crelooki.blogg.se - U boot source

#U boot source serial
#U boot source full
#U boot source software
#U boot source code

Operating system, kernel size, entry points, etc. This header includes the target architecture, the ZImage is the compressed kernel image wrapped with header info thatĭescribes the kernel. Program and manipulate a wide range of external memory devices as well asĪ helpful aid during custom board bringup. Viewed, modified, and saved using the env print, env set, andĮnv save commands, respectively. These environment variablesĪre stored in the uEnv.txt file on your storage medium or directly inĪ Flash-based memory if configured such. U-Boot environment variables can be configured. Parameters such as boot arguments and the kernel boot command.

#U boot source serial

U-Boot allows for powerful command-based control over the kernel bootĮnvironment via a serial terminal. Process for the next bootloader stage: U-Boot. The SPL has very limited configuration or user interaction,Īnd mainly serves to initialize the external DDR memory and set-up the boot The SPL is theįirst stage of U-Boot, and must be loaded from one of the boot sources into The second stage bootloader is known as the SPL (Secondary Program Loader),īut is sometimes referred to as the MLO (MMC Card Loader). Information on the SYSBOOT pins and associated boot parameters see the expected crystal frequency, bus width of external memory). These pins also set other boot parameters Second stage bootloader is configured by the voltage levels set on theĭevices SYSBOOT pins on startup.

#U boot source code

The list of booting devices that the ROM code will search through for the Stage of bootloader (SPL) as well as loading the actual next stageīootloader code into memory and starting it

Readies the device for next bootloader by checking boot sources for next.

Such as stack setup, configuring the Watchdog Timer (see TRM for details)Īs well as the PLL and system clocks configuration

Configuration of the device and initialization of primary peripherals.

To get an understanding of what exactly the ROM code is doing. The ROM bootloader code is hardcoded into theĭevice and cannot be changed by the user. The first block of code that is automatically run on device start-up orĪfter power-on reset (POR). The first stage bootloader is housed in ROM on the device. There are four distinct bootloader stages:

#U boot source full

Systematically unlock the full functionality of the device so that allĬomplexities of the device are available to the kernel. Of RAM, multiple bootloader stages are needed.

#U boot source software

This section will review the four bootloader software stages that mustīe run before the kernel can be booted and run on the device.Īpplication processors such as the the AM335x are complex pieces of hardware,īut have limited internal RAM (e.g., 128KB). Pointing a program counter to the kernel location and letting the processor Will leverage other files under include/configs, as seen by #includeīooting the Linux kernel on an embedded platform is not as simple as simply And please note that the main config file To find these read the ‘boards.cfg’ file and look for Here as the community has additional build targets that are not Note that not all possible build targets for a given platform are listed $ make CROSS_COMPILE=arm-linux-gnueabihf- O=am335x_evm $ make CROSS_COMPILE=arm-linux-gnueabihf- O=am335x_evm am335x_evm_defconfig # Use 'am335x_evm' and 'AM335x GP EVM' in this example

Use the following table to determine what defconfig to use to configure However first configure the build for the board you are working with. Building of both u-boot and SPL is done at the same time.