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lightning-boot -- Lightning Platform LF1000 first-stage NAND Flash Bootloader
Andrey Yurovsky <[email protected]>

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# introduction #
################

This bootloader includes basic NAND Flash support (with hardware ECC), LCD 
controller support, and read-only JFFS2 file system support.  A polling UART 
driver is included for debugging purposes.

lightning-boot's task is to:
        0) Bootstrap itself: the hardware loads 0x800 of lightning-boot, and
           lightning-boot then loads the rest.
        1) Enable system VCC and perform some basic CPU initialization.
        2) Read which kernel image to boot and the kernel command line 
           arguments to use.
	3) Read a splash screen into memory, set up the LCD controller, and
           display it.
        4) Fetch that kernel uImage and load it into SDRAM.
        5) Boot the kernel image, with kernel command line arguments passed in.

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# installation #
################

lighting-boot is built using some headers from the Linux kernel.  The 
install.sh script copies these headers and then uses 'make' to build the 
bootloader.  First, configure and build an LF1000 kernel for the board that you
wish to build lightning-boot for (ie: set the TARGET_MACH).  Next, build
lightning-boot:

./install.sh

If you want a clean build, use the '-c' option:

./install.sh -c

If you want UART debugging:

DEBUG=1 ./install.sh

The install script copies lightning-boot.bin to your $TFTP_PATH.

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# Development and Debugging #
#############################

If you want to turn off self-bootstrapping (ex: to test lightning-boot from
u-boot or via JTAG), remove the SELF_BOOTSTRAP option from CFLAGS in the
Makefile and then recompile.  Be aware that SELF_BOOTSTRAP must be enabled for
any build that you intend to write into Flash.

For easier development, a u-boot loading feature is available.  To enable it,
build lightning-boot with UBOOT_SUPPORT defined.  This can be done by providing
the '-u' option, for example:

./install.sh -u

Hold down any button on your development board to have lightning-boot load 
u-boot.bin instead of the kernel.  u-boot.bin must be stored on the first 
kernel partition as a file (just as with the kernel uImage).  This feature can 
be removed by building without the UBOOT_SUPPORT flag defined (the default).

Basic profiling is available in DEBUG mode.  Define DEBUG_STOPWATCH, for
example:

DEBUG=1 DEBUG_STOPWATCH=1 ./install.sh -c

to enable it.  This will turn on stopwatch code provided by the 
db_stopwatch_start() and db_stopwatch_stop() routines.  See the comments in
timer.c for details on the timer 'tick' rate.

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# Other Notes #
###############

See the LinuxDist README for information on variables that should be exported
for the install script.