CM-T43: Linux: Kernel - Revision history

Nikita: /* See also */

2016-06-29T11:27:23Z

‎See also

Nikita: /* Display support */

2016-01-24T16:26:23Z

‎Display support

Show changes

Nikita: /* Getting kernel sources */

2015-12-06T11:28:47Z

‎Getting kernel sources

Nikita at 11:27, 2 July 2015

2015-07-02T11:27:58Z

Grinberg: /* Git clone */

2015-04-19T18:15:48Z

‎Git clone

New page

== Overview ==
Linux kernel for the CompuLab CM-T43 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 CM-T43 modules.

== Device Tree ==

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.

A device tree file, named *.dts, is a text file that describes the hardware platform. It is compiled into a device tree blob, *.dtb, which is loaded into memory before the Linux kernel is started. The Linux kernel then uses that device tree blob to initialize itself at runtime.

CM-T43 DT related files are :

* {{filename | arch/arm/boot/dts/am437x-cm-t43.dts }} - CM-T43 core SoM/CoM Device Tree
* {{filename | arch/arm/boot/dts/compulab-sb-som.dtsi }} - SB-SOM baseboard Device Tree
* {{filename | arch/arm/boot/dts/am437x-sb-som-t43.dts }} - SB-SOM-T43 single board computer (eval board) Device Tree

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 CM-T43 ==
=== Cross-Compiler ===
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]")
* Pre-built toolchain (recommended):
** [http://www.mentor.com/embedded-software/sourcery-tools/sourcery-codebench/editions/lite-edition/ Sourcery CodeBench Lite]
* Tools for creating cross-compilers:
** [http://crosstool-ng.org/ Crosstool-ng]: Builds a cross-compiler from source. Non-distribution specific.
** [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 ===
There are various ways to get Linux kernel sources that can be used as a baseline for CM-T43 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 {{filename|/home/development/cm-t43/kernel}} directory structure has been created for CM-T43 kernel development.

==== Snapshot download ====
* Download [https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.19.tar.gz v3.19] snapshot with a web browser.
* Extract the downloaded archive {{filename|linux-3.19.tar.gz}}
<pre>
cd /home/development/cm-t43/kernel
tar xvf /path/to/downloaded/linux-3.19.tar.gz
mv linux-3.19 linux-cm-t43
</pre>
: This will create {{filename|/home/development/cm-t43/kernel/linux-cm-t43}} directory containing linux kernel tree.
* Apply the CM-T43 patch
<pre>
cd /home/development/cm-t43/kernel/linux-cm-t43
patch -p1 < /path/to/cm-t43-linux/kernel/linux-3.19.0-cm-t43-1.patch
</pre>

==== Git clone ====
* Install [http://git-scm.com/ git] version control system.
* Create a clone of linux kernel tree
<pre>
cd /home/development/cm-t43/kernel
git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux-cm-t43
</pre>
* Create a branch for CM-T43 development. The CM-T43 patches are generated vs. v3.19 tag (bfa76d49576599a4b9f9b7a71f23d73d6dcff735 commit) in the Linux tree. It is recommended to use exactly the same baseline to avoid merge conflicts.
<pre>
cd /home/development/cm-t43/kernel/linux-cm-t43
git checkout -b cm-t43-dev v3.19
</pre>
* Apply the CM-T43 patch
<pre>
git apply /path/to/cm-t43-linux/kernel/linux-3.19.0-cm-t43-1.patch
</pre>

{{Note|Future stable kernel versions of 3.19 can also be used by adding the Linux kernel stable repository as a remote and checking out any later tag of the v3.19.y stable kernel branch.}}

=== Building the kernel ===
* Run the following commands:
<pre>
export ARCH=arm
export CROSS_COMPILE=arm-none-linux-eabi-
make cm_t43_defconfig && make menuconfig
make && make zImage && make am437x-sb-som-t43.dtb \
INSTALL_MOD_PATH=/home/development/cm-t43/rootfs make modules_install
</pre>

In the example above:

* The Linux kernel image {{filename|zImage}} will be created in {{filename|/home/development/cm-t43/kernel/linux-cm-t43/arch/arm/boot}}
* The Device Tree binary {{filename|am437x-sb-som-t43.dtb}} will be created in {{filename|/home/development/cm-t43/kernel/linux-cm-t43/arch/arm/boot/dts}}
* The loadable kernel modules will be installed into the {{filename|/home/development/cm-t43/rootfs/lib/modules}} directory.

