Linux Kernel - 6.6

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Linux 6.6 for MPU source code

The Linux kernel for Microchip ARM-Based MPUs (aka AT91) is distributed as a GIT tree hosted on GitHub as a fork of the official Linus Torvalds' git tree. The objective of the Microchip Linux team is to integrate all the AT91-related material in the official Linux Kernel.
Before completing this inclusion process, which can take time, this website provides the Linux4SAM Linux Kernel git tree for AT91 devices at:

https://github.com/linux4microchip/linux/tree/linux-6.6-mchp

Tags

linux4microchip-2024.04 tag

Enhancements are added on top of the official v6.6 Linux kernel tag where most of the Microchip SoC features are already supported. Note as well that we re-integrate each and every stable kernel release on top of this Long Term Support (LTS) kernel revision. This means that each v6.6.x version is merged in our branch.

Here is a little summary of the main additional enhancements:

• Integration of stable kernel updates up to v6.6.23
• Add support for SAM9x75 Curiosity board

Required packages

You must install essential host packages on your build host. These requirements are listed in the Linux kernel documentation with the chapter Install build requirements. You must follow this process which includes, but not limited to, the following packages:

• build-essential
  
• flex
  
• bison
  
• git
  
• perl-base
  
• libssl-dev
  
• libncurses5-dev
  
• libncursesw5-dev
  
• ncurses-dev
  

Getting Kernel sources

To get the source code, you have to clone the repository:

$ git clone https://github.com/linux4microchip/linux.git
Cloning into 'linux'...
remote: Enumerating objects: 8587836, done.
remote: Total 8587836 (delta 0), reused 0 (delta 0), pack-reused 8587836
Receiving objects: 100% (8587836/8587836), 3.49 GiB | 13.44 MiB/s, done.
Resolving deltas: 100% (7117887/7117887), done.
Updating files: 100% (70687/70687), done.
$ cd linux

The source code has been taken from the master branch which is pointing on the latest branch we use.

Note that you can also add this Linux4SAM repository as a remote GIT repository to your usual Linux git tree. It will save you a lot of bandwidth and download time:

$ git remote add linux4microchip https://github.com/linux4microchip/linux.git
$ git remote update linux4microchip
Fetching linux4microchip
From https://github.com/linux4microchip/linux
 * [new branch]                linux-6.1-mchp -> linux4microchip/linux-6.1-mchp
 * [new branch]                linux-6.6-mchp -> linux4microchip/linux-6.6-mchp
 * [new branch]                master     -> linux4microchip/master

If you want to use another branch, you can list them and use one of them by doing this:

$ git branch -r
  linux4microchip/linux-5.10-mchp
  linux4microchip/linux-5.15-mchp
  linux4microchip/linux-5.15-mchp+fpga
  linux4microchip/linux-6.1-mchp
  linux4microchip/linux-6.1-mchp+fpga
  linux4microchip/linux-6.6-mchp
  linux4microchip/linux-6.6-mchp+fpga
  linux4microchip/master
$ git checkout -b linux-6.6-mchp --track remotes/linux4microchip/linux-6.6-mchp
Branch linux-6.6-mchp set up to track remote branch linux-6.6-mchp from linux4microchip.
Switched to a new branch 'linux-6.6-mchp'

Setup ARM Cross Compiler

• First step is to dowload the ARM GNU Toolchain:
  

  wget -c https://developer.arm.com/-/media/Files/downloads/gnu/13.2.rel1/binrel/arm-gnu-toolchain-13.2.rel1-x86_64-arm-none-linux-gnueabihf.tar.xz
     

• Next step is to add the ARM GNU Toolchain into your system:
  

  tar -xf arm-gnu-toolchain-13.2.rel1-x86_64-arm-none-linux-gnueabihf.tar.xz
  export CROSS_COMPILE=`pwd`/arm-gnu-toolchain-13.2.rel1-x86_64-arm-none-linux-gnueabihf/bin/arm-none-linux-gnueabihf-
      

  or

  tar -xf arm-gnu-toolchain-13.2.rel1-x86_64-arm-none-linux-gnueabihf.tar.xz
  export CROSS_COMPILE=arm-none-linux-gnueabihf-
  export PATH=$PATH:/YOUR/PATH/TO/arm-gnu-toolchain-13.2.Rel1-x86_64-arm-none-linux-gnueabihf/bin/
     

