Contents
How do I stop Autoboot U-Boot?
To stop the automatic booting (autoboot) of the pre-installed kernel, send a character to the serial port by pressing a key from the serial console connected to the target. If U-Boot is stopped, it displays a command line console (also called monitor).
What does U-Boot stand for?
Unterseeboot
Encyclopædia Britannica, Inc. U-boat, German U-boot, abbreviation of Unterseeboot, (“undersea boat”), a German submarine. The destruction of enemy shipping by German U-boats was a spectacular feature of both World Wars I and II.
How are the command line arguments passed to Linux kernel by the U-boot?
In U-Boot, this is supported using the bootargs environment variable. Its contents are automatically passed to the Linux kernel as boot arguments (or “command line” arguments). This allows the use of the same Linux kernel image in a wide range of configurations.
How do I configure U-boot?
To summarize, you need to configure U-Boot for your with the following steps:
- Add your board device tree: arch/arm/dts/.
- Create your own board support directory: board//.
- Add TARGET_ _ in Kconfig.
- Create your board defconfig: defconfig/_defconfig.
Where are u-boot environment variables stored?
SD Card memory
The U-Boot environment is stored in the SD Card memory and is persistent across power or reset cycles. Parameters defined by the U-boot environment variables include: target IP address, target MAC address, location in RAM where a Linux bootable image will be loaded, and many others.
What is Bootcmd?
bootcmd : This variable defines a command string that is automatically executed when the initial countdown is not interrupted. This command is only executed when the variable bootdelay is also defined!
What happens if I run Fw _ setenv in U-Boot?
If the fw_env.config does not point to U-Boot’s env section in Flash, running fw_setenv could corrupt your Flash. Make sure that fw_printenv works properly and does not return a message about “bad CRC” before running fw_setenv .
How to set the bootargs variable in U-Boot?
U-Boot uses its bootargs environment variable as parameter. This variable can be defined statically in U-Boot environment as follow: NAON#setenv bootargs ‘root=/dev/mmcblk0p1 rw console=ttyO0,115200n8 earlyprintk mem=176M vram=46M notifyk.vpssm3_sva=0xBF900000’ NAON#saveenv Saving Environment to SPI Flash…
How is the command line created in U-Boot?
This is more flexible and allow the user to change only a single part of the command line without take care of the whole string. As noted above, commonly the command line is created by U-Boot environment variable substitution and string concatenation.
Where can I Find U-boot environment variables in Linux?
It can be helpful to read and set these variables from Linux as well. The U-Boot distribution has sources for these commands, named fw_printenv and fw_setenv . The Angstrom OE distribution does not build the tools automatically.