Difference between revisions of "CL-SOM-AM57x: Linux: Kernel"

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Linux kernel for the CompuLab CL-SOM-AM57x System-on-Module / Computer-on-Module provides support for on-board peripherals and abstracts the functionality provided by the hardware.
 
Linux kernel for the CompuLab CL-SOM-AM57x System-on-Module / Computer-on-Module provides support for on-board peripherals and abstracts the functionality provided by the hardware.
 
CompuLab provides ready-to-run binary kernel images, and source code of the modifications and additions made to the Linux kernel to work properly with CL-SOM-AM57x modules.
 
CompuLab provides ready-to-run binary kernel images, and source code of the modifications and additions made to the Linux kernel to work properly with CL-SOM-AM57x modules.
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== Device Tree ==
 
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Device Tree (DT), is a data structure and language for describing hardware. More specifically, it is a description of hardware that is readable by an operating system so that the operating system doesn't need to hard code details of the machine.
 
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A device tree file, named {{filename|*.dts}}, is a text file that describes the hardware platform.
 
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It is compiled into a device tree blob, {{filename|*.dtb}}, which is loaded into memory before the Linux kernel is started.
 
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The Linux kernel then uses that device tree blob to initialize itself at runtime.
 
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CL-SOM-AM57x DT related files are :
 
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* {{filename | arch/arm/boot/dts/am57xx-cl-som-am57x.dts }} - CL-SOM-AM57x core SoM/CoM Device Tree that can be used with almost any base board.
 
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* {{filename | arch/arm/boot/dts/compulab-sb-som.dtsi }} - SB-SOM baseboard Device Tree.
 
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* {{filename | arch/arm/boot/dts/am57xx-sbc-am57x.dts }} - SBC-AM57x single board computer (eval board) Device Tree.
 
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For more details visit official [http://devicetree.org/Device_Tree_Usage Device Tree WiKi] pages and make an overview of a [http://events.linuxfoundation.org/sites/events/files/slides/petazzoni-device-tree-dummies.pdf  Device Tree tutorial].
 
  
 
== Building kernel for CL-SOM-AM57x ==
 
== Building kernel for CL-SOM-AM57x ==
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=== Cross-Compiler ===
 
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There are several options for cross-compilation toolchain setup. You can either compile your cross-compiler or use an already built cross-compiler. The cross-compiler should support the ARM embedded-application binary interface ("[http://en.wikipedia.org/wiki/Application_binary_interface#EABI EABI]")
 
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* Pre-built toolchain (recommended):
 
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** [http://www.mentor.com/embedded-software/sourcery-tools/sourcery-codebench/editions/lite-edition/ Sourcery CodeBench Lite]
 
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* Tools for creating cross-compilers:
 
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** [http://crosstool-ng.org/ Crosstool-ng]: Builds a cross-compiler from source. Non-distribution specific.
 
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** [http://www.gentoo.org/proj/en/base/embedded/handbook/index.xml?part=1&chap=4 Crossdev]: Gentoo's cross-compiler builder. Needs Gentoo.
 
  
 
=== Getting kernel sources ===
 
=== Getting kernel sources ===
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==== Snapshot download ====
 
==== Snapshot download ====
 +
===== Mainline kernel v4.4 =====
 
* Download [https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.4.tar.gz v4.4] snapshot with a web browser.
 
* Download [https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.4.tar.gz v4.4] snapshot with a web browser.
 
* Extract the downloaded archive {{filename|linux-4.4.tar.gz}}
 
* Extract the downloaded archive {{filename|linux-4.4.tar.gz}}
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<pre>
 
<pre>
 
cd /home/development/cl-som-am57x/kernel/cl-som-am57x
 
cd /home/development/cl-som-am57x/kernel/cl-som-am57x
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patch -p1 < /path/to/cl-som-am57x/kernel/linux-4.4-cl-som-am57x-2.patch
+
patch -p1 < /path/to/cl-som-am57x/kernel/linux-4.4-cl-som-am57x-2.1.patch
 +
</pre>
 +
===== TI SDK kernel v4.1.13 =====
 +
* Download [https://git.ti.com/processor-sdk/processor-sdk-linux/archive-tarball/processor-sdk-linux-02.00.01 v4.1.13] snapshot with a web browser.
 +
<pre>
 +
cd /home/development/cl-som-am57x/kernel
 +
tar xvf /path/to/downloaded/processor-sdk-processor-sdk-linux-processor-sdk-linux-02.00.01.tar.gz
 +
mv processor-sdk-linux linux-cl-som-am57x-ti
 +
</pre>
 +
: This will create {{filename|/home/development/cl-som-am57x/kernel/linux-cl-som-am57x-ti}} directory containing linux kernel tree.
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* Apply the CL-SOM-AM57x patch
 +
<pre>
 +
cd /home/development/cl-som-am57x/kernel/cl-som-am57x-ti
 +
patch -p1 < /path/to/cl-som-am57x/kernel/ti-sdk-4.1.13/linux-4.1.13-cl-som-am57x-2.1.patch
 
