--- Wolfgang Denk wd@denx.de wrote:
In message 20040622013446.79298.qmail@web20730.mail.yahoo.com you wrote:
Can u-boot run on top of another bootloader? The board I'm working on
has a
proprietary boot loader. I cannot totally abandon this bootloader
because
the vendor is unwilling to disclose some critical details of the board.
So
I'm thinking of putting u-boot on top of it. Is this idea feasible?
It is possible. Basicly the same modifications need to be made like when attempting to boot from RAM.
What I'm planning to do is as follows. The board's processor is MPC8245. 1. Put u-boot at 0xFFE00000; 2. After power-on the proprietary bootloader starts and initializes the system. 3. On the bootloader execute 'go 0xFFE00000' to load u-boot. u-boot is going to initialize the system again except the proprietary part - CPLD programming.
At the very beginning u-boot is executed from flash. That's why there are some functions with postfix xxx_f(). Since the system has been initialized by the original bootloader, is it possible to skip this step and to copy the necessary part of u-boot to RAM and then to execute it from RAM?
Since it's an MPC8245 board, I use SL8245 as an example. I'm not sure how to configure those IBATs and DBATs. I dumped these registers from BDI2000 but these values just don't make sense to me. For example, the dumped IBAT0U and IBAT0L are ibat0u : 0x1fa4093d ibat0l : 0x4cf40039
#define CFG_IBAT0L (CFG_SDRAM_BASE | BATL_PP_10 | BATL_MEMCOHERENCE) #define CFG_IBAT0U (CFG_SDRAM_BASE | BATU_BL_256M | BATU_VS | BATU_VP) But from the configuration in the hearder file, they should be 0x00000012 and 0x00001FFF.
What are these four pairs of IBAT for? Each one for a specific range of memory space?
I did built an image and put it at 0xFFE00000. However it cannot step forward from the very first instruction. (gdb) c Continuing.
Program received signal SIGSTOP, Stopped (signal) 0xffe00000 in ?? () at /code/u-boot-1.1.1/cpu/mpc824x/start.S:98 98 _start: (gdb)
Why?
Thank you very much, -Shawn.
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