[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 12:04:16PM -0700, Simon Glass wrote:
> Hi Tom,
> 
> On 3 March 2015 at 10:49, Tom Rini <trini at konsulko.com> wrote:
> > 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.
> 
> OK I'll have to test more. What sort of problem should i see?

We hang on entering env_reloc_spec() which is what puts some big sized
variables on the stack.

> The return value from spl_relocate_stack_gd() should be shoved into
> sp. Does that not happen?

It doesn't appear to be.  I hadn't broken out the BBB with JTAG tho.

-- 
Tom
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