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 now:
Execution starts with start.S. Two main functions can be provided by the
board implementation. The purpose and limitations of each is described below.
After that, the common board_init_r() is called to perform the SPL task.
lowlevel_init():
- purpose: essential init to permit execution to reach board_init_f()
- no global_data, but there is a stack
- must not set up SDRAM or use console
- must only do the bare minimum to allow execution to continue to
board_init_f()
- this is almost never needed
- return normally from this function
board_init_f():
- purpose: set up the machine ready for running board_init_r():
i.e. SDRAM and serial UART
- global_data is available
- preloader_console_init() can be called here in extremis
- stack is in SRAM
- should set up SDRAM, and anything needed to make the UART work
- these is no need to clear BSS, it will be done by crt0.S
- must return normally from this function (don't call board_init_r()
directly)
Here the BSS is cleared. If CONFIG_SPL_STACK_R is defined, then at this point
the stack and global_data are relocated to below that address.
board_init_r():
- purpose: main execution, common code
- global_data is available
- SDRAM is available
- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
points into SDRAM
- preloader_console_init() can be called here - typically this is
done by defining CONFIG_SPL_BOARD_INIT and then supplying a
spl_board_init() function containing this call
- loads U-Boot or (in falcon mode) Linux
Note: This patch is intended to apply over the top of Tom's SPL changes and
this series:
https://patchwork.ozlabs.org/patch/423785/
Signed-off-by: Simon Glass <s...@chromium.org>
---
arch/arm/lib/crt0.S | 13 ++++++++++---
common/spl/spl.c | 35 +++++++++++++++++++++++++++++++++++
doc/README.SPL | 42 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 87 insertions(+), 3 deletions(-)
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 @@ here:
/* 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 @@ clbss_l:cmp r0, r1 /* while not at
end of BSS */
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 @@ clbss_l:cmp r0, r1 /* while not at end of
BSS */
ldr pc, =board_init_r /* this is auto-relocated! */
/* we should not return here. */
-
#endif
ENDPROC(_main)
diff --git a/common/spl/spl.c b/common/spl/spl.c
index 1826c47..78bb279 100644
--- a/common/spl/spl.c
+++ b/common/spl/spl.c
@@ -276,3 +276,38 @@ 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
+}
diff --git a/doc/README.SPL b/doc/README.SPL
index 3ba313c..327d3e2 100644
--- a/doc/README.SPL
+++ b/doc/README.SPL
@@ -95,3 +95,45 @@ cflow will spit out a number of warnings as it does not parse
the config files and picks functions based on #ifdef. Parsing the '.i'
files instead introduces another set of headaches. These warnings are
not usually important to understanding the flow, however.
+
+
+ARM SPL Control Flow
+--------------------
+
+Execution starts with start.S. Two main functions can be provided by the
+board implementation. The purpose and limitations of each is described below.
+After that, the common board_init_r() is called to perform the SPL task.
+
+lowlevel_init():
+ - purpose: essential init to permit execution to reach board_init_f()
+ - no global_data, but there is a stack
+ - must not set up SDRAM or use console
+ - must only do the bare minimum to allow execution to continue to
+ board_init_f()
+ - this is almost never needed
+ - return normally from this function
+
+board_init_f():
+ - purpose: set up the machine ready for running board_init_r():
+ i.e. SDRAM and serial UART
+ - global_data is available
+ - preloader_console_init() can be called here in extremis
+ - stack is in SRAM
+ - should set up SDRAM, and anything needed to make the UART work
+ - these is no need to clear BSS, it will be done by crt0.S
+ - must return normally from this function (don't call board_init_r()
+ directly)
+
+Here the BSS is cleared. If CONFIG_SPL_STACK_R is defined, then at this point
+the stack and global_data are relocated to below that address.
+
+board_init_r():
+ - purpose: main execution, common code
+ - global_data is available
+ - SDRAM is available
+ - stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
+ points into SDRAM
+ - preloader_console_init() can be called here - typically this is
+ done by defining CONFIG_SPL_BOARD_INIT and then supplying a
+ spl_board_init() function containing this call
+ - loads U-Boot or (in falcon mode) Linux
--
2.2.0.rc0.207.ga3a616c
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