• !Note: If you already have an old ARM GNU Toolchain need to clean up the PATH with:
  

  export PATH=${PATH/':/YOUR/PATH/TO/arm-gnu-toolchain-VERSION-x86_64-arm-none-linux-gnueabihf/bin/'/}
      

Configure and Build the Linux kernel

Now you have to configure the Linux kernel according to your hardware. We have two default configuration at91 SoC in arch/arm/configs

arch/arm/configs/at91_dt_defconfig
arch/arm/configs/sama5_defconfig
arch/arm/configs/sama7_defconfig

• at91_dt_defconfig: for SAM9 (ARM926) series chips
• sama5_defconfig: for SAMA5 series chips
• sama7_defconfig: for SAMA7 series chips

Now we Configure and Build kernel for board:

$ make ARCH=arm sama5_defconfig
  HOSTCC  scripts/basic/fixdep
  HOSTCC  scripts/kconfig/conf.o
  SHIPPED scripts/kconfig/zconf.tab.c
  SHIPPED scripts/kconfig/zconf.lex.c
  SHIPPED scripts/kconfig/zconf.hash.c
  HOSTCC  scripts/kconfig/zconf.tab.o
  HOSTLD  scripts/kconfig/conf
#
# configuration written to .config
#

At this step, you can modify default configuration using the menuconfig

$ make ARCH=arm menuconfig

Now, in the menuconfig dialog, you can easily add or remove some features. Once done, Move to <Exit> with arrows and press this button hitting the Enter key to exit from this screen.

Build the Linux kernel image, before you build you need set up the cross compile toolchain, check this section.

$ make ARCH=arm

[..]

  Kernel: arch/arm/boot/Image is ready
  Kernel: arch/arm/boot/zImage is ready

Now you have an usable compressed kernel image zImage.

If you need an uImage you can run this additional step:

make ARCH=arm uImage LOADADDR=0x20008000

[..]

  Kernel: arch/arm/boot/zImage is ready
  UIMAGE  arch/arm/boot/uImage
  Image Name:   Linux-6.6.23-linux4microchip-202
  Created:      Thu May 16 14:36:06 2024
  Image Type:   ARM Linux Kernel Image (uncompressed)
  Data Size:    5221704 Bytes = 5099.32 KiB = 4.98 MiB
  Load Address: 20008000
  Entry Point:  20008000
  Kernel: arch/arm/boot/uImage is ready

make ARCH=arm dtbs

[..]

  DTC     arch/arm/boot/dts/microchip/at91-sam9x60_curiosity.dtb
  DTC     arch/arm/boot/dts/microchip/at91-sam9x60ek.dtb
  DTC     arch/arm/boot/dts/microchip/at91-sam9x75_curiosity.dtb
  DTC     arch/arm/boot/dts/microchip/at91-sam9x75eb.dtb  
  DTC     arch/arm/boot/dts/microchip/at91-sama5d27_som1_ek.dtb
  DTC     arch/arm/boot/dts/microchip/at91-sama5d27_wlsom1_ek.dtb
  DTC     arch/arm/boot/dts/microchip/at91-sama5d29_curiosity.dtb
  DTC     arch/arm/boot/dts/microchip/at91-sama5d2_icp.dtb
  DTC     arch/arm/boot/dts/microchip/at91-sama5d2_ptc_ek.dtb
  DTC     arch/arm/boot/dts/microchip/at91-sama5d2_xplained.dtb
  DTC     arch/arm/boot/dts/microchip/at91-sama7g5ek.dtb

[..]

If the building process is successful, the final images can be found under arch/arm/boot/ directory.

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