4.17. Rockchip RK3288

The RK3288 SoC has a two stage boot process. The booting is completed in two consecutive stages. The binary for the 1st stage is referred to as the Secondary Program Loader (SPL). The binary for the 2nd stage is simply referred to as barebox. SPL is a non-interactive loader and is only used to boot the 2nd stage loader.

At this moment barebox can only be used as a 2nd stage bootloader. Starting barebox requires another bootloader which will do the very basic SDRAM initialization for us. We can use the u-boot for that.

4.17.1. Building barebox

The RK3288 boards in barebox are covered by the rk3288_defconfig. The resulting images will be placed under images/:

::
barebox-rk3288-phycore-som.img

4.17.2. Starting and updating barebox

4.17.2.1. SD/MMC

For the first stage bootloader we will need an u-boot image. A detailed description on how to build and flash an RK3288 SPL image can be found in the u-boot source u-boot/doc/README.rockchip.

U-boot requires an image with a special header.

mkimage -A arm -T firmware -C none -O u-boot -a 0x02000000 -e 0 -n “barebox image” -d images/barebox-rk3288-phycore-som.img barebox.img

To write an image that boots from an SD card (assumed to be /dev/sdc):

sudo dd if=u-boot/u-boot-spl-dtb.bin of=/dev/sdc seek=64 bs=512 sudo dd if=barebox.img of=/dev/sdc seek=256 bs=512

This puts the Rockchip header and SPL image first and then places the barebox image at block 256 (i.e. 128KB from the start of the SD card). This corresponds with this setting in U-Boot:

#define CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR 256

4.17.3. RK3288 Boards