One of the shortcomings of the DragonBoard 410c was that it relied on the Android-phone-centric fastboot for any Kernel updates, but now there is a version of U-Boot available, thanks to Mateusz Kulikowski..

This is very much a work-in-progress, but I thought I would give it a try…

I started with the version at https://github.com/hallor/u-boot/tree/dragonboard-2015.11.01, and made some modifications to get it working on my 410c (Fedora 23, EXT4 rootfs, boot from SDCard)..

I should emphasize that I am a complete novice when it comes to hacking u-boot, and there may well be a better way of doing all this, but this worked, for me..

Modify u-boot/include/configs/dragonboard.h

add:
#define CONFIG_CMD_EXT4 /* EXT4 support */
#define CONFIG_SYS_BOOTM_LEN (16 << 20) /* Increase max image size */

And.. as the SAVEENV command was not included, for some reason – and I could not work out how to reenable it – I hard-coded the boot parameters, as follows:
after:
/* Environment – Boot*/
#define CONFIG_BOOTDELAY 5 /* autoboot after 5 seconds */
insert:
#define CONFIG_BOOTARGS “root=/dev/mmcblk1p1 rw rootwait console=tty0 console=ttyMSM0,115200n8 rootfs=ext4 noinitrd selinux=0”
#define CONFIG_BOOTCOMMAND “ext4load mmc 1:1 0x90000000 /boot/uImage; ext4load mmc 1:1 0x89000000 /boot/apq8016-sbc.dtb; bootm 0x90000000 – 0x89000000; ”
< each of these #defines should be a single line..>

Then:

#] make distclean
#] make dragonboard_config
#] make ARCH=arm CROSS_COMPILE=aarch64-linux-gnu-  (or whatever cross-compiler you are using..)

And make a ‘fake kernel’ image to use with fastboot, to install u-boot…

mkbootimg can be found at git://codeaurora.org/quic/kernel/skales, and I just installed it in /opt, and then added the location to the $PATH..

#] export PATH=/opt/skales:$PATH
#] mkbootimg --kernel=u-boot.bin --output=u-boot.img --dt=fake_dt --pagesize 2048 --base 0x80000000 --ramdisk=fake_ramdisk --cmdline=""
(su, and enable fastboot on the 410c, after connecting the USB cable, etc. etc..)
#] fastboot flash boot u-boot.img

So.. the fastboot-enabled ‘boot’ image is not the kernel now, but actually the u-boot executable.. You will only need to use fastboot to install/update u-boot.

The kernel can now be compiled on the Dragonboard, now, but the arm64 kernels do not include any built-in #make uImage or #make zImage capability, and so you will need to create a uImage after the #make Image kernel compile..

#] make defconfig (if necessary..)
#] make xconfig (select qcom...)
#] make -j5 Image
#] make dtbs
#] cp arch/arm64/boot/dts/qcom/apq8016-sbc.dtb /boot
#] make -j5 modules
#] make modules_install
#] make firmware_install
#] cp System.map /boot
#] cp arch/arm64/boot/Image /boot

Then in the /boot directory:

#] mkimage -A arm64 -O linux -C none -T kernel -a 0x80080000 -e 0x80080000 -n Dragonboard -d Image uImage

U-boot boot sequence – after u-boot is loaded by the old android bootloader:

U-Boot 2015.10-00449-g8e0b5c4-dirty (Nov 09 2015 - 14:13:46 -0800)
Qualcomm-DragonBoard 410C

DRAM: 986 MiB
MMC: msm_sdhci: 0, msm_sdhci: 1
Using default environment

In: serial
Out: serial
Err: serial
Net: Net Initialization Skipped
No ethernet found.
Hit any key to stop autoboot: 0
=> printenv
baudrate=115200
bootargs=root=/dev/mmcblk1p1 rw rootwait console=tty0 console=ttyMSM0,115200n8 rootfs=ext4 noinitrd selinux=0
bootcmd=ext4load mmc 1:1 0x90000000 /boot/uImage; ext4load mmc 1:1 0x89000000 /boot/apq8016-sbc.dtb; bootm 0x90000000 - 0x89000000;
bootdelay=5
stderr=serial
stdin=serial
stdout=serial

Environment size: 327/4092 bytes
=> boot

<< Linux Kernel boots… >>

.................
[ OK ] Reached target Network is Online.
 Starting LSB: Start or stop the Webmin server...
 Starting rolekit - role server...
 Starting Availability of block devices...
[ OK ] Reached target Remote File Systems (Pre).
[ OK ] Reached target Remote File Systems.
 Starting Permit User Sessions...
[ OK ] Started OpenSSH server daemon.
 Starting OpenSSH server daemon...
[ OK ] Started Availability of block devices.
[ OK ] Started Permit User Sessions.
 Starting Terminate Plymouth Boot Screen...
[ OK ] Started Command Scheduler.
 Starting Command Scheduler...
 Starting Wait for Plymouth Boot Screen to Quit...

Fedora 23 (Twenty Three)
Kernel 4.2.0 on an aarch64 (ttyMSM0)

rg410c login:

So.. I now have a Dragonboard 410c that I can compile the kernel on, and boot, without having to cross-compile or connect USB cables!

Robert Gadsdon.   November 9, 2015.
Updated November 12, to add info on mkbootimg..