Timesys Getting Started Guide for Freescale i.MX 7Dual SABRE board


Contents

Introduction

This document will describe in detail the procedures for booting a Linux kernel image and mounting a root file system from an SD Card on the Freescale i.MX7D SABRE SDB.

Prerequisites

Host Requirements

To properly boot a board using software from Timesys, your host machine must meet the following requirements:

  • Modern GNU/Linux Distribution. While you can use nearly any modern Linux distribution released in the last 24 months, Timesys recommends one of the following:
    • Ubuntu (Most recent release or LTS)
    • Fedora (Most recent release)
  • An internet connection on the Development Host.
  • Root or sudo permission on the Development Host.
  • A copy of the Linux Kernel (uImage) and Root File System (rootfs.tar.gz) for the Target Board downloaded from Factory. These are found in the output directory of your online build, or in the directory build_armv7l-timesys-linux-<libc>/images/ on the command line.
  • If you are booting your root file system over the network, you will need two network cards installed and configured in the Development Host. One to communicate normally with your LAN/WAN while installing host packages, the other to communicate solely with the target board.
  • An available serial port on your Development Host.

Target Requirements

To boot the Freescale i.MX7D SABRE SDBusing NFS (network filesystem), you will need the following items:

  • Freescale i.MX7D SABRE SDB
  • 5V Power Supply
  • RS232 Serial Cable
  • Ethernet Crossover Cable or Ethernet hub/switch and Ethernet Patch Cables

Once you have all of the necessary components, you should perform the following steps:

  1. Connect the UART port of the i.MX7D SABRE SDB board to the serial port of your workstation using the RS232 serial cable.
  2. If you are using a cross-over cable, connect the Ethernet port of the i.MX7D SABRE SDB board to the second Ethernet port of your workstation.
  3. If you are using an Ethernet hub or switch, connect the debug board to the hub with a straight-through Ethernet cable, then connect the hub to the second Ethernet port of your workstation.
  4. Connect the power supply to your board.

Preparing the Target

Configuring Serial Communication

The i.MX7D SABRE SDB uses a serial debug port to communicate with the host machine. The commands discussed in this section are meant to be performed by a privileged user account. This requires the root login or prepending each command with sudo.

Using Minicom

  1. Start minicom on your host machine in configuration mode. As root:

    # minicom -o -s -w

  2. A menu of configuration should appear. Use the Down-arrow key to scroll down and select the Serial port setup option, and press Enter.
  3. Verify that the listed serial port is the same one that is connected to the target board. If it is not, press A, and enter the correct device. This is /dev/ttyS0 on most Linux distributions.
  4. Set the Bps/Par/Bits option by pressing the letter E and using the next menu to set the appropriate values. You press the key that corresponds to the value 115200, then press Enter.
  5. Set Hardware flow control to No using the F key.
  6. Set Software flow control to No using the G key.
  7. Press Enter to return to the main configuration menu, and then press Esc to exit this menu.
  8. Reset the board, and wait for a moment. If you do not see output from the board, press Enter several times until you see the prompt. If you do not see any output from the board, and have verified that the serial terminal connection is setup correctly, contact your board vendor.

TIP: If you experience an error similar to Device /dev/ttyS0 is locked when starting minicom, it usually means that another process is using the serial port (which is usually another instance of minicom). You can find the process that is currently using the serial port by executing the following:

# fuser /dev/ttyS0
/dev/ttyS0:         28358

# ps 28358
  PID TTY      STAT  TIME COMMAND
  28923 pts/0    S+    0:00 minicom

This process can also be killed directly with fuser as root. Please use this command with caution:

# fuser -k /dev/ttyS0

Using GNU Screen

To quickly connect to a board using Gnu Screen, execute the following:

# screen /dev/ttyS0 115200

For more information about using screen, please consult the man page, or view the manual online at http://www.gnu.org/software/screen/manual/screen.html

Preparing the Secure Digital Card

The i.MX7D SABRE SDB boots from an SD card. Some kits may be shipped with one that contains a sample kernel and RFS preloaded. We will be replacing these with the kernel and RFS from Factory. If you are using a blank SD card or have trouble replacing the software on the preloaded one, see Partitioning the SD Card. Otherwise, skip directly to Writing Boot Files to the SD Card.

Before you begin, you should determine the name of your SD card on your host system. To do so:

  1. Connect the SD card to your host system. Many modern systems have SD card slots on the case, or you can purchase a USB SD Card Reader for around $15 US.
  2. Determine the device name of the SD Card. This can be done using dmesg. In the following example, the device is /dev/sdX, which contains one partition sdX1.

    $ dmesg | tail
    [88050.184080] sd 4:0:0:0: [sdX] 1990656 512-byte hardware sectors: (1.01 GB/972 MiB)
    [88050.184821] sd 4:0:0:0: [sdX] Write Protect is off
    [88050.184824] sd 4:0:0:0: [sdX] Mode Sense: 03 00 00 00
    [88050.184827] sd 4:0:0:0: [sdX] Assuming drive cache: write through
    [88050.185575] sd 4:0:0:0: [sdX] 1990656 512-byte hardware sectors: (1.01 GB/972 MiB)
    [88050.186323] sd 4:0:0:0: [sdX] Write Protect is off
    [88050.186325] sd 4:0:0:0: [sdX] Mode Sense: 03 00 00 00
    [88050.186327] sd 4:0:0:0: [sdX] Assuming drive cache: write through
    [88050.186330]  sdX: sdX1

Partitioning the SD card

If you want to use a different SD card or its contents become corrupted, you can use the fdisk tool to create a single Linux partition on your SD card. Please note that all data on the card will be lost upon completion of these steps.
  1. Unmount the partition if it was automounted by using the umount command.
    $ umount /dev/sdX1
  2. As root, run the fdisk utility on the drive.
    $ sudo fdisk /dev/sdX
  3. In fdisk, Delete the existing partition table and create a new one using the o command.
    Command (m for help): o
    Building a new DOS disklabel with disk identifier 0x8b025602.
    Changes will remain in memory only, until you decide to write them.
    After that, of course, the previous content won't be recoverable.
  4. Create a new primary partition using the n command. You will need to leave space for the U-Boot image before the start of the first partition. 2048 should be sufficient.

