On 10/06/2012 09:11 PM, Dmytro Milinevskyy wrote:
Hi, I'm new to uboot mips port and first decided to try it with qemu.
Welcome. :-)
I've encountered some problems with UART, but I guess that's more qemu issue(lsr reg is not updated when the line is available).
Another issue I faced was code execution after the relocation is done. The address of board_init_r is not computed correctly(it was relative to boot ROM address space/bfc00000). Is it specific to qemu(I don't see the reference here though) or is it a generic mips port issue? Attached patch allows me to proceed with the boot in qemu.
And last - why do we need relocation at all with u-boot? Performance constraints?
Generally, yes. Flash is very often slower than RAM (often 8 bits width vs. 32 bits or more, generally doesn't support bursting, the processor cache may not work with it, etc.).
A side benefit of running out of RAM is that it makes it much easier to write to flash... you don't have to worry about writing to the chip you are executing out of (when you erase/write flash, the chip returns a "programming in progress" status until it is done - that will crash your program if you are running out of that chip).
Thanks, -- dmytro
Best regards, gvb