1Here is the step-by-step to boot to U-Boot on RK3368-uQ7
2
3Get the Source and build ATF
4============================
5
6  > git clone git://git.theobroma-systems.com/arm-trusted-firmware.git
7  > cd arm-trusted-firmware
8  > make CROSS_COMPILE=aarch64-linux-gnu- PLAT=rk3368 bl31
9  > cp build/rk3368/release/bl31.bin ../u-boot/bl31-rk3368.bin
10
11Configure U-Boot
12================
13
14  > cd ../u-boot
15  > make lion-rk3368_defconfig
16
17Build the TPL/SPL stage
18=======================
19
20  > make CROSS_COMPILE=aarch64-unknown-elf- ARCH=arm
21  > tools/mkimage -n rk3368 -T rksd -d tpl/u-boot-tpl.bin spl-3368.img
22  > cat spl/u-boot-spl-dtb.bin >> spl-3368.img
23
24Build the full U-Boot and a FIT image including the ATF
25=======================================================
26
27  > make CROSS_COMPILE=aarch64-unknown-elf- ARCH=arm u-boot.itb
28
29Write to a SD-card
30==================
31
32  > dd if=spl-3368.img of=/dev/sdb seek=64
33  > dd if=u-boot.itb of=/dev/sdb seek=512
34
35
36If everything went according to plan, you should see the following
37output on UART0:
38
39<debug_uart> U-Boot TPL board init
40Trying to boot from BOOTROM
41Returning to boot ROM...
42Trying to boot from MMC1
43NOTICE:  BL31: v1.3(release):v1.2-1320-gbf43a443
44NOTICE:  BL31: Built : 18:04:47, Jul  5 2017
45
46
47U-Boot 2017.07-00158-g2395e99858 (Jul 18 2017 - 21:03:31 +0200)
48
49Model: Theobroma Systems RK3368-uQ7 SoM
50DRAM:  2 GiB
51MMC:   dwmmc@ff0c0000: 1, dwmmc@ff0f0000: 0
52Using default environment
53
54In:    serial@ff180000
55Out:   serial@ff180000
56Err:   serial@ff180000
57Net:
58Warning: ethernet@ff290000 (eth0) using random MAC address - d2:69:35:7e:d0:1e
59eth0: ethernet@ff290000
60Hit any key to stop autoboot:  2
61