</pre>
 
</pre>
−
 
 
==== Git clone ====
 
==== Git clone ====
 
* Install [http://git-scm.com/ git] version control system.
 
* Install [http://git-scm.com/ git] version control system.
 +
===== Mainline kernel v4.4 =====
 
* Create a clone of linux kernel tree
 
* Create a clone of linux kernel tree
 
<pre>
 
<pre>
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git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux-cl-som-am57x
 
git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux-cl-som-am57x
 
</pre>
 
</pre>
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* Create a branch for CL-SOM-AM57x development. The CL-SOM-AM57x patches are generated vs. v4.3 tag (b5be40b90dbaa6bd337f3b77de361bfc0723468b commit) in the Linux tree. It is recommended to use exactly the same baseline to avoid merge conflicts.
+
* Create a branch for CL-SOM-AM57x development. The CL-SOM-AM57x patches are generated vs. v4.4 tag (b5be40b90dbaa6bd337f3b77de361bfc0723468b commit) in the Linux tree. It is recommended to use exactly the same baseline to avoid merge conflicts.
 
<pre>
 
<pre>
 
cd /home/development/cl-som-am57x/kernel/linux-cl-som-am57x
 
cd /home/development/cl-som-am57x/kernel/linux-cl-som-am57x
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* Apply the CL-SOM-AM57x patch
 
* Apply the CL-SOM-AM57x patch
 
<pre>
 
<pre>
−
git apply /path/to/cl-som-am57x-linux/kernel/linux-4.4-cl-som-am57x-2.patch
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git apply /path/to/cl-som-am57x-linux/kernel/linux-4.4-cl-som-am57x-2.1.patch
 
</pre>
 
</pre>
  
 
{{Note|Future stable kernel versions of 4.4 can also be used by adding the Linux kernel stable repository as a remote and checking out any later tag of the v4.4.y stable kernel branch.}}
 
{{Note|Future stable kernel versions of 4.4 can also be used by adding the Linux kernel stable repository as a remote and checking out any later tag of the v4.4.y stable kernel branch.}}
 +
===== TI SDK kernel v4.1.13 =====
 +
* Create a clone of linux kernel tree
 +
<pre>
 +
cd /home/development/cl-som-am57x/kernel
 +
git clone git://git.ti.com/processor-sdk/processor-sdk-linux.git linux-cl-som-am57x-ti
 +
</pre>
 +
* Create a branch for CL-SOM-AM57x development. The CL-SOM-AM57x patches are generated vs. processor-sdk-linux-rt-02.00.01 branch in the TI Linux tree. It is recommended to use exactly the same baseline to avoid merge conflicts.
 +
<pre>
 +
cd /home/development/cl-som-am57x/kernel/linux-cl-som-am57x-ti
 +
git checkout -b cl-som-am57x-dev-ti origin/processor-sdk-linux-02.00.01
 +
</pre>
 +
{{Note|As an alternative, the TI SDK kernel can be added as an additional remote to the mainline kernel git repository.}}
 +
* Apply the CL-SOM-AM57x patch
 +
<pre>
 +
git apply /path/to/cl-som-am57x-linux/kernel/ti-sdk-4.1.13/linux-4.1.13-cl-som-am57x-2.1.patch
 +
</pre>
  
 
=== Building the kernel ===
 
=== Building the kernel ===

Revision as of 16:21, 24 March 2016

Overview

Linux kernel for the CompuLab CL-SOM-AM57x System-on-Module / Computer-on-Module provides support for on-board peripherals and abstracts the functionality provided by the hardware. CompuLab provides ready-to-run binary kernel images, and source code of the modifications and additions made to the Linux kernel to work properly with CL-SOM-AM57x modules.

Building kernel for CL-SOM-AM57x

Getting kernel sources

There are various ways to get Linux kernel sources that can be used as a baseline for CL-SOM-AM57x kernel. For instance, a copy of linux-stable git tree can be created or a Linux kernel sources snapshot can be downloaded.

