[U-Boot] [PATCH v2 1/3] sunxi: (mksunxiboot) signature to indicate "sunxi" SPL variant

[Siarhei Siamashka <siarhei.siamashka@gmail.com>]

On Mon, 14 Sep 2015 15:15:28 +0200
Bernhard Nortmann <bernhard.nortmann@web.de> wrote:

> This patch follows up on a discussion of ways to improve support
> for the sunxi FEL ("USB boot") mechanism, especially with regard
> to boot scripts, see:
> https://groups.google.com/d/msg/linux-sunxi/wBEGUoLNRro/rHGq6nSYCQAJ
> 
> The idea is to convert the (currently unused) "pad" bytes in the
> SPL header into an area where data can be passed to U-Boot. To
> do this safely, we have to make sure that we're actually using
> our "sunxi" flavor of the SPL, and not the Allwinner boot0.
> 
> The modified mksunxiboot introduces a special signature to the
> SPL header in place of the "pub_head_size" field. This can be
> used to reliably distinguish between compatible versions of sunxi
> SPL and anything else (older variants or Allwinner's boot0).
> 
> Signed-off-by: Bernhard Nortmann <bernhard.nortmann@web.de>
> ---
> 
> Changes in v2:
> - Rename field to fel_script_address, discard fel_data_size
> - Clearing header fields is no longer needed, as mksunxiboot.c zeroes entire image first
> 
>  tools/mksunxiboot.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/mksunxiboot.c b/tools/mksunxiboot.c
> index 676d392..cb0865c 100644
> --- a/tools/mksunxiboot.c
> +++ b/tools/mksunxiboot.c
> @@ -27,12 +27,29 @@ struct boot_file_head {
>  	 * by the boot ROM. To be compatible with Allwinner tools we
>  	 * would need to implement the proper fields here instead of
>  	 * padding.
> +	 *
> +	 * Actually we want the ability to recognize our "sunxi" variant
> +	 * of the SPL. To do so, let's place a special signature into the
> +	 * "pub_head_size" field. We can reasonably expect Allwinner's
> +	 * boot0 to always have the upper 16 bits of this set to 0 (after
> +	 * all the value shouldn't be larger than the limit imposed by
> +	 * SRAM size).
> +	 * If the signature is present (at 0x14), then we know it's safe
> +	 * to use the remaining 8 bytes (at 0x18) for our own purposes.
> +	 * (E.g. sunxi-tools "fel" utility can pass information there.)
>  	 */
> -	uint8_t pad[12];		/* align to 32 bytes */
> +	union {
> +		uint32_t pub_head_size;
> +		uint8_t spl_signature[4];
> +	};
> +	uint32_t fel_script_address;
> +	uint32_t reserved;		/* padding, align to 32 bytes */
>  };
>  
>  #define BOOT0_MAGIC                     "eGON.BT0"
>  #define STAMP_VALUE                     0x5F0A6C39
> +#define SPL_SIGNATURE			"SPL" /* marks "sunxi" header */
> +#define SPL_HEADER_VERSION		1
>  
>  /* check sum functon from sun4i boot code */
>  int gen_check_sum(struct boot_file_head *head_p)
> @@ -133,6 +150,10 @@ int main(int argc, char *argv[])
>  		ALIGN(file_size + sizeof(struct boot_file_head), BLOCK_SIZE);
>  	img.header.b_instruction = cpu_to_le32(img.header.b_instruction);
>  	img.header.length = cpu_to_le32(img.header.length);
> +
> +	memcpy(img.header.spl_signature, SPL_SIGNATURE, 3); /* "sunxi" marker */
> +	img.header.spl_signature[3] = SPL_HEADER_VERSION;
> +
>  	gen_check_sum(&img.header);
>  
>  	count = write(fd_out, &img, le32_to_cpu(img.header.length));

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

-- 
Best regards,
Siarhei Siamashka