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>

1 files changed, 35 insertions, 0 deletions

diff --git a/common/spl/spl.c b/common/spl/spl.c
index ded0f30..cd75bbc 100644
--- a/common/spl/spl.c
+++ b/common/spl/spl.c
@@ -281,3 +281,38 @@ void preloader_console_init(void)
 	spl_display_print();
 #endif
 }
+
+/**
+ * spl_relocate_stack_gd() - Relocate stack ready for board_init_r() execution
+ *
+ * Sometimes board_init_f() runs with a stack in SRAM but we want to use SDRAM
+ * for the main board_init_r() execution. This is typically because we need
+ * more stack space for things like the MMC sub-system.
+ *
+ * This function calculates the stack position, copies the global_data into
+ * place and returns the new stack position. The caller is responsible for
+ * setting up the sp register.
+ *
+ * @return new stack location, or 0 to use the same stack
+ */
+ulong spl_relocate_stack_gd(void)
+{
+#ifdef CONFIG_SPL_STACK_R
+	gd_t *new_gd;
+	ulong ptr;
+
+	/* Get stack position: use 8-byte alignment for ABI compliance */
+	ptr = CONFIG_SPL_STACK_R - sizeof(gd_t);
+	ptr &= ~7;
+	new_gd = (gd_t *)ptr;
+	memcpy(new_gd, (void *)gd, sizeof(gd_t));
+	gd = new_gd;
+
+	/* Clear the BSS. */
+	memset(__bss_start, 0, __bss_end - __bss_start);
+
+	return ptr;
+#else
+	return 0;
+#endif
+}