Boot Process and U-Boot Environment

Owned by Tracy Yang
Nov 28, 2023

Before following the instructions in this section, user must have access to the switch console. User's terminal emulation software has to be configured with the following settings to ensure a successful console connection to the switch:

  • Baud rate: 115200
  • Data bits: 8
  • Stop bits: 1

Modifying U-Boot Parameters

U-Boot (Universal Boot Loader) is an open source, primary boot loader for embedded devices. U-boot is used to package the instructions to boot the operating system kernel of a device. The following example shows the auto boot-up sequence:

U-Boot 1.3.0 (Sep 8 2014 - 16:39:03) 
CPU:   8541, Version: 1.1, (0x80720011)
Core:  E500, Version: 2.4, (0x80200020)
Clock Configuration:
       CPU: 825 MHz, CCB: 330 MHz,
       DDR: 165 MHz, LBC:  41 MHz
L1:    D-cache 32 kB enabled
       I-cache 32 kB enabled
I2C:   ready
DRAM:  Initializing
initdram robin1
initdram robin2
robin before CFG_READ_SPD
robin after CFG_READ_SPD
initdram robin3
    DDR: 512 MB
FLASH: 32 MB
L2 cache 256KB: enabled
In:    serial
Out:   serial
Err:   serial
Net:   TSEC0, TSEC1
IDE:   Bus 0: OK
  Device 0: Model: CF 512MB Firm: 20060911 Ser#: TSS25016070309051750
            Type: Hard Disk
            Capacity: 495.1 MB = 0.4 GB (1014048 x 512)
Hit any key to stop autoboot:  5

To modify the baud rate or other boot parameters, interrupt the boot sequence by hitting any key during auto boot. Once the boot sequence is interrupted, user is at the U-boot shell.

Do not interrupt the default auto boot sequence unless the file system is being fixed or the console port settings are being changed.

The most common commands in U-Boot are:

  • help - Get command line help.
  • printenv - Show all environment variables. The U-Boot environment is a block of memory kept on persistent storage and copied to RAM when U-Boot starts. It stores environment variables used to configure the system.
  • version - Show the U-Boot version.
  • setenv - Set an environment variable.
  • saveenv - Save the modification in the environment memory. 

Use the set and save commands to reset the U-Boot environment variables. In the example below, the baud rate is set to 11520 with the setenv baudrate 115200 command.

=> set baudrate 115200
=> save        
Saving Environment to Flash...
Un-Protected 1 sectors
Erasing Flash...
. done
Erased 1 sectors
Writing to Flash... done
Protected 1 sectors
=> reset

PicOS switches do support Linux shutdown command. To shut down a switch,  after running the “sudo shutdown -h now" command, disconnect the power supply.

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