
Mastering Embedded Linux Programming
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In Chapter 3, All About Bootloaders, I mentioned the need for the bootloader to load kernel binaries and other images from various flash devices and to be able to perform system maintenance tasks such as erasing and reprogramming flash memory. It follows that the bootloader must have the drivers and infrastructure to support read, erase, and write operations on the type of memory you have, whether it be NOR, NAND, or managed. I will use U-Boot in the following example; other bootloaders follow a similar pattern.
U-Boot has drivers for NOR CFI chips in drivers/mtd
and has the commands erase
to erase memory and cp.b
to copy data byte by byte, programming the flash. Suppose that you have NOR flash memory mapped from 0x40000000 to 0x48000000, of which 4MiB starting at 0x40040000 is a kernel image, then you would load a new kernel into flash using these U-Boot commands:
U-Boot# tftpboot 100000 uImage U-Boot# erase 40040000 403fffff...