[U-Boot] [PATCH] arm: Tegra2: Fix ELDK42 gcc failure with inline asm stack pointer load

[Simon Glass]

Hi Tom,

On Feb 16, 2012 11:45 AM, "Tom Warren" <twarren.nvidia at gmail.com> wrote:
>
> The 4.2.2 gcc in the ELDK42 release doesn't like the direct SP
> load using a constant in tegra2_start. Break it up into 4 loads
> using mov & orr.
>
> Tested on my Seaboard T20-A03, U-Boot loads and runs OK. Also
> compiled all tegra2 builds with both gcc 4.2.2 and 4.4.1 OK.
>
> Signed-off-by: Tom Warren <twarren at nvidia.com>
> ---
>  arch/arm/cpu/armv7/tegra2/ap20.c |   25 ++++++++++++++++++++-----
>  1 files changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm/cpu/armv7/tegra2/ap20.c
b/arch/arm/cpu/armv7/tegra2/ap20.c
> index 4c44bb3..d2bc0d5 100644
> --- a/arch/arm/cpu/armv7/tegra2/ap20.c
> +++ b/arch/arm/cpu/armv7/tegra2/ap20.c
> @@ -298,11 +298,26 @@ void tegra2_start(void)
>                writel(0xC0, &pmt->pmt_cfg_ctl);
>
>                /*
> -               * If we are ARM7 - give it a different stack. We are
about to
> -               * start up the A9 which will want to use this one.
> -               */
> -               asm volatile("ldr       sp, =%c0\n"
> -                       : : "i"(AVP_EARLY_BOOT_STACK_LIMIT));
> +                * If we are ARM7 - give it a different stack. We are
about to
> +                * start up the A9 which will want to use this one.
> +                */
> +               /*
> +                * Note that the 'ldr sp,CONSTANT' version, below, doesn't
> +                * work on gcc 4.2.2 (ELDK42), but does on gcc 4.4.1 and
above.
> +                * The work-around is to use the (ugly) 4-pass mov/orr
below.
> +                *
> +                * asm volatile("ldr    sp, =%c0\n" : :
> +                *      "i"(AVP_EARLY_BOOT_STACK_LIMIT));
> +                */
> +
> +               asm volatile("mov       sp, %0"
> +                       : : "i"(AVP_EARLY_BOOT_STACK_LIMIT & 0xFF));
> +               asm volatile("orr       sp, %0"
> +                       : : "i"(AVP_EARLY_BOOT_STACK_LIMIT & 0xFF00));
> +               asm volatile("orr       sp, %0"
> +                       : : "i"(AVP_EARLY_BOOT_STACK_LIMIT & 0xFF0000));
> +               asm volatile("orr       sp, %0"
> +                       : : "i"(AVP_EARLY_BOOT_STACK_LIMIT & 0xFF000000));

Can we combine these into one asm with 4 parameters?

>
>                start_cpu((u32)_start);
>                halt_avp();
> --
> 1.7.7.1
>
Regards,
Simon