[U-Boot] [PATCH v6 4/6] arm: spl: Allow board_init_r() to run with a larger stack

[Tom Rini]

On Tue, Mar 03, 2015 at 08:03:00AM -0700, Simon Glass wrote:

> 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(-)
[snip]
> 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
> +}

All of this _does_ move gd into where CONFIG_SPL_STACK_R points.  It
does _not_ move the stack itself into where CONFIG_SPL_STACK_R points so
the big use case (am335x_boneblack for example where
CONFIG_SPL_ENV_SUPPORT is set) doesn't work and blows up as we overflow
the area for stack.

-- 
Tom
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