U-Boot features

Following are some of the new features introduced in Variscite U-Boot 2015.04:

Splash Screen

A splash screen is enabled by default, and is shown on the LVDS LCD.
To disable the splash screen, stop the boot at u-boot command prompt and enter:

=> run disable_splash
=> saveenv

And to re-enable it:

=> run enable_splash
=> saveenv

The splash image is taken from /boot/splash.bmp in the root file system.
Note: It will take the splash image from whichever rootfs that is going to be mounted later at boot.

USB Mass Storage gadget

You can use the board as a USB Mass Storage device by connecting a USB cable between the OTG/Client port on the board and a host PC, and using U-Boot's ums command.
ums usage is:

ums <USB_controller> [<devtype>] <devnum>  e.g. ums 0 mmc 0
    devtype defaults to mmc

devtype can be any block device (e.g. mmc, usb)

To mount the eMMC (most useful):

If you are booting from eMMC on a DART-MX6 SOM:

=> ums 0 mmc 0

Otherwise:

=> ums 0 mmc 1

To mount an SD card:

If you are booting from eMMC on a DART-MX6 SOM:

=> ums 0 mmc 1

Otherwise:

=> ums 0 mmc 0

To mount a USB device connected to the USB Host port (least useful):

=> usb start
=> ums 0 usb 0

Once you've done that, the chosen block device will be mounted as a USB Mass Storage device on your PC and you can play with it however you like.
This is especially useful for updating the internal eMMC.
To exit the ums command press ctrl+c.
Note: You should use a Linux PC host as Windows can't naturally read ext file systems.

HDMI auto-detection

If an HDMI screen is connected to the board, it will auto-detect it on boot and use it as its display.
No need to manually change anything.
(What it actually does is automatically add "video=mxcfb0:dev=hdmi,1920x1080M@60,if=RGB24;" to the end of bootargs, if hdmi is detected).

USB mode on VAR-MX6CustomBoard

USB port 0 on VAR-MX6CustomBoard is not a fully native OTG - it supports either Client or Host mode.
When using it in U-Boot, it is set to Client mode by default and you can change it to Host mode by setting the following environment variable:

=> setenv usbmode host

You can change it back and forth in real time when using this USB port in U-Boot, but pay attention that you are using the USB port correctly, according to the mode you set it to.

Note: USB port 1 on VAR-MX6CustomBoard is always Host.

Choosing Root File System location when booting from NAND

If you're using a SOM with both NAND flash and eMMC, and you want to set the rootfs location to eMMC when booting from NAND, set the following environment variable:

=> setenv chosen_rootfs emmc

Otherwise, it will try to mount the rootfs from NAND.
(What it actually does is choose between the pre-defined bootargs_ubifs & bootargs_emmc).

Note: If you use our NAND/eMMC recovery SD card ver. 50 and above to flash Yocto, the chosen rootfs will be updated automatically to the location that you install the rootfs to - no need to manually change the environment.

DART-MX6 features previously missing

• U-Boot now supports both SD card and eMMC at the same time, also on DART-MX6 SOMs, regardless of where you boot from.
  

On DART-MX6 SOMs, the device you boot from is always mmc 0, and the other is mmc 1.

• U-Boot now supports USB also on DART-MX6 SOMs.