Building for BeagleBone

Arm Compiler

Setting up cross-compile environment is the first and necessary step. This will be used to compile your Bootloader, Kernel and the RootFile system for the beaglebone. The same applies to any board if the Host system is of a different architecture than the target system. Host in this case is your Laptop/Desktop where you will compile having x86 Intel Architecture almost certainly and the target is beaglebone having an ARM processor.

Linaro Toolchain

Linaro is an open organization focused on improving Linux on ARM. Toolchain Working Group provides the preferred community toolchain. These are prebuilt toolchains and just need to be moved to your appropriate bin directory which is available in the PATH environment variable while building.

Arch Linux : gcc-linaro-arm-linux-gnueabihf

Distro provided

The easier way is install the default compiler provided by your distribution.

Ubuntu : gcc-arm-linux-gnueabi

Arch Linux : arm-linux-gnueabi-gcc

• Tip: Do a alias in your environment, where N is the number of processors cores plus one:

$ alias armmake='make -jN ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- '

crosstool-NG

crosstool-NG aims at building toolchains. So, by this way you will build your own cross-compiler, but this requires that you choose an operation system and LibC. Therefore we will build a cross-compiler for Linux/gLibc.

U-Boot

Mainline U-boot

You can use the mainline u-boot for beaglebone.

Get:

$ git clone git://git.denx.de/u-boot.git

Clean:

$ armmake distclean

Configure for BeagleBone:

$ armmake am335x_evm_config

Build:

$ armmake

When the build is successfully completed, do check for these two files MLO and u-boot.img in the same directory, these will be used to boot the board.

Test your new U-Boot

You need a microSd card with 2Gb or more. In order to make U-Boot work you will need to create the first partion as FAT32 LBA, bootable, with something like 64 Megabytes.
This command wipes everything from your sdcard and creates that partition.

$ echo -e "o\nn\np\n1\n\n+64M\na\n1\nt\nc\nw\n" | sudo fdisk /dev/MYDISK ; sudo fdisk /dev/MYDISK -l

This comand should print something like:

Disk /dev/sdb: 7948 MB, 7948206080 bytes
16 heads, 4 sectors/track, 242560 cylinders, total 15523840 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x1c524301
    Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *        2048      133119       65536    c  W95 FAT32 (LBA)

The U-Boot compilation generated two files, MLO and uboot.img. Mount the partition that you just created and copy FIRST the MLO file to partition. Then copy the u-boot.img

$ sudo mount /dev/MYDISK /mnt
$ sudo cp MLO /mnt
$ sudo cp u-boot.img  /mnt
$ sudo sync
$ sudo umount  /mnt

Now with that sdcard in BeagleBone the output from serial should be:

IMP: To boot from the microSD card , u need to hold the button S2, this button is near the host USB port, on the other side of the ethernet port. If this is not held, the board may follow its default boot order and try booting from the onboard eMMC, if a uboot image is available on the onboard eMMC, our uboot image will not be built.

U-Boot SPL 2014.07-rc4-00264-g23f23f2-dirty (Jul 05 2014 - 21:56:58)
reading u-boot.img
reading u-boot.img


U-Boot 2014.07-rc4-00264-g23f23f2-dirty (Jul 05 2014 - 21:56:58)

I2C:   ready
DRAM:  512 MiB
NAND:  0 MiB
MMC:   OMAP SD/MMC: 0, OMAP SD/MMC: 1
*** Warning - readenv() failed, using default environment

Net:   <ethaddr> not set. Validating first E-fuse MAC
cpsw, usb_ether
Hit any key to stop autoboot:  0 
switch to partitions #0, OK
mmc0 is current device
SD/MMC found on device 0
reading uEnv.txt
** Unable to read file uEnv.txt **
** Invalid partition 2 **
switch to partitions #0, OK
mmc1(part 0) is current device
SD/MMC found on device 1
reading uEnv.txt
26 bytes read in 3 ms (7.8 KiB/s)
Loaded environment from uEnv.txt
Importing environment from mmc ...
** File not found /boot/zImage **
Booting from nand ...

no devices available

no devices available
Bad Linux ARM zImage magic!
U-Boot# 

If you don't see this output, but sees a bunch of "CCCCC", this could mean that the first partition doesn't have the boot flag set.

