1Here is the step-by-step to boot U-Boot on rv1108 evb.
2
3Get ddr init binary
4==============================================================================
5  > git clone  https://github.com/rockchip-linux/rkbin.git
6  > dd if=./rkbin/rv1x/rv1108ddr.bin of=ddr.bin bs=4 skip=1
7
8Compile  U-Boot
9===========================
10  > make CROSS_COMPILE=arm-linux-gnueabi- evb-rv1108_defconfig  all
11  > ./tools/mkimage  -n rv1108 -T rksd -d ddr.bin spl.bin
12  > cat spl.bin u-boot.bin > u-boot.img
13
14Flash the image by rkdeveloptool
15================================
16rkdeveloptool can get from https://github.com/rockchip-linux/rkdeveloptool.git
17
18Power on(or reset with RESET KEY) with MASKROM KEY preesed, and then:
19  > rkdeveloptool db ./rkbin/rv1x/RV1108_usb_boot.bin
20  > rkdeveloptool wl 0x40 u-boot.img
21  > rkdeveloptool RD
22
23You should be able to get U-Boot log message from boot console:
24
25DDR Version V1.02 20170220
26In
27400MHz
28DDR3
29Bus Width=16 Col=10 Bank=8 Row=15 CS=1 Die Bus-Width=16 Size=512MB
30mach:2
31OUT
32
33
34U-Boot 2017.05-00693-g3a5b171 (Jun 01 2017 - 17:37:53 +0800)
35
36Model: Rockchip RV1108 Evaluation board
37DRAM:  128 MiB
38APLL: 600000000 DPLL:792000000 GPLL:384000000
39MMC:
40Using default environment
41
42In:    serial@10210000
43Out:   serial@10210000
44Err:   serial@10210000
45Net:   No ethernet found.
46Hit any key to stop autoboot:  0
47=>
48