[U-Boot] SPL: branching out of start.S

[Marek Vasut <marek.vasut@gmail.com>]

> The way the SPL code is setup right now it only works in the
> CONFIG_NAND_SPL case. The chip I'm working on, the lpc313x, can SPL
> from six different sources. I've implemented the secondary loader code
> in board_init_r in cpu/arm926ejs/lpc313x/spl.c. I needed to modify
> start.S so that the jump to board_init_r works correctly in the SPL
> case.
> 
> Is it possible to merge things further and get rid of this special case?
> 
> #ifdef CONFIG_NAND_SPL
> 	ldr     r0, _nand_boot_ofs
> 	mov	pc, r0
> 
> _nand_boot_ofs:
> 	.word nand_boot
> #else
> 	ldr	r0, _board_init_r_ofs
> 	ldr	r1, _TEXT_BASE
> 	add	lr, r0, r1
> 	add	lr, lr, r9
> 
> ---------------------------------------------------------------------------
> 
> diff --git a/arch/arm/cpu/arm926ejs/start.S
> b/arch/arm/cpu/arm926ejs/start.S index 5e30745..0f97979 100644
> --- a/arch/arm/cpu/arm926ejs/start.S
> +++ b/arch/arm/cpu/arm926ejs/start.S
> @@ -64,6 +64,13 @@ _start:
>         b       reset
>  #endif
>  #ifdef CONFIG_SPL_BUILD
> +#ifdef CONFIG_LPC313x_BOOT_HEADER
> +        .word 0x41676d69        /* image magic number, imgA */
> +        .word 0,0,0,0,0
> +        .word 0x0000000A        /*Plain text no CRC check*/
> +       .word (__initial_boot_image_size)       /* image length */
> +        .word 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
> +#else
>  /* No exception handlers in preloader */
>         ldr     pc, _hang
>         ldr     pc, _hang
> @@ -83,6 +90,7 @@ _hang:
>         .word   0x12345678
>         .word   0x12345678
>         .word   0x12345678
> +#endif
>  #else
>         ldr     pc, _undefined_instruction
>         ldr     pc, _software_interrupt
> @@ -126,7 +134,11 @@ _fiq:
> 
>  .globl _TEXT_BASE
>  _TEXT_BASE:
> +#ifdef CONFIG_SPL_BUILD
> +       .word   CONFIG_SPL_TEXT_BASE
> +#else
>         .word   CONFIG_SYS_TEXT_BASE
> +#endif
> 
>  /*
>   * These are defined in the board-specific linker script.
> @@ -210,6 +222,7 @@ relocate_code:
>  stack_setup:
>         mov     sp, r4
> 
> +       mov     r9, #0x00000000         /* relocation offset starts at zero
> */ adr     r0, _start
>         cmp     r0, r6
>         beq     clear_bss               /* skip relocation */

You can supply your own, separate, start.S for SPL.

M