Skip to content

Device Tree overlays for sunxi devices running Armbian images with mainline kernel

License

Notifications You must be signed in to change notification settings

armbian/sunxi-DT-overlays

Folders and files

NameName
Last commit message
Last commit date

Latest commit

 

History

63 Commits
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Repository files navigation

Device Tree overlays for sunxi devices

Version

As of now overlays in this repository should work with the kernel version 4.14.x. They may need changes/adjustments to work on older versions and eventually they will be updated to newer kernel versions.

Technical info

Requirements
  • mainline u-boot 2017.03 or newer with CONFIG_OF_LIBFDT_OVERLAY enabled
  • latest version of appropriate boot script
  • existing armbianEnv.txt with correct overlay_prefix value
  • Device Tree compiler with overlays support for compiling the overlays

Notes:

  • Older u-boot versions require this patch to fix endiannes of values obtained with fdt get value command
Implementation details

Boot script reads /boot/armbianEnv.txt which may contain following environment variables:

  • overlay_prefix
  • overlays
  • user_overlays
  • overlay specific parameters

Overlay files referenced by overlays and user_overlays variables are loaded and applied using fdt apply command. After applying all overlays a SoC specific fixup script is executed to process overlay specific parameters.

Limitations
  • U-boot fdt command does not support "tuples" values which limits implementing things like GPIO SPI chip selects with variable GPIO pins that require this type of values:
cs-gpios = <0>, <&pio 0 1 0>, <&pio 7 7 0>; /* Native, PA1, PH7 */
  • U-boot does not support overlay parameters, so changing values is implemented via executing a "fixup" script after all overlays were applied. This script uses environment variables loaded from /boot/armbianEnv.txt to change the live tree using fdt command.

  • Since SoCs have multiple controllers of the same type (I2C, SPI) that can be exposed in different combinations on different boards, slave devices (I2C, I2S, SPI, ...) are provided not as ready to use overlays but as examples that require minimal editing to match the used configuration.

About

Device Tree overlays for sunxi devices running Armbian images with mainline kernel

Topics

Resources

License

Security policy

Stars

Watchers

Forks

Releases

No releases published

Packages

No packages published