Assuming that the /home/development/cl-som-am57x/kernel directory structure has been created for CL-SOM-AM57x kernel development.

Snapshot download

Mainline kernel v4.4
  • Download v4.4 snapshot with a web browser.
  • Extract the downloaded archive linux-4.4.tar.gz
cd /home/development/cl-som-am57x/kernel
tar xvf /path/to/downloaded/linux-4.4.tar.gz
mv linux-4.4 linux-cl-som-am57x
This will create /home/development/cl-som-am57x/kernel/linux-cl-som-am57x directory containing linux kernel tree.
  • Apply the CL-SOM-AM57x patch
cd /home/development/cl-som-am57x/kernel/cl-som-am57x
patch -p1 < /path/to/cl-som-am57x/kernel/linux-4.4-cl-som-am57x-2.1.patch
TI SDK kernel v4.1.13
  • Download v4.1.13 snapshot with a web browser.
cd /home/development/cl-som-am57x/kernel
tar xvf /path/to/downloaded/processor-sdk-processor-sdk-linux-processor-sdk-linux-02.00.01.tar.gz
mv processor-sdk-linux linux-cl-som-am57x-ti
This will create /home/development/cl-som-am57x/kernel/linux-cl-som-am57x-ti directory containing linux kernel tree.
  • Apply the CL-SOM-AM57x patch
cd /home/development/cl-som-am57x/kernel/cl-som-am57x-ti
patch -p1 < /path/to/cl-som-am57x/kernel/ti-sdk-4.1.13/linux-4.1.13-cl-som-am57x-2.1.patch

Git clone

  • Install git version control system.
Mainline kernel v4.4
  • Create a clone of linux kernel tree
cd /home/development/cl-som-am57x/kernel
git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux-cl-som-am57x
  • Create a branch for CL-SOM-AM57x development. The CL-SOM-AM57x patches are generated vs. v4.4 tag (b5be40b90dbaa6bd337f3b77de361bfc0723468b commit) in the Linux tree. It is recommended to use exactly the same baseline to avoid merge conflicts.
cd /home/development/cl-som-am57x/kernel/linux-cl-som-am57x
git checkout -b cl-som-am57x-dev v4.4
  • Apply the CL-SOM-AM57x patch
git apply /path/to/cl-som-am57x-linux/kernel/linux-4.4-cl-som-am57x-2.1.patch


Admolition note.png Future stable kernel versions of 4.4 can also be used by adding the Linux kernel stable repository as a remote and checking out any later tag of the v4.4.y stable kernel branch.
TI SDK kernel v4.1.13
  • Create a clone of linux kernel tree
cd /home/development/cl-som-am57x/kernel
git clone git://git.ti.com/processor-sdk/processor-sdk-linux.git linux-cl-som-am57x-ti
  • Create a branch for CL-SOM-AM57x development. The CL-SOM-AM57x patches are generated vs. processor-sdk-linux-rt-02.00.01 branch in the TI Linux tree. It is recommended to use exactly the same baseline to avoid merge conflicts.
cd /home/development/cl-som-am57x/kernel/linux-cl-som-am57x-ti
git checkout -b cl-som-am57x-dev-ti origin/processor-sdk-linux-02.00.01
Admolition note.png As an alternative, the TI SDK kernel can be added as an additional remote to the mainline kernel git repository.
  • Apply the CL-SOM-AM57x patch
git apply /path/to/cl-som-am57x-linux/kernel/ti-sdk-4.1.13/linux-4.1.13-cl-som-am57x-2.1.patch

Building the kernel

  • Run the following commands:
export ARCH=arm
export CROSS_COMPILE=arm-none-linux-eabi-
make cl-som-am57x_defconfig && make menuconfig
make && make zImage && make am57xx-sbc-am57x.dtb \
     INSTALL_MOD_PATH=/home/development/cl-som-am57x/rootfs make modules_install

In the example above:

  • The Linux kernel image zImage will be created in /home/development/cl-som-am57x/kernel/linux-cl-som-am57x/arch/arm/boot
  • The Device Tree binary am57xx-sbc-am57x.dtb will be created in /home/development/cl-som-am57x/kernel/linux-cl-som-am57x/arch/arm/boot/dts
  • The loadable kernel modules will be installed into the /home/development/cl-som-am57x/rootfs/lib/modules directory.

When the CL-SOM-AM57x is booted with the kernel image and Device Tree binary created as described above and with networked root filesystem at /home/development/cl-som-am57x/rootfs/, the system will be able to load the kernel modules properly, thus avoiding module version problems.

See also

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