[U-Boot] [PATCH v2 05/17] x86: Simplify Flash-to-RAM code execution transition

[Graeme Russ]

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

Signed-off-by: Graeme Russ <graeme.russ at gmail.com>
---
Changes for v2:
 - Added commit message
 - Minor adjustment to new stack address comment

 arch/x86/cpu/start.S              |   22 ++++++----------------
 arch/x86/include/asm/u-boot-x86.h |    2 ++
 arch/x86/lib/board.c              |   25 ++++++++++++++++++++++---
 3 files changed, 30 insertions(+), 19 deletions(-)

diff --git a/arch/x86/cpu/start.S b/arch/x86/cpu/start.S
index 6027f54..69a9b2c 100644
--- 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 755f88a..c3d2277 100644
--- 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 f9eb15b..382ada7 100644
--- 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)
 		;
 }
--
1.7.5.2.317.g391b14