Configuring the Bootloader

The bootloader, one of the key software components included in the BSP, completes the required hardware initialization to download and run operating system images. The boot mode is selected from the S5 dipswitch on the carrier board and determines where the hardware looks for the primary bootloader.

Boot Options

The target can be booted from eMMC or SD Card. In our standard configuration, the kernel and root filesystem are loaded from SD/MMC.

The boot options for the kernel and root filesystem can be changed from within U-Boot. To enter U-Boot, after application of power, approximately three seconds are allotted for the user to hit any key which will halt autoboot of Linux:

../_images/pcm-067_bootconfig-uboot_console.png

Tip

help will show you the commands available to you in U-Boot and their usage.

Stand-Alone eMMC Boot

To configure U-Boot to boot the kernel from eMMC, modify the mmcdev and bootpart environment variables in U-Boot and save the environment:

Target (U-Boot)

  setenv mmcdev 0
  setenv bootpart 0:1
  saveenv

Stand-Alone SD/MMC Card Boot

By default, the phyCORE-AM65x Development Kit is set up to boot the Linux kernel and root filesystem from SD. If switching from another boot configuration back to SD, modify the mmcdev and bootpart environment variables in U-Boot and save the environment:

Target (U-Boot)

setenv mmcdev 1
setenv bootpart 1:2
saveenv

Custom Boot

Unique boot configurations can be created by defining the desired environment variable settings and setting bootcmd to run its contents.