EBC Exercise 08 Installing Development Tools 4.4

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thumb‎ Embedded Linux Class by Mark A. Yoder


Early in the class most of the exercises we will do will all run on the BeagleBoard. You'll be able to edit (cloud9), compile (gcc) and run all on the Beagle. Later, when we start compiling the kernel or the boot loader, (U-boot) you will need to cross compile on a Linux machine and copy the results to the Beagle.

The purpose of this exercise is to install all the tools needed for compiling on your host so they will be ready when you need them.

Tip: Run this exercise using a wired connection if you can. The Ubuntu wireless driver can be finicky, and if it stops working you'll have to restart some of this.

The 4.4 Kernel

Getting the 4.4 Kernel

These notes taken from Beaglebone: Adding USB Wi-Fi & Building a Linux Kernel starting around 4 minutes and ending around 21 minutes. Uses kernel from Robert C. Nelson's BeagleBone Black page.

host$ git clone https://github.com/RobertCNelson/bb-kernel.git  (42M)
host$ cd bb-kernel
host$ git remote show origin

The last command lists all the versions of the kernel that are available. Pick one and check it out. I usually pick the one with the highest version number.

host$ git checkout am33x-v4.12
Branch am33x-v4.12 set up to track remote branch am33x-v4.12 from origin.
Switched to a new branch 'am33x-v4.12'
host$ ./build_kernel.sh
+ Detected build host [Ubuntu 14.04.4 LTS]
+ host: [x86_64]
+ git HEAD commit: [1bfef360bf49784906529778b681f6cafa32c566]
‘/home/yoder/BeagleBoard/bb-kernel/system.sh.sample’ -> ‘/home/yoder/BeagleBoard/bb-kernel/system.sh’
Installing: 
-----------------------------

At this point the scripts are downloading the crosscompiler, the kernel sources and anything else you need to compile the kernel for the bone.

Building the 4.4 Kernel

At some point you will see

KernelConfig2.png

Hit the right arrow to select Exit and then hit ENTER. The compilation will continue.

Installing the Kernel on Your Bone

The following are three ways you can use to install a new kernel on your Bone. You only need to use one method. I suggest you use the first one since you don't have to remove the SD card from the bone.

Copying to SD card on a running Bone

The Bone can have multiple versions of the kernel installed on it. It's possible to update the kernel on the Bone while it's running. After compiling on the host you need to install sshfs (you only need to do this once).

host$ sudo apt install sshfs 

Then copy may_install_kernel.sh to the bb-kernel directory.

host$ cd ~/BeagleBoard/bb-kernel
host$ cp ~/BeagleBoard/exercises/linux/kernel/may_install_kernel.sh tools

Now you can install the files using the following. Note, you must run may_install_kernel.sh from the directory above as shown.

host$ tools/may_install_kernel.sh
Mounting sshfs
-----------------------------
sshfs mounted
Installing 4.4.15-bone11 to sshfs
‘/home/yoder/BeagleBoard/bb-kernel/deploy/4.4.15-bone11.zImage’ -> ‘/home/yoder/BeagleBoard/bb-kernel/deploy/disk/zImage’
Installing 4.4.15-bone11-dtbs.tar.gz to sshfs
Installing 4.4.15-bone11 to sshfs
‘/home/yoder/BeagleBoard/bb-kernel/deploy/4.4.15-bone11.zImage’ -> ‘/home/yoder/BeagleBoard/bb-kernel/deploy/disk/boot/vmlinuz-4.4.15-bone11’
Installing 4.4.15-bone11-dtbs.tar.gz to sshfs
info: /boot/uEnv.txt: uname_r=4.4.15-bone11
Installing 4.4.15-bone11-modules.tar.gz to sshfs
tar: ./lib/modules/4.4.15-bone11/build: Cannot utime: No such file or directory
tar: ./lib/modules/4.4.15-bone11/source: Cannot utime: No such file or directory
tar: Exiting with failure status due to previous errors
‘/home/yoder/BeagleBoard/bb-kernel/deploy/config-4.4.15-bone11’ -> ‘/home/yoder/BeagleBoard/bb-kernel/deploy/disk/boot/config-4.4.15-bone11’
info: [4.4.15-bone11] now installed...

You may see about couple of error messages about build and source, but it seems to work anyway. If you look in /boot/uEvt.txt, you'll see it's ready to boot your new kernel.

bone$ head -3 /boot/uEnv.txt
#Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0

uname_r=4.4.15-bone11

If you change your mind about which kernel to boot, just edit the uname line.

Copying to the SD Card on Host

You can also install the kernel on an SD card that is mounted on your host computer. Plug it into your host and machine and run:

host$ tools/install_kernel.sh

This works like the may_install_kernel.sh, but it copies it to local host. Once copied, eject the SD card and plug it into your Bone and boot.

Updating and running off the eMMC

You can also update the eMMC to boot off a new kernel. EBC_Exercise_23_Configuring_the_Kernel#Making_and_Installing_the_kernel has instructions for copying the correct files to the eMMC to update the kernel.

Updating to a new version of the kernel

When you build your kernel the uImage file has some version information in the name. For example vmlinuz-4.4.21-ti-r47. The 4.4.21 is the version of the kernel and the -ti-r47 is the version of the patches applied to the kernel for the BeagleBone. Over time new patches will be posted. These instructions show how to get the latest version.

How do you know if you have the latest version? Run

bone$ uname -a
Linux yoder-debian-bone 4.4.21-ti-r47 #1 SMP Fri Sep 23 22:23:02 UTC 2016 armv7l GNU/Linux

This post to the Google Group lists the steps as "You need to recheckout master, delete your old branch and re-pull". Here's how you do it.

host$ cd linux-dev
host$ git checkout master
error: Your local changes to the following files would be overwritten by checkout:
	patches/defconfig
Please, commit your changes or stash them before you can switch branches.
Aborting

Hmm.... something has changed. See what it is.

host$ git diff patches/defconfig
diff --git a/patches/defconfig b/patches/defconfig
index d903776..3268287 100644
--- a/patches/defconfig
+++ b/patches/defconfig
@@ -2041,6 +2041,7 @@ CONFIG_JHD629_I2C=y
 # CONFIG_SERIAL_NONSTANDARD is not set
 # CONFIG_N_GSM is not set
 # CONFIG_TRACE_SINK is not set
+CONFIG_LPD8806=m
 CONFIG_DEVKMEM=y
 
 #

It looks like some configuration setting have changed. Since we are getting a new version of the kernel, let's revert back to the previous file and try again.

host$ git checkout patches/defconfig
host$ git checkout master
Switched to branch 'master'

Success, now step 2.

host$ git branch -d am33x-v3.8
warning: deleting branch 'am33x-v3.8' that has been merged to
         'refs/remotes/origin/am33x-v3.8', but not yet merged to HEAD.
Deleted branch am33x-v3.8 (was 3fc8a73).

Now repull

host$ git pull

Then start over again

host$ git checkout origin/am33x-v3.8 -b am33x-v3.8
Branch am33x-v3.8 set up to track remote branch am33x-v3.8 from origin.
Switched to a new branch 'am33x-v3.8'

Your system.sh file should be unchanged, so start building

host$ ./build_kernel.sh

Mine took some 26 minutes on an 8 core machine.

Recovering

If your Beagle fails to boot, follow the EBC_Exercise_22_Recovering instructions to recover.




thumb‎ Embedded Linux Class by Mark A. Yoder