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x86: Simplify Flash-to-RAM code execution transition

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Move the relocation offset calculation out of assembler and into C. This
also paves the way for the upcoming init sequence simplification by adding
the board_init_f_r flash to RAM transitional function

--
Changes for v2:
 - Added commit message
 - Minor adjustment to new stack address comment
This commit is contained in:
Graeme Russ 2012-01-01 15:06:39 +11:00
parent 74bfbe1ba5
commit f48dd6fc6c
3 changed files with 30 additions and 19 deletions
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22
arch/x86/cpu/start.S
View file

@ -96,32 +96,22 @@ car_init_ret:
movw $0x85, %ax
jmp die
.globl relocate_code
.type relocate_code, @function
relocate_code:
.globl board_init_f_r_trampoline
.type board_init_f_r_trampoline, @function
board_init_f_r_trampoline:
/*
* SDRAM has been initialised, U-Boot code has been copied into
* RAM, BSS has been cleared and relocation adjustments have been
* made. It is now time to jump into the in-RAM copy of U-Boot
*
* %eax = Address of top of stack
* %edx = Address of Global Data
* %ecx = Base address of in-RAM copy of U-Boot
* %eax = Address of top of new stack
*/
/* Setup stack in RAM */
movl %eax, %esp
/* Setup call address of in-RAM copy of board_init_r() */
movl $board_init_r, %ebp
addl (GENERATED_GD_RELOC_OFF)(%edx), %ebp
/* Setup parameters to board_init_r() */
movl %edx, %eax
movl %ecx, %edx
/* Jump to in-RAM copy of board_init_r() */
call *%ebp
/* Re-enter U-Boot by calling board_init_f_r */
call board_init_f_r
die:
hlt

2
arch/x86/include/asm/u-boot-x86.h
View file

@ -61,5 +61,7 @@ u32 isa_map_rom(u32 bus_addr, int size);
int video_bios_init(void);
int video_init(void);
void board_init_f_r_trampoline(ulong) __attribute__ ((noreturn));
void board_init_f_r(void) __attribute__ ((noreturn));
#endif /* _U_BOOT_I386_H_ */

25
arch/x86/lib/board.c
View file

@ -253,10 +253,29 @@ void board_init_f(ulong boot_flags)
gd->flags |= GD_FLG_RELOC;
/* Enter the relocated U-Boot! */
relocate_code(gd->start_addr_sp, gd, gd->relocaddr);
/*
* SDRAM is now initialised, U-Boot has been copied into SDRAM,
* the BSS has been cleared etc. The final stack can now be setup
* in SDRAM. Code execution will continue (momentarily) in Flash,
* but with the stack in SDRAM and Global Data in temporary memory
* (CPU cache)
*/
board_init_f_r_trampoline(gd->start_addr_sp);
/* NOTREACHED - relocate_code() does not return */
/* NOTREACHED - board_init_f_r_trampoline() does not return */
while (1)
;
}
void board_init_f_r(void)
{
/*
* Transfer execution from Flash to RAM by calculating the address
* of the in-RAM copy of board_init_r() and calling it
*/
(board_init_r + gd->reloc_off)(gd, gd->relocaddr);
/* NOTREACHED - board_init_r() does not return */
while (1)
;
}