WinLink E850-96 board

Overview

WinLink’s E850-96 board [1] is based on Samsung Exynos850 SoC and follows 96Boards Consumer Edition specification [2]. That makes it possible to use 96Boards mezzanine boards [3] along with it. It’s an open-hardware board and the hardware design files [4] were published, along with the supported software [5] and related documentation.

U-Boot can be used on E850-96 instead of the original Samsung LittleKernel based bootloader [6]. Because FWBL1 [7] doesn’t verify bootloader’s signature, there is no need to sign a U-Boot binary. That means U-Boot binary can be flashed into bootloader partition (instead of LittleKernel bootloader) and it will just work.

Because BL2 bootloader already sets up DRAM and runs the final bootloader (U-Boot) from DRAM, there is no need in U-Boot SPL. It’s enough to have only U-Boot proper (u-boot.bin).

Boot Flow

The boot path for Exynos850 is shown on the figure below.

Legend:

• BL0: Boot ROM code

• BL1: Software part of Boot ROM

• EPBL: Exynos Primary Boot Loader

• BL2: Initializes CMU and DRAM and runs the final bootloader

• Bootloader: Final bootloader (e.g. U-Boot); also called BL33 in terms of ARM boot flow

• EL3_MON: EL3 monitor (trusted firmware, handles SMC calls); also called BL31 in terms of ARM boot flow

• LDFW: Loadable Firmware

Build Procedure

Warning

At the moment USB is not enabled in U-Boot for this board. Although eMMC is enabled, you won’t be able to flash images over USB (fastboot). So flashing U-Boot binary WILL effectively brick your board. The dltool [8] can be used then to perform USB boot and flash LittleKernel bootloader binary [7] to unbrick and revive the board. Flashing U-Boot binary might be helpful for developers or anybody who want to check current state of U-Boot enablement on E850-96 (which is mostly serial console, eMMC and related blocks).

Build U-Boot binary from source code (using AArch64 baremetal GCC toolchain):

export PATH=<toolchain path>/bin:$PATH
export CROSS_COMPILE=<toolchain prefix>
make e850-96_defconfig
make

Boot E850-96 board into fastboot mode as described in board software doc [9], and flash U-Boot binary into bootloader eMMC partition:

fastboot flash bootloader u-boot.bin
fastboot reboot

U-Boot will boot up to the shell.

References

[1]

https://www.96boards.org/product/e850-96b/

[2]

https://www.96boards.org/products/ce/

[3]

https://www.96boards.org/products/mezzanine/

[4]

https://www.96boards.org/documentation/consumer/e850-96b/hardware-docs/

[5]

https://gitlab.com/Linaro/96boards/e850-96/

[6]

https://gitlab.com/Linaro/96boards/e850-96/lk

[7] (1,2)

https://gitlab.com/Linaro/96boards/e850-96/images

[8]

https://gitlab.com/Linaro/96boards/e850-96/tools/dltool

[9]

https://gitlab.com/Linaro/96boards/e850-96/doc