[U-Boot] [PATCH v3] arm64: arm: implement a boot header capability

[Tom Rini]

On Mon, May 30, 2016 at 09:51:22AM -0700, Steve Rae wrote:

> From: Andre Przywara <andre.przywara at arm.com>
> 
> Some SPL loaders (like Allwinner's boot0, and Broadcom's boot0)
> require a header before the actual U-Boot binary to both check its
> validity and to find other data to load. Sometimes this header may
> only be a few bytes of information, and sometimes this might simply
> be space that needs to be reserved for a post-processing tool.
> 
> Introduce a config option to allow assembler preprocessor commands
> to be inserted into the code at the appropriate location; typical
> preprocessor commands might be:
>   .space 1000
>   .word 0x12345678
> etc.
> Please note that the current code:
>   start.S (arm64) and
>   vectors.S (arm)
> already jumps over some portion of data already, so this option basically
> just increases the size of this region (and the resulting binary).
> 
> For use with Allwinner's boot0 blob there is a tool called boot0img[1],
> which fills the header to allow booting A64 based boards.
> For the Pine64 we need a 1536 byte header (including the branch
> instruction) at the moment, so we add this to the defconfig.
> 
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> Signed-off-by: Steve Rae <srae at broadcom.com>

I think this is a step in the right direction.

[snip]
> diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
> index e933021..9202889 100644
> --- a/arch/arm/cpu/armv8/start.S
> +++ b/arch/arm/cpu/armv8/start.S
> @@ -21,6 +21,10 @@
>  _start:
>  	b	reset
>  
> +#ifdef CONFIG_BOOT0_CODE
> +CONFIG_BOOT0_CODE
> +#endif
> +
>  	.align 3

I don't like adding things to the CONFIG name space that we can't
control the contents of via Kconfig.  So I think we need to change the
BOOT0_CODE portion to something like ARMV8_SOC_BOOT0_HOOK.  And if
there's some part of the ARMv8 docs we can reference that explains why
it's boot0 and at least 2 different SoCs have done this, we can use a
better name here.

Then..
> diff --git a/board/sunxi/Kconfig b/board/sunxi/Kconfig
> index c1ae6f5..d2678c9 100644
> --- a/board/sunxi/Kconfig
> +++ b/board/sunxi/Kconfig
> @@ -15,6 +15,13 @@ config SUNXI_GEN_SUN6I
>  	separate ahb reset control registers, custom pmic bus, new style
>  	watchdog, etc.
>  
> +config SUNXI_BOOT0
> +	bool "prepare for boot0 header"
> +	---help---
> +	If U-Boot is loaded from the Allwinner provided boot0 blob, it
> +	expects a header area filled with magic values.
> +	This option will add some space at the beginning of the image to
> +	let a tool later on fill in this header with sensible data.

This becomes something like ENABLE_ARMV8_SOC_BOOT0_HOOK and generic the
text a bit more here and mention the Allwinner and Broadcom examples.

> diff --git a/include/configs/bcm28155_ap.h b/include/configs/bcm28155_ap.h
> index 889e5db..515552b 100644
> --- a/include/configs/bcm28155_ap.h
> +++ b/include/configs/bcm28155_ap.h
> @@ -137,4 +137,8 @@
>  #define CONFIG_USB_GADGET_BCM_UDC_OTG_PHY
>  #define CONFIG_USBID_ADDR		0x34052c46
>  
> +#define CONFIG_BOOT0_CODE	\
> +	.word	0xbabeface;	\
> +	.word	_end - _start
> +

Then this goes into arch/arm/include/asm/arch-bcm281xx/boot0.h or
similar?

>  #endif /* __BCM28155_AP_H */
> diff --git a/include/configs/sun50i.h b/include/configs/sun50i.h
> index 0fdb4c7..fe9624b 100644
> --- a/include/configs/sun50i.h
> +++ b/include/configs/sun50i.h
> @@ -17,6 +17,11 @@
>  #define GICD_BASE		0x1c81000
>  #define GICC_BASE		0x1c82000
>  
> +#ifdef CONFIG_SUNXI_BOOT0
> +#define CONFIG_BOOT0_CODE	\
> +	.space	1532
> +#endif

and .../arch-sunxi/boot0.h

-- 
Tom
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