x86: Simplify Flash-to-RAM code execution transition

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

diff --git a/arch/x86/cpu/start.S b/arch/x86/cpu/start.S
index 6027f54186bf711088a02256263715ae75776e58..69a9b2cddcf7def542992bda5f6426fc396c8da8 100644 (file)
--- a/arch/x86/cpu/start.S
+++ b/arch/x86/cpu/start.S
@@ -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

diff --git a/arch/x86/include/asm/u-boot-x86.h b/arch/x86/include/asm/u-boot-x86.h
index 755f88af04823a4688f767d9d455633ad11008a6..c3d2277834e4b7b3c9cea1131e4f90f793a3d1bd 100644 (file)
--- a/arch/x86/include/asm/u-boot-x86.h
+++ b/arch/x86/include/asm/u-boot-x86.h
@@ -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_ */

diff --git a/arch/x86/lib/board.c b/arch/x86/lib/board.c
index f9eb15bed365457fd95ee2356a9ca34a9830cf97..382ada784bca4bbe10296da6d9c166f78ab138cd 100644 (file)
--- a/arch/x86/lib/board.c
+++ b/arch/x86/lib/board.c
@@ -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 - 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 - relocate_code() does not return */
+       /* NOTREACHED - board_init_r() does not return */
        while (1)
                ;
 }