Launch the latest Linux kernel on Intel Edison

World Day # ArduinoD15 I have prepared material on the configuration and launch of the freshest Linux kernel on the Intel Edison (Arduino Edition) board.

Earlier, I already wrote about how to ensure the loading of the vanilla core on the Intel Galileo board, but now it was the turn for Intel Edison.


For the current day, there is no serial port driver in vanilla cores, which practically makes working with the board impossible. Today, Greg KH, the maintener of the tty subsystem, has approved changes that bring support for the Intel Edison High Speed ​​UART to the core. In reality, changes in the main branch will appear only in version v4.1-rc1.

So let's get started. I want to immediately note that I will not re-describe some of the actions described in the article Launch the vanilla core on Intel Galileo . I also assume that you are using stock firmware based on Yocto.
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Preparing the kernel and file system

First of all, we need a kernel that easily comes from the linux-next repository of the tty subsystem repository (we will need the tty-next branch) :

 mkdir ~/devel cd ~/devel git clone git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git cd ~/devel/linux-next 

You need to make a few minimal edits to the default configuration, namely the arch / x86 / configs / i386_defconfig file . If for some reason you do not want to touch this file, we can easily copy it with the command cp arch/x86/configs/{i386,eds}_defconfig , and in this case use eds_defconfig where the article mentions i386_defconfig .

So, it was (we delete lines from the file):

CONFIG_DRM_I915 = y

It became (add lines to the file):

# CONFIG_DRM_I915 is not set
CONFIG_BACKLIGHT_LCD_SUPPORT = y
CONFIG_USB_XHCI_HCD = y
CONFIG_USB_DWC3 = y
CONFIG_USB_DWC3_GADGET = y
CONFIG_GPIOLIB = y
CONFIG_GPIO_INTEL_MID = y
CONFIG_INTEL_MID_WATCHDOG = y
CONFIG_X86_EXTENDED_PLATFORM = y
CONFIG_X86_INTEL_MID = y
CONFIG_EFI_STUB = y
CONFIG_EARLY_PRINTK_EFI = y
CONFIG_HSU_DMA = y
CONFIG_HSU_DMA_PCI = y
CONFIG_SERIAL_8250_DMA = y
CONFIG_SERIAL_8250_PCI = y

This configuration will immediately include USB, watchdog, GPIO, HSU drivers.

We collect the received:

 make i386_defconfig make -j4 

The result will be the file arch / x86 / boot / bzImage .

The process of preparing the image of the file system is no different from that described earlier with the exception of the output device, which for Intel Edison will be / dev / ttyS2 , and accordingly it is necessary to specify it in the Buildroot configuration parameters:

BR2_TARGET_GENERIC_GETTY_PORT = "ttyS2"

As a result of the assembly, we get the file output / images / rootfs.cpio.bz2 .

Copy results to eMMC

The ~ / devel / linux / arch / x86 / boot / bzImage files obtained during the build process and
~ / devel / buildroot / output / images / rootfs.cpio.bz2 must be copied to our board under the names vmlinuz.efi and initrd, respectively.

We start the board on the stock firmware before switching it to device mode via USB and connecting it with a cable to the computer on which we assembled. After starting the board, the computer will find the USB disk device. It is what we need. We copy our files directly to the root of the connected drive.

Configuring the U-Boot bootloader

The most interesting part of the story is in the magic lines that we need to write to the U-Boot configuration. This is what we need to do.

1. Load the board into the U-Boot command line by pressing any key.
2. Add a few environment variables so that you get the following:
   

     boot_edsboot=zboot 0x100000 0 0x3000000 0x800000 bootargs_edsboot=console=tty1 console=ttyS2,115200n8 rootfstype=ramfs rw bootcmd_edsboot=setenv bootargs ${bootargs_edsboot}; run load_edsboot; run boot_edsboot load_edsboot=load mmc 0:9 0x100000 vmlinuz.efi; load mmc 0:9 0x3000000 initrd 

   
   This is done using the setenv command (detailed examples can be found here ).
3. Save our changes without spoiling the existing ones:
   

     setenv bootcmd_orig ${bootcmd} setenv bootcmd ${bootcmd_edsboot} saveenv 

Now you can load the board, for example, with this command:

 run bootcmd 

or by pressing the reset button.

Accordingly, you can always return to the original configuration by running:

 run bootcmd_orig 

And that is all!