There are two problems in this output. First, you don't have a uEnv.txt, which configure the U-Boot and secondly you don't have a linux image. But first check what is the default environment from Beaglebone. Boot the u-boot and do a pr command, the output should be like this:

U-Boot# pr
arch=arm
baudrate=115200
board=am335x
board_name=A335BNLT
board_rev=0A5A
boot_fdt=try
bootargs=console=ttyO0,115200n8 quiet drm.debug=7 root=ubi0:rootfs rw ubi.mtd=7,2048 rootfstype=ubifs rootwait=1
bootcmd=run findfdt; run mmcboot;setenv mmcdev 1; setenv bootpart 1:2; run mmcboot;run nandboot;

bootcount=1
bootdelay=1
bootdir=/boot
bootenv=uEnv.txt
bootfile=zImage
bootm_size=0x10000000
bootpart=1:2
console=ttyO0,115200n8
cpu=armv7
dfu_alt_info_emmc=rawemmc mmc 0 3751936
dfu_alt_info_mmc=boot part 0 1;rootfs part 0 2;MLO fat 0 1;MLO.raw mmc 0x100 0x100;u-boot.img.raw mmc 0x300 0x400;spl-os-args.raw mmc 0x80 0x80;spl-os-image.raw mmc 0x900 0x2000;spl-os-args fat 0 1;spl-os-image fat 0 1;u-boot.img fat 0 1;uEnv.txt fat 0 1
dfu_alt_info_nand=SPL part 0 1;SPL.backup1 part 0 2;SPL.backup2 part 0 3;SPL.backup3 part 0 4;u-boot part 0 5;u-boot-spl-os part 0 6;kernel part 0 8;rootfs part 0 9
dfu_alt_info_ram=kernel ram 0x80200000 0xD80000;fdt ram 0x80F80000 0x80000;ramdisk ram 0x81000000 0x4000000
eth1addr=c8:a0:30:a6:2c:6f
ethact=cpsw
ethaddr=c8:a0:30:a6:2c:6d
fdt_addr_r=0x88000000
fdtaddr=0x88000000
fdtfile=am335x-boneblack.dtb
filesize=1a
findfdt=if test $board_name = A335BONE; then setenv fdtfile am335x-bone.dtb; fi; if test $board_name = A335BNLT; then setenv fdtfile am335x-boneblack.dtb; fi; if test $board_name = A33515BB; then setenv fdtfile am335x-evm.dtb; fi; if test $board_name = A335X_SK; then se
importbootenv=echo Importing environment from mmc ...; env import -t $loadaddr $filesize
kernel_addr_r=0x82000000
loadaddr=0x82000000
loadbootenv=load mmc ${mmcdev} ${loadaddr} ${bootenv}
loadfdt=load mmc ${bootpart} ${fdtaddr} ${bootdir}/${fdtfile}
loadimage=load mmc ${bootpart} ${loadaddr} ${bootdir}/${bootfile}
loadramdisk=load mmc ${mmcdev} ${rdaddr} ramdisk.gz
mmcargs=setenv bootargs console=${console} ${optargs} root=${mmcroot} rootfstype=${mmcrootfstype}
mmcboot=mmc dev ${mmcdev}; if mmc rescan; then echo SD/MMC found on device ${mmcdev};if run loadbootenv; then echo Loaded environment from ${bootenv};run importbootenv;fi;if test -n $uenvcmd; then echo Running uenvcmd ...;run uenvcmd;fi;if run loadimage; then run mmcloa;
mmcdev=1
mmcloados=run mmcargs; if test ${boot_fdt} = yes || test ${boot_fdt} = try; then if run loadfdt; then bootz ${loadaddr} - ${fdtaddr}; else if test ${boot_fdt} = try; then bootz; else echo WARN: Cannot load the DT; fi; fi; else bootz; fi;
mmcroot=/dev/mmcblk0p2 ro
mmcrootfstype=ext4 rootwait
mtdids=nand0=omap2-nand.0
mtdparts=mtdparts=omap2-nand.0:128k(SPL),128k(SPL.backup1),128k(SPL.backup2),128k(SPL.backup3),1792k(u-boot),128k(u-boot-spl-os),128k(u-boot-env),5m(kernel),-(rootfs)
nandargs=setenv bootargs console=${console} ${optargs} root=${nandroot} rootfstype=${nandrootfstype}
nandboot=echo Booting from nand ...; run nandargs; nand read ${fdtaddr} u-boot-spl-os; nand read ${loadaddr} kernel; bootz ${loadaddr} - ${fdtaddr}
nandroot=ubi0:rootfs rw ubi.mtd=7,2048
nandrootfstype=ubifs rootwait=1
netargs=setenv bootargs console=${console} ${optargs} root=/dev/nfs nfsroot=${serverip}:${rootpath},${nfsopts} rw ip=dhcp
netboot=echo Booting from network ...; setenv autoload no; dhcp; tftp ${loadaddr} ${bootfile}; tftp ${fdtaddr} ${fdtfile}; run netargs; bootz ${loadaddr} - ${fdtaddr}
nfsopts=nolock
optargs=quiet drm.debug=7
partitions=uuid_disk=${uuid_gpt_disk};name=rootfs,start=2MiB,size=-,uuid=${uuid_gpt_rootfs}
ramargs=setenv bootargs console=${console} ${optargs} root=${ramroot} rootfstype=${ramrootfstype}
ramboot=echo Booting from ramdisk ...; run ramargs; bootz ${loadaddr} ${rdaddr} ${fdtaddr}
ramdisk_addr_r=0x88080000
ramroot=/dev/ram0 rw
ramrootfstype=ext2
rdaddr=0x88080000
rootpath=/export/rootfs
soc=am33xx
spiargs=setenv bootargs console=${console} ${optargs} root=${spiroot} rootfstype=${spirootfstype}
spiboot=echo Booting from spi ...; run spiargs; sf probe ${spibusno}:0; sf read ${loadaddr} ${spisrcaddr} ${spiimgsize}; bootz ${loadaddr}
spibusno=0
spiimgsize=0x362000
spiroot=/dev/mtdblock4 rw
spirootfstype=jffs2
spisrcaddr=0xe0000
static_ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}:${hostname}::off
stderr=serial
stdin=serial
stdout=serial
usbnet_devaddr=c8:a0:30:a6:2c:6f
vendor=ti
ver=U-Boot 2014.07-rc4-00264-g23f23f2-dirty (Jul 05 2014 - 21:56:58)

