POST​

The board includes a simple POST test. This is normally used in production to verify basic functionality rapidly before doing more thorough testing. By default, this is not enabled on every boot, but it can be added via U-Boot scripting if there is a need for additional confidence in the application. The POST test quickly verifies basic functionality of: USB, RTC, Ethernet PHY, FRAM (if present), WiFi/BT module (if present), eMMC (see warning below), RAM, and the supervisory microcontroller.

The post test can be run with the following command in U-Boot:

post
danger

The post command has an optional -d argument

When this argument is passed it does a write and read back test of the eMMC and FRAM which is DESTRUCTIVE to the data on the disk! Note that it will not modify the boot sector contents of the eMMC. The eMMC chip is still tested for basic functionality without the argument passed, but no data is read or written from the disk itself.