[U-Boot] [PATCH 4/5] nios2: initialize stack earlier in startup

[Thomas Chou]

This patch reorders the startup sequence, and initializes stack
earlier. So that we can call external functions after stack
initialized.

We will add OF control and use separated dtb. As dtb is located at
the end of u-boot-dtb.bin image, we will need to relocate it before
zeroing the bss. It will be easier to handle fdt in C than ASM.

Signed-off-by: Thomas Chou <thomas at wytron.com.tw>
---
 arch/nios2/cpu/start.S | 45 ++++++++++++++++++++++-----------------------
 1 file changed, 22 insertions(+), 23 deletions(-)

diff --git a/arch/nios2/cpu/start.S b/arch/nios2/cpu/start.S
index 6af9b4e..dde80f7 100644
--- a/arch/nios2/cpu/start.S
+++ b/arch/nios2/cpu/start.S
@@ -68,7 +68,7 @@ _except_end:
 _cur:	movhi	r5, %hi(_cur - _start)
 	ori	r5, r5, %lo(_cur - _start)
 	sub	r4, r4, r5		/* r4 <- cur _start */
-	mov	r8, r4
+	mov	r8, r4			/* r8 <- cur _start */
 	movhi	r5, %hi(_start)
 	ori	r5, r5, %lo(_start)	/* r5 <- linked _start */
 	beq	r4, r5, 3f
@@ -82,26 +82,34 @@ _cur:	movhi	r5, %hi(_cur - _start)
 	bne	r5, r6, 2b
 3:
 
+	/* JUMP TO RELOC ADDR */
+	movhi	r4, %hi(_reloc)
+	ori	r4, r4, %lo(_reloc)
+	jmp	r4
+_reloc:
+
+	/* STACK INIT -- zero top two words for call back chain. */
+	movhi	sp, %hi(CONFIG_SYS_INIT_SP)
+	ori	sp, sp, %lo(CONFIG_SYS_INIT_SP)
+	addi	sp, sp, -8
+	stw	r0, 0(sp)
+	stw	r0, 4(sp)
+	mov	fp, sp
+
 	/* ZERO BSS/SBSS -- bss and sbss are assumed to be adjacent
 	 * and between __bss_start and __bss_end.
 	 */
-	 movhi	r5, %hi(__bss_start)
-	 ori	r5, r5, %lo(__bss_start)
-	 movhi	r6, %hi(__bss_end)
-	 ori	r6, r6, %lo(__bss_end)
-	 beq	r5, r6, 5f
+	movhi	r5, %hi(__bss_start)
+	ori	r5, r5, %lo(__bss_start)
+	movhi	r6, %hi(__bss_end)
+	ori	r6, r6, %lo(__bss_end)
+	beq	r5, r6, 5f
 
 4:	stwio	r0, 0(r5)
-	 addi	r5, r5, 4
-	 bne	r5, r6, 4b
+	addi	r5, r5, 4
+	bne	r5, r6, 4b
 5:
 
-	/* JUMP TO RELOC ADDR */
-	movhi	r4, %hi(_reloc)
-	ori	r4, r4, %lo(_reloc)
-	jmp	r4
-_reloc:
-
 	/* COPY EXCEPTION TRAMPOLINE -- copy the tramp to the
 	 * exception address. Define CONFIG_ROM_STUBS to prevent
 	 * the copy (e.g. exception in flash or in other
@@ -124,15 +132,6 @@ _reloc:
 7:
 #endif
 
-	/* STACK INIT -- zero top two words for call back chain.
-	 */
-	movhi	sp, %hi(CONFIG_SYS_INIT_SP)
-	ori	sp, sp, %lo(CONFIG_SYS_INIT_SP)
-	addi	sp, sp, -8
-	stw	r0, 0(sp)
-	stw	r0, 4(sp)
-	mov	fp, sp
-
 	/*
 	 * Call board_init_f -- never returns
 	 */
-- 
2.1.4