arm: spl: Allow board_init_r() to run with a larger stack

At present SPL uses a single stack, either CONFIG_SPL_STACK or
CONFIG_SYS_INIT_SP_ADDR. Since some SPL features (such as MMC and
environment) require a lot of stack, some boards set CONFIG_SPL_STACK to
point into SDRAM. They then set up SDRAM very early, before board_init_f(),
so that the larger stack can be used.

This is an abuse of lowlevel_init(). That function should only be used for
essential start-up code which cannot be delayed. An example of a valid use is
when only part of the SPL code is visible/executable, and the SoC must be set
up so that board_init_f() can be reached. It should not be used for SDRAM
init, console init, etc.

Add a CONFIG_SPL_STACK_R option, which allows the stack to be moved to a new
address before board_init_r() is called in SPL.

The expected SPL flow (for CONFIG_SPL_FRAMEWORK) is documented in the README.

Signed-off-by: Simon Glass <sjg@chromium.org>
For version 1:
Acked-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Bo Shen <voice.shen@atmel.com>
Acked-by: Bo Shen <voice.shen@atmel.com>
Acked-by: Heiko Schocher <hs@denx.de>
Tested-by: Heiko Schocher <hs@denx.de>

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/lib/crt0.S b/arch/arm/lib/crt0.S
index 22df3e5..7939ced 100644
--- a/arch/arm/lib/crt0.S
+++ b/arch/arm/lib/crt0.S
@@ -113,7 +113,14 @@
 /* Set up final (full) environment */
 
 	bl	c_runtime_cpu_setup	/* we still call old routine here */
-
+#endif
+#if !defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_FRAMEWORK)
+# ifdef CONFIG_SPL_BUILD
+	/* Use a DRAM stack for the rest of SPL, if requested */
+	bl	spl_relocate_stack_gd
+	cmp	r0, #0
+	movne	sp, r0
+# endif
 	ldr	r0, =__bss_start	/* this is auto-relocated! */
 	ldr	r1, =__bss_end		/* this is auto-relocated! */
 
@@ -124,9 +131,10 @@
 	addlo	r0, r0, #4		/* move to next */
 	blo	clbss_l
 
+#if ! defined(CONFIG_SPL_BUILD)
 	bl coloured_LED_init
 	bl red_led_on
-
+#endif
 	/* call board_init_r(gd_t *id, ulong dest_addr) */
 	mov     r0, r9                  /* gd_t */
 	ldr	r1, [r9, #GD_RELOCADDR]	/* dest_addr */
@@ -134,7 +142,6 @@
 	ldr	pc, =board_init_r	/* this is auto-relocated! */
 
 	/* we should not return here. */
-
 #endif
 
 ENDPROC(_main)