Dragonboard410c

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Warning
This is work in progress and incomplete. Don't expect to get something working out of following these instructions yet.

The Dragonboard410c is a credit-card sized minicomputer, akin to the popular RaspberryPi series. It's sporting a Qualcomm Snapdragon 410, quad-core Cortex A53 @ 1.2GHz (which implies 64bit arch) and an Adreno 306 GPU.

Hardware

Standard

Device Make/model Status Kernel driver(s) Kernel version Notes
CPU ARM Cortex A53 @ 1.2GHz Works N/A N/A quad-core, 64bit
Graphics Adreno 306 GPU @ 400MHz not tested TBD TBD Supports OpenGL ES 3.0, OpenCL
Memory 1GB LPDDR3 @ 533MHz Works N/A N/A
Onboard Storage 8GB eMMC 4.51 Works TBD N/A

Initial Flash

The Dragonboard comes pre-installed with Android. For a quick and dirty flash, consult the Linux User Guide on http://www.96boards.org/products/ce/dragonboard410c/docs/. It guides you through a quick procedure that gets Linaro/Debian up and running.

We, however, want to build our own images. For that to work we need to download a couple of things. For that I'd suggest you create a dedicated directory; I called mine ~/dragonboard.

Preparations

Cross-compiler/-toolchain

To compile our stuff, we need a cross-compiler. For that, we use the fabulous crossdev tool.

Note
crossdev requires an overlay to store its newly generated ebuilds. If you don't want to pollute your existing ones, I'd suggest using -oO to create a custom one.
Note
If you run into problems with certain use-flags (like I did with go), use crossdev's --[x]env flag to modify it.
root #emerge crossdev
root #crossdev -t aarch64-unknown-linux-gnu -oO crossdev --genv 'USE="-go"'
---------------------------------------------------------------------------------
 * crossdev version:      20151026
 * Host Portage ARCH:     amd64
 * Target Portage ARCH:   arm64
 * Target System:         aarch64-unknown-linux-gnu
 * Stage:                 4 (C/C++ compiler)
 * ABIs:                  arm64

 * binutils:              binutils-[latest]
 * gcc:                   gcc-[latest]
 * headers:               linux-headers-[latest]
 * libc:                  glibc-[latest]

 * CROSSDEV_OVERLAY:      crossdev
 * PORT_LOGDIR:           /var/log/portage/
 * PORTAGE_CONFIGROOT:
 * Portage flags:

skales tools

We will further need the "skales" tools, which are basically a set of scripts.

user $cd ~/dragonboard
user $git clone git://codeaurora.org/quic/kernel/skales
Cloning into 'skales'...
remote: Counting objects: 276, done.
remote: Total 276 (delta 0), reused 0 (delta 0)
Receiving objects: 100% (276/276), 49.22 KiB | 39.00 KiB/s, done.
Resolving deltas: 100% (171/171), done.
Checking connectivity... done.

miscellanous tools

For those to work we will also need ftdget, which is a part of sys-apps/dtc. And for control- and flash-tasks we will need the fastboot utility from dev-util/android-tools.

root #emerge sys-apps/dtc dev-util/android-tools

Kernel

Gentoo-native sources provide drivers that have been accepted in mainline already.

But to get the latest and greatest from the 96boards and Linaro devs:

user $git clone https://github.com/96boards/linux/ db_410c_kernel
Cloning into 'db410c_kernel'...
remote: Counting objects: 4526190, done.
remote: Compressing objects: 100% (25/25), done.
remote: Total 4526190 (delta 24), reused 20 (delta 20), pack-reused 4526145
Receiving objects: 100% (4526190/4526190), 1.39 GiB | 255.00 KiB/s, done.
Resolving deltas: 100% (3737318/3737318), done.
Checking connectivity... done.
Checking out files: 100% (52502/52502), done.

boot.img

Kernel Compilation

First we need a configuration. I am going with the provided stock configs.

user $cd db_410c_kernel
user $make ARCH=arm64 CROSS_COMPILE=aarch64-unknown-linux-gnu- defconfig distro.conf

Then compile the kernel. Use a value corresponding to your compiling CPU's core-count for X - e.g. 4 or 5 for a quad-core.

user $make ARCH=arm64 CROSS_COMPILE=aarch64-unknown-linux-gnu- -jX

This will take a while. You can interrupt at any time, though, and resume with the same command.

Initrd / Initramfs

If you want to use upstream's initrd, get it here: http://builds.96boards.org/snapshots/dragonboard410c/linaro/debian/latest/

(The filename might differ slightly, so just browse the latest directory.)

Note
This step is not needed right now, as we will use upstream's initrd. Resume below.

Install the kernel's modules to a temporary directory and run depmod on them.

user $mkdir ../db_410c_modules/modules -p
user $cat include/config/kernel.release
4.4.0+   # kernel version

Be sure to get the version right or the kernel will not be able to find its modules later on.

root #depmod -a -b ../db_410c_modules/modules 4.4.0+
Note
resume here

Device Tree

We will assemble the boot.img in a separate directory, so change there.

user $mkdir ~/dragonboard/boot.img
user $cd ~/dragonboard/boot.img

Use the dtbTool from skales to assemble dt.img.

user $../skales/dtbTool -o dt.img -s 2048 \ ../db_410c_kernel/arch/arm64/boot/dts/qcom
Note
If you lack the dts/qcom directory, follow the instructions to compile the kernel above.

Assemble db410c-boot.img

You have several options here for your cmdline. Upstream suggests the following:

user $export cmdline="root=/dev/ram0 rw rootwait console=ttyMSM0,115200n8"
# This loads the rootfs from your ramdisk.
user $export cmdline="root=/dev/disk/by-partlabel/rootfs rw rootwait console=ttyMSM0,115200n8"
# This is your choice if you have a rootfs installed on your eMMC userdata partition.
user $export cmdline="root=/dev/disk/by-partlabel/rootfs rw rootwait console=ttyMSM0,115200n8 text"
# This just adds a text console.
user $../skales/mkbootimg --kernel ../db_410c_kernel/arch/arm64/boot/Image \
--ramdisk initrd.img-4.4.0-linaro-lt-qcom \
--output db410c-boot.img \
--dt dt.img \
--pagesize 2048 \
--base 0x80000000 \
--cmdline "${cmdline}"
Note
If mkbootimg fails, whining about AttributeError: 'bytes' object has no attribute 'encode', just edit it to call python2 instead of python.
Also note that, although similar in name, skales/mkbootimg is different from the binary provided by dev-embedded/u-boot-tools.

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