[U-Boot,v2,1/3] arm: Allow lr to be saved by board code

The link register value can be required on some boards (e.g. FEL mode on
sunxi) so use a branch instruction to jump to save_boot_params() instead
of a branch link.

This requires a branch back to save_boot_params_ret so adjust the users
to deal with this. For exynos just drop the function since it doesn't
do anything.

Signed-off-by: Simon Glass <sjg@chromium.org>
---

Changes in v2:
- Change save_boot_params() to not use lr for return
- Fix up existing save_boot_params() functions for new API

 arch/arm/cpu/armv7/exynos/spl_boot.c           |  1 -
 arch/arm/cpu/armv7/omap-common/lowlevel_init.S |  2 +-
 arch/arm/cpu/armv7/omap3/lowlevel_init.S       |  2 +-
 arch/arm/cpu/armv7/start.S                     |  7 +++++--
 arch/arm/include/asm/system.h                  | 15 +++++++++++++++
 board/nokia/rx51/lowlevel_init.S               |  3 ++-
 6 files changed, 24 insertions(+), 6 deletions(-)

On Sat,  7 Feb 2015 10:47:28 -0700
Simon Glass <sjg@chromium.org> wrote:

> The link register value can be required on some boards (e.g. FEL mode on
> sunxi) so use a branch instruction to jump to save_boot_params() instead
> of a branch link.
> 
> This requires a branch back to save_boot_params_ret so adjust the users
> to deal with this. For exynos just drop the function since it doesn't
> do anything.
> 
> Signed-off-by: Simon Glass <sjg@chromium.org>
> ---
> 
> Changes in v2:
> - Change save_boot_params() to not use lr for return
> - Fix up existing save_boot_params() functions for new API
> 
>  arch/arm/cpu/armv7/exynos/spl_boot.c           |  1 -
>  arch/arm/cpu/armv7/omap-common/lowlevel_init.S |  2 +-
>  arch/arm/cpu/armv7/omap3/lowlevel_init.S       |  2 +-
>  arch/arm/cpu/armv7/start.S                     |  7 +++++--
>  arch/arm/include/asm/system.h                  | 15 +++++++++++++++
>  board/nokia/rx51/lowlevel_init.S               |  3 ++-
>  6 files changed, 24 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/cpu/armv7/exynos/spl_boot.c b/arch/arm/cpu/armv7/exynos/spl_boot.c
> index bc237c9..c7f943e 100644
> --- a/arch/arm/cpu/armv7/exynos/spl_boot.c
> +++ b/arch/arm/cpu/armv7/exynos/spl_boot.c
> @@ -309,4 +309,3 @@ void board_init_r(gd_t *id, ulong dest_addr)
>  	while (1)
>  		;
>  }
> -void save_boot_params(u32 r0, u32 r1, u32 r2, u32 r3) {}
> diff --git a/arch/arm/cpu/armv7/omap-common/lowlevel_init.S b/arch/arm/cpu/armv7/omap-common/lowlevel_init.S
> index 86c0e42..e19c7ae 100644
> --- a/arch/arm/cpu/armv7/omap-common/lowlevel_init.S
> +++ b/arch/arm/cpu/armv7/omap-common/lowlevel_init.S
> @@ -19,7 +19,7 @@
>  ENTRY(save_boot_params)
>  	ldr	r1, =OMAP_SRAM_SCRATCH_BOOT_PARAMS
>  	str	r0, [r1]
> -	bx	lr
> +	b	save_boot_params_ret
>  ENDPROC(save_boot_params)
>  
>  ENTRY(set_pl310_ctrl_reg)
> diff --git a/arch/arm/cpu/armv7/omap3/lowlevel_init.S b/arch/arm/cpu/armv7/omap3/lowlevel_init.S
> index 78577b1..80cb263 100644
> --- a/arch/arm/cpu/armv7/omap3/lowlevel_init.S
> +++ b/arch/arm/cpu/armv7/omap3/lowlevel_init.S
> @@ -23,7 +23,7 @@ ENTRY(save_boot_params)
>  	ldr	r5, [r0, #0x4]
>  	and	r5, r5, #0xff
>  	str	r5, [r4]
> -	bx	lr
> +	b	save_boot_params_ret
>  ENDPROC(save_boot_params)
>  #endif
>  
> diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
> index 70048c1..9b49ece 100644
> --- a/arch/arm/cpu/armv7/start.S
> +++ b/arch/arm/cpu/armv7/start.S
> @@ -31,9 +31,12 @@
>   *************************************************************************/
>  
>  	.globl	reset
> +	.globl	save_boot_params_ret
>  
>  reset:
> -	bl	save_boot_params
> +	/* Allow the board to save important registers */
> +	b	save_boot_params
> +save_boot_params_ret:
>  	/*
>  	 * disable interrupts (FIQ and IRQ), also set the cpu to SVC32 mode,
>  	 * except if in HYP mode already
> @@ -96,7 +99,7 @@ ENDPROC(c_runtime_cpu_setup)
>   *
>   *************************************************************************/
>  ENTRY(save_boot_params)
> -	bx	lr			@ back to my caller
> +	b	save_boot_params_ret		@ back to my caller
>  ENDPROC(save_boot_params)
>  	.weak	save_boot_params
>  
> diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
> index 89f2294..7820486 100644
> --- a/arch/arm/include/asm/system.h
> +++ b/arch/arm/include/asm/system.h
> @@ -142,6 +142,21 @@ void flush_l3_cache(void);
>  
>  #ifndef __ASSEMBLY__
>  
> +/**
> + * save_boot_params() - Save boot parameters before starting reset sequence
> + *
> + * If you provide this function it will be called immediately U-Boot starts,
> + * both for SPL and U-Boot proper.
> + *
> + * All registers are unchanged from U-Boot entry. No registers need be
> + * preserved.
> + *
> + * This is not a normal C function. There is no stack. Return by branching to
> + * save_boot_params_ret.
> + *
> + * void save_boot_params(u32 r0, u32 r1, u32 r2, u32 r3);
> + */
> +
>  #define isb() __asm__ __volatile__ ("" : : : "memory")
>  
>  #define nop() __asm__ __volatile__("mov\tr0,r0\t@ nop\n\t");
> diff --git a/board/nokia/rx51/lowlevel_init.S b/board/nokia/rx51/lowlevel_init.S
> index e252909..9d4ea1b 100644
> --- a/board/nokia/rx51/lowlevel_init.S
> +++ b/board/nokia/rx51/lowlevel_init.S
> @@ -37,7 +37,8 @@ ih_magic:		/* IH_MAGIC in big endian from include/image.h */
>  
>  .global save_boot_params
>  save_boot_params:
> -
> +	/* Get return address */
> +	ldr	lr, =save_boot_params_ret
>  
>  /* Copy valid attached kernel to address KERNEL_ADDRESS */
>  

Acked-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>