Some of these configs comes from "u-boot/include/configs/am335x_evm.h". These configs can be changed, but u-boot needs to be recompiled in order to take effect. But, the most common way is change configs in a file called uEnv.txt. This file is read in boot time, and override any configuration pre-defined in beaglebone.

This is the basic uEnv.txt that your boards needs in order to boot your kernel. Create and put this file uEnv.txt in your boot partition.

bootdir=
bootfile=zImage
fdtfile=am335x-boneblack.dtb
loadaddr=0x80007fc0
fdtaddr=0x80F80000
loadfdt=fatload mmc 0:1 ${fdtaddr} ${fdtfile}
loaduimage=fatload mmc 0:1 ${loadaddr} ${bootfile}
uenvcmd=mmc rescan; run loaduimage; run loadfdt; run fdtboot
fdtboot=run mmc_args; run mmcargs; bootz ${loadaddr} - ${fdtaddr}
mmc_args=setenv bootargs console=${console} ${optargs} root=${mmcroot} rootfstype=${mmcrootfstype}

_{Subscript text}

Kernel

Mainline Kernel

You can use the mainline linux for beaglebone.

Get:

$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

Clean:

$ armmake distclean

Configure for BeagleBone:

$ armmake multi_v7_defconfig

Check if two remaining configs are set:

│ Symbol: MFD_TPS65217 [=n]
│ Type  : tristate
│ Prompt: TI TPS65217 Power Management / White LED chips
│   Location:
│     -> Device Drivers
│ (1)   -> Multifunction device drivers
│   Defined at drivers/mfd/Kconfig:877
│   Depends on: HAS_IOMEM [=y] && I2C [=y]
│   Selects: MFD_CORE [=y] && REGMAP_I2C [=y]

│ Symbol: REGULATOR_TPS65217 [=n]
│ Type  : tristate
│ Prompt: TI TPS65217 Power regulators
│   Location:
│     -> Device Drivers
│ (1)   -> Voltage and Current Regulator Support (REGULATOR [=y])
│   Defined at drivers/regulator/Kconfig:554
│   Depends on: REGULATOR [=y] && MFD_TPS65217 [=y]

Build:

$ armmake

After build, there are two important files. Linux kernel at arch/arm/boot/zImage and Device Tree Blob arch/arm/boot/dts/am335x-boneblack.dtb or arch/arm/boot/dts/am335x-bone.dtb (for white). So copy that to memory card.

