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

[Hans de Goede]

Hi,

On 02-09-15 15:17, Bernhard Nortmann 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 at web.de>
> ---
>
>   tools/mksunxiboot.c | 27 ++++++++++++++++++++++++++-
>   1 file changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/tools/mksunxiboot.c b/tools/mksunxiboot.c
> index 3361251..58bc5c7 100644
> --- a/tools/mksunxiboot.c
> +++ b/tools/mksunxiboot.c
> @@ -27,12 +27,31 @@ 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.)
> +	 *
> +	 * The overall header size still sums up to 32 bytes.
>   	 */
> -	uint8_t pad[12];		/* align to 32 bytes */
> +	union {
> +		uint32_t pub_head_size;
> +		uint8_t spl_signature[4];
> +	};
> +	uint32_t fel_data_address;
> +	uint32_t fel_data_size;

I believe these 2 should be renamed to:

	uint32_t fel_boot_script_address;
	uint32_t fel_boot_script_size;

To properly reflect what they are (they are not some abstract
data, they are specifically a boot.scr image)

With that changed and Siarhei's ack for the series (I'm assuming
Sairhei will take care of the sunxi-tools side of things),
I'm ok with merging this.

Regards,

Hans



I
>   };
>
>   #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 +152,12 @@ 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;
> +	img.header.fel_data_address = 0; /* ensure fields are zeroed */
> +	img.header.fel_data_size = 0;
> +
>   	gen_check_sum(&img.header);
>
>   	count = write(fd_out, &img, le32_to_cpu(img.header.length));
>