![]() ![]() Download the sources and decompress the archive into a working directory.Cross Toolchain - available from Timesys through the Factory or Timesys Repository.U-Boot sources - available in the Timesys Repository, through the Factory, or from Denx U-Boot FTP.If you have difficulty building U-Boot for your platform, please consult LinuxLink Support to see if the given port is tested and supported. There are some ports of U-Boot that can only be built using very specific toolchains. Important Note: U-Boot is not necessarily built by Timesys for every board. The following document provides the instructions needed to build U-Boot for a generic board. It only takes a cross-toolchain and a source tree to build a statically-linked binary. Once that is done, you actually pass the device path, not an Address into the kernel.U-boot is extremely easy to build. If it is a persistant filesystem (ext4) then U-boot needs to know how to process the partition map. If it is an initramfs, you get to define where it is stored in raw NAND. If the rootfs is separate, you'll need to know what type of filesystem it is. Obviously your kernel should be able to fit into your memory, and you may need to make sure you are not overwriting other components (rootfs, device tree) when the kernel decompresses itself.Ĥ) Either option exists and is valid. This is typically a job of the kernel itself for legacy reasons. U-boot does not decompress the kernel as its is booting. U-boot then will need the proper LOADADDR for the board/chip you are working with. The job of this SPL is execute out of processor SRAM and to initialize the system DRAM so it is then usable to load the full U-boot executable. U-boot has it's SPL (secondary program loader) feature to do this. The reference manual chapter on booting will tell you.ģ) Often, uboot cannot just "get inside RAM." This has to be done with a first stage bootloader. NOR might be 0x1000, NAND 0x4000 for example. For example, you might be able to boot from memory mapped NOR, NAND, etc. If rootfs is an seprate entity lying on NAND then how will kernel come to know from which address on NAND the rootfs is lying ?ġ) typically there will be an offset for each bootable interface defined in the reference manual. So to defining LOADADDR (uncompressed image address) do we have to take into consideration the space for (uboot itself + compressed uImage to be loaded into RAM) ?įOr uImage how we use to define the LOADADDR ?Ĥ> Do linux uImage have rootfs embedded inside it or it is an seprate entity ? How the RESET vector is specified for 32 bit ARM MCU as it have many diffrent type of external memory interfaces connected to it.ģ> In case of 32 bit ARM MCU, first Uboot will get inside RAM then it will load the compressed uimage in RAM then uboot will decompress the uIMage to LOADADDR. How wil our 32 bit ARM MCU will know from which address place on NAND to fetch the Uboot from ?Īnd on which address in RAM to load the Uboot ?Ģ> In 8-bit MCU like AVR RESET vector address is 0x0000 and is in the inbuild FLASH memory. Now i have few questions from my side :-ġ> 32 bit ARM MCU have many external memory interfaces like DRAM & NAND or NOR flash connected to it. A partition for the kernel (here goes uImage.bin).A small partition where uboot saves its environment variables.A partition for the bootloader (here goes uboot.bin).Usually, in embedded systems the NAND flash is partitioned in four parts:. ![]()
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