$ sudo cp arch/arm/boot/zImage /mnt
$ sudo cp arch/arm/boot/dts/am335x-boneblack.dtb /mnt

Test your new Kernel

Now your kernel is able to boot. But finish this way:

[1.507789] EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null)
[1.516423] VFS: Mounted root (ext4 filesystem) readonly on device 179:2.
[1.525636] devtmpfs: error mounting -2
[1.530467] Freeing unused kernel memory: 728K (c0b90000 - c0c46000)
[1.537240] Kernel panic - not syncing: No working init found. Try passing init= option to kernel. See Linux Documentation/init.txt for guidance.
[1.551022] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.18.0-rc3-00134-gfe606df #1
[1.559008] [<c02162c0>] (unwind_backtrace) from [<c0211cc4>] (show_stack+0x10/0x14)
[1.567139] [<c0211cc4>] (show_stack) from [<c0896d64>] (dump_stack+0x8c/0x9c)
[1.574716] [<c0896d64>] (dump_stack) from [<c08964d0>] (panic+0xa0/0x218)
[1.581929] [<c08964d0>] (panic) from [<c089488c>] (cpu_die+0x0/0x80)
[1.588682] [<c089488c>] (cpu_die) from [<00000000>] ( (null))
[1.594897] ---[ end Kernel panic - not syncing: No working init found. Try passing init= option to kernel. See Linux Documentation/init.txt for guidance.

This means that your board doesn't have a root file system.

NOTE: I faced a issue where the boot process got stuck at.

In some case , the boot may be stuck at

[    1.645505] Waiting for root device ... 
[    1.654437] mmc1: new high speed MMC card at address 0001
[    1.660920] mmcblk1: mmc1:0001 S10004 3.56 GiB 
[    1.666011] mmcblk1boot0: mmc1:0001 S10004 partition 1 4.00 MiB 
[    1.672479] mmcblk1boot1: mmc1:0001 S10004 partition 2 4.00 MiB 
[    1.679915]  mmcblk1: p1 p2

The reason being the root partition was not being passed correctly, we need to make changes in th uEnv.txt file that we created before.

This was the original uEnv.txt file,

bootdir=                                                         
bootfile=zImage 
fdtfile=am335x-boneblack.dtb
loadaddr=0x80007fc0
fdtaddr=0x80F80000
loadfdt=fatload mmc 0:1 ${fdtaddr} ${fdtfile}
loaduimage=fatload mmc 0:1 ${loadaddr} ${bootfile}     
uenvcmd=mmc rescan; run loaduimage; run loadfdt; run fdtboot
fdtboot=run mmc_args; run mmcargs; bootz ${loadaddr} - ${fdtaddr}
mmc_args=setenv bootargs console=${console} ${optargs} root=${mmcroot} rootfstype=${mmcrootfstype}

I modified the last line as ,

mmc_args=setenv bootargs console=${console} ${optargs} root=/dev/mmcblk0p2 rootfstype=ext4

to mark our microSD card's second partition as the root device, that will have our root file system.

-mmcblk0(microSD)
----mmcblk0p1 (partition1)
----mmvblk0p2 (partition2)
-mmcblk1(onboard eMMC)
----mmcblk1p1 (partition1)
----mmcblk1p2 (partition2)

Root File System

To create a root file system we need BuildRoot.

Clone the source:

$ git clone git://git.buildroot.net/buildroot

Configure buildroot for Beaglebone:

$ make beaglebone_defconfig

Let's do some tweaking.

$ make menuconfig

• Uncheck Kernel, you just built yours.
• Ucheck bootloaders --> u-boot, you just built yours.
• Target options --->:
  • Floating point strategy (NEON)
  • ARM instruction set (Thumb2)
• Toolchain --->
  • Toolchain type (External toolchain)
  • Toolchain (Linaro ARM 2014.08)
  • Toolchain origin (Pre-installed toolchain)
  • (/opt/gcc-linaro-arm-linux-gnueabihf) Toolchain path
• Target packages --->
  • Networking applications --->
    • [*] dhcpcd
    • [*] openssh
  • Text editors and viewers --->
    • [*] nano
• Filesystem images --->
  • ext2/3/4 variant (ext4) --->
    • (X) ext4

Now save and exit.

Build the root file system:

$ make

If the build fails, asking for the zImage and the dts files, just copy the ones we generated while building the kernel into the output/images/ directory of the buildroot environment.

Finally you can flash the rootfs image to sdcard:

$ sudo dd if=buildroot/output/images/rootfs.ext4 of=/dev/sdc2

The end:

Welcome to Buildroot
beaglebone login:

The default user is "root" without any password.