    Command (m for help): n
    Partition type:
       p   primary (0 primary, 0 extended, 4 free)
       e   extended
    Select (default p): p
    Partition number (1-4, default 1): 1
    First sector (2048-30679039, default 2048): 2048
    Last sector, +sectors or +sizeK,M,G (2048-30679039, default 30679039):
    Using default value 30679039

  5. Verify that the partition table is correct by using the p command. It should look similar to the following:

    Command (m for help): p                                                         
                                                                                    
    Disk /dev/sdX: 15.7 GB, 15707668480 bytes
    64 heads, 32 sectors/track, 14980 cylinders, total 30679040 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk identifier: 0x6eaae8f8

       Device Boot      Start         End      Blocks   Id  System
    /dev/sdX1            2048    30679039    14773960   83  Linux

  6. This step will destroy all data on the SD Card - Write the partition table to the card using the w command.

    Command (m for help): w
    The partition table has been altered!

    Calling ioctl() to re-read partition table.

    WARNING: If you have created or modified any DOS 6.x
    partitions, please see the fdisk manual page for additional
    information.
    Syncing disks.

  7. Format the first partition of the SD card with the ext4 filesystem using the mkfs.ext4 tool.

    $ sudo /sbin/mkfs.ext4 -L rfs /dev/sdX1

Writing Boot Files to the SD Card

  1. Mount the partition. You can remove and reinsert the card to trigger the automount, or you can use the mount command to mount the partition to an arbitrary location.

    $ sudo mount /dev/sdX1 /media/rfs

  2. Copy U-Boot u-boot.imx to the SD card:

    $ sudo dd if=u-boot.imx of=/dev/sdX bs=512 seek=2
    841+1 records in
    841+1 records out
    430824 bytes (431 kB) copied, 0.0669761 s, 6.4 MB/s

  3. As root, extract the rootfs.tar.gz archive to the card.

    $ sudo tar xzf rootfs.tar.gz -C /media/rfs

  4. If you have included the kernel image in your rootfs, this next step is not necessary As root, create the boot directory on the RFS partition of the card.

    $ sudo mkdir /media/rfs/boot

  5. As root, copy the uImage file, uImage, to the boot directory on the RFS partition of the card.

    $ sudo cp uImage /media/rfs/boot/

  6. If using a 3.10 or newer kernel, you will need to copy the Device Tree Blob file, i.MX7D_SABRE_SDB.dtb, to the boot directory on the RFS partition of the card.

    $ sudo cp i.MX7D_SABRE_SDB.dtb /media/rfs/boot/

  7. Unmount the card before removing it from the Development Host. Then place the card in the SD3 slot on the i.MX7D SABRE SDB.

    $ sudo umount /dev/sdX*

  8. Remove the SD Card from the host machine, and insert it into the SD Card slot J6 on the target board. You should hear the card 'click' into place.

Preparing the Host

No additional host setup is required to boot from SD.

Booting the Board

Set Environment Variables

You must set a few environment variables in order to boot the board from the SD card. This is done with the setenv and saveenv commands in U-Boot.

On the target, set the following environment variables:

Variable Value
bootargs console=ttymxc0,115200 ip=dhcp root=/dev/nfs rw
load_kernel ext4load mmc :1 80800000 boot/uImage-4.9-ts-armv7l
load_dtb ext4load mmc :1 83000000 boot/i.MX7D_SABRE_SDB.dtb
bootcmd mmc rescan\; run load_kernel load_dtb\; bootm 80800000 - 83000000

Example

> setenv bootargs console=ttymxc0,115200 ip=dhcp root=/dev/nfs rw
> setenv load_kernel ext4load mmc :1 80800000 boot/uImage-4.9-ts-armv7l
> setenv load_dtb ext4load mmc :1 83000000 boot/i.MX7D_SABRE_SDB.dtb
> setenv bootcmd mmc rescan\; run load_kernel load_dtb\; bootm 80800000 - 83000000
> saveenv

Load The Kernel

You can use the mmc subsystem to load the kernel from the SD card.

Example

> mmc rescan
> ext4load mmc :1 80800000 boot/uImage-4.9-ts-armv7l
reading boot/uImage-4.9-ts-armv7l

3008612 bytes read

Load The Device Tree

You can use the mmc subsystem to load the device tree file (dtb) from the SD card.

Example

> mmc rescan
> ext4load mmc :1 83000000 boot/i.MX7D_SABRE_SDB.dtb
reading boot/i.MX7D_SABRE_SDB.dtb

24612 bytes read

Boot the Kernel

The bootm command is used to boot the kernel. It loads the file that was previously loaded using the ext4load command.

Example

> bootm 80800000 - 83000000
## Booting kernel from Legacy Image at 80800000 ..
   Image Name:   Linux-4.9-ts-armv7l
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    3008548 Bytes =  2.9 MB
   Load Address: 80008000
   Entry Point:  80008000
   Verifying Checksum ... OK
   Loading Kernel Image ... OK
## Flattened Device Tree blob at 83000000
   Booting using the fdt blob at 83000000
   Loading Kernel Image ... OK
OK

Additional Information

Factory Documentation