When the CM-T43 is booted with the kernel image and Device Tree binary created as described above and with networked root filesystem at {{filename|/home/development/cm-t43/rootfs/}}, the system will be able to load the kernel modules properly, thus avoiding module version problems.

== See also ==
* [[CM-T43: Linux: Getting started]]
* [[CM-T43: Linux: Debian]]

[[Category:Linux]]
[[Category:CM-T43]]

@@ Line 12: / Line 12: @@
 ==== Snapshot download ====
-* Download [https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.2.tar.gz v4.2] snapshot with a web browser.
+* Download [https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.4.13.tar.gz v4.4.13] snapshot with a web browser.
-* Extract the downloaded archive {{filename|linux-4.2.tar.gz}}
+* Extract the downloaded archive {{filename|linux-4.4.13.tar.gz}}
 <pre>
 cd /home/development/cm-t43/kernel
-tar xvf /path/to/downloaded/linux-4.2.tar.gz
+tar xvf /path/to/downloaded/linux-4.4.13.tar.gz
-mv linux-4.2 linux-cm-t43
+mv linux-4.4.13 linux-cm-t43
 </pre>
 : This will create {{filename|/home/development/cm-t43/kernel/linux-cm-t43}} directory containing linux kernel tree.
@@ Line 23: / Line 23: @@
 <pre>
 cd /home/development/cm-t43/kernel/linux-cm-t43
-patch -p1 < /path/to/cm-t43-linux/kernel/linux-4.2.0-cm-t43-4.patch
+patch -p1 < /path/to/cm-t43-linux/kernel/linux-4.4.13-cm-t43-5.patch
 </pre>
@@ Line 33: / Line 33: @@
 git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux-cm-t43
 </pre>
-* Create a branch for CM-T43 development. The CM-T43 patches are generated vs. v4.2 tag (64291f7db5bd8150a74ad2036f1037e6a0428df2 commit) in the Linux tree. It is recommended to use exactly the same baseline to avoid merge conflicts.
+* Create a branch for CM-T43 development. The CM-T43 patches are generated vs. v4.4.13 tag (ba760d4302e4fce130007b8bdbce7fcafc9bd9a9 commit) in the Linux tree. It is recommended to use exactly the same baseline to avoid merge conflicts.
 <pre>
 cd /home/development/cm-t43/kernel/linux-cm-t43
-git checkout -b cm-t43-dev v4.2
+git checkout -b cm-t43-dev v4.4.13
 </pre>
 * Apply the CM-T43 patch
 <pre>
-git apply /path/to/cm-t43-linux/kernel/linux-4.2.0-cm-t43-4.patch
+git apply /path/to/cm-t43-linux/kernel/linux-4.4.13-cm-t43-5.patch
 </pre>
-{{Note|Future stable kernel versions of 4.2 can also be used by adding the Linux kernel stable repository as a remote and checking out any later tag of the v4.2.y stable kernel branch.}}
+{{Note|Future stable kernel versions of 4.4.13 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.}}
 === Building the kernel ===
@@ Line 627: / Line 627: @@
 == See also ==
-* [[CM-T43: Linux: Getting started]]
+* [[CM-T43: Linux: Manual Installation]]
 * [[CM-T43: Linux: Debian]]
 [[Category:Linux]]
 [[Category:CM-T43]]

@@ Line 44: / Line 44: @@
 <pre>
 cd /home/development/cm-t43/kernel/linux-cm-t43
-patch -p1 < /path/to/cm-t43-linux/kernel/linux-3.19.0-cm-t43-1.patch
+patch -p1 < /path/to/cm-t43-linux/kernel/linux-3.19.0-cm-t43-2.patch
 </pre>
@@ Line 61: / Line 61: @@
 * Apply the CM-T43 patch
 <pre>
-git apply /path/to/cm-t43-linux/kernel/linux-3.19.0-cm-t43-1.patch
+git apply /path/to/cm-t43-linux/kernel/linux-3.19.0-cm-t43-2.patch
 </pre>