[U-Boot] [PATCH v6 4/6] arm: spl: Allow board_init_r() to run with a larger stack
Simon Glass
sjg at chromium.org
Tue Mar 3 16:03:00 CET 2015
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 at chromium.org>
For version 1:
Acked-by: Albert ARIBAUD <albert.u.boot at aribaud.net>
Reviewed-by: Stefan Roese <sr at denx.de>
Tested-by: Bo Shen <voice.shen at atmel.com>
Acked-by: Bo Shen <voice.shen at atmel.com>
Acked-by: Heiko Schocher <hs at denx.de>
Tested-by: Heiko Schocher <hs at denx.de>
---
Changes in v6: None
Changes in v5:
- Rebase to master
Changes in v4:
- Adjust README to mention that lowlevel_init() should have no stack
Changes in v3: None
Changes in v2:
- Move docs to top-level README file and expand them to cover U-Boot proper
- Add Kconfig settings
Kconfig | 18 ++++++++++++++
README | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++
arch/arm/lib/crt0.S | 13 +++++++---
common/spl/spl.c | 35 +++++++++++++++++++++++++++
4 files changed, 132 insertions(+), 3 deletions(-)
diff --git a/Kconfig b/Kconfig
index 91a0618..8de731d 100644
--- a/Kconfig
+++ b/Kconfig
@@ -96,6 +96,24 @@ config SPL
help
If you want to build SPL as well as the normal image, say Y.
+config CONFIG_SPL_STACK_R
+ depends on SPL
+ bool "Enable SDRAM location for SPL stack"
+ help
+ SPL starts off execution in SRAM and thus typically has only a small
+ stack available. Since SPL sets up DRAM while in its board_init_f()
+ function, it is possible for the stack to move there before
+ board_init_r() is reached. This option enables a special SDRAM
+ location for the SPL stack. U-Boot SPL switches to this after
+ board_init_f() completes, and before board_init_r() starts.
+
+config CONFIG_SPL_STACK_R_ADDR
+ depends on CONFIG_SPL_STACK_R
+ hex "SDRAM location for SPL stack"
+ help
+ Specify the address in SDRAM for the SPL stack. This will be set up
+ before board_init_r() is called.
+
config TPL
bool
depends on SPL && SUPPORT_TPL
diff --git a/README b/README
index febefb5..3547ead 100644
--- a/README
+++ b/README
@@ -273,6 +273,75 @@ run some of U-Boot's tests.
See board/sandbox/README.sandbox for more details.
+Board Initialisation Flow:
+--------------------------
+
+This is the intended start-up flow for boards. This should apply for both
+SPL and U-Boot proper (i.e. they both follow the same rules). At present SPL
+mostly uses a separate code path, but the funtion names and roles of each
+function are the same. Some boards or architectures may not conform to this.
+At least most ARM boards which use CONFIG_SPL_FRAMEWORK conform to this.
+
+Execution starts with start.S with three functions called during init after
+that. The purpose and limitations of each is described below.
+
+lowlevel_init():
+ - purpose: essential init to permit execution to reach board_init_f()
+ - no global_data or BSS
+ - there is no stack (ARMv7 may have one but it will soon be removed)
+ - 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
+ - stack is in SRAM
+ - BSS is not available, so you cannot use global/static variables,
+ only stack variables and global_data
+
+ Non-SPL-specific notes:
+ - dram_init() is called to set up DRAM. If already done in SPL this
+ can do nothing
+
+ SPL-specific notes:
+ - you can override the entire board_init_f() function with your own
+ version as needed.
+ - preloader_console_init() can be called here in extremis
+ - 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. For SPL, if CONFIG_SPL_STACK_R is defined, then at
+this point the stack and global_data are relocated to below
+CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
+memory.
+
+board_init_r():
+ - purpose: main execution, common code
+ - global_data is available
+ - SDRAM is available
+ - BSS is available, all static/global variables can be used
+ - execution eventually continues to main_loop()
+
+ Non-SPL-specific notes:
+ - U-Boot is relocated to the top of memory and is now running from
+ there.
+
+ SPL-specific notes:
+ - stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
+ CONFIG_SPL_STACK_R_ADDR 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
+
+
+
Configuration Options:
----------------------
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 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
+}
--
2.2.0.rc0.207.ga3a616c
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