[U-Boot] [PATCH v2] sunxi_nand_spl: Be smarter about where to look for backup u-boot.bin

[Ian Campbell <ijc+uboot@hellion.org.uk>]

On Sun, 2015-09-20 at 15:39 -0400, Hans de Goede wrote:
> We know when u-boot is written to its own partition, in this case the
> layout always is:
> 
> eb 0 spl
> eb 1 spl-backup
> eb 2 u-boot
> eb 3 u-boot-backup
> 
> eb: erase-block
> 
> So if we cannot load u-boot from its primary offset we know exactly where
> to look for it.

Is it worth noting here (or perhaps in a code comment?) that the code
currently assumes that the first four ebs are of uniform size?

> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> Changes in v2:
> -Add an eraseblock_size helper variable to make the calculation for
> finding
>  the backup u-boot easier to understand
> ---
>  drivers/mtd/nand/sunxi_nand_spl.c | 26 ++++++++++++++++++++------
>  1 file changed, 20 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mtd/nand/sunxi_nand_spl.c
> b/drivers/mtd/nand/sunxi_nand_spl.c
> index 5985534..b0e07aa 100644
> --- a/drivers/mtd/nand/sunxi_nand_spl.c
> +++ b/drivers/mtd/nand/sunxi_nand_spl.c
> @@ -356,18 +356,32 @@ static int nand_read_buffer(uint32_t offs, unsigned
> int size, void *dest,
>  
>  int nand_spl_load_image(uint32_t offs, unsigned int size, void *dest)
>  {
> +#if CONFIG_SYS_NAND_U_BOOT_OFFS == CONFIG_SPL_PAD_TO
> +	/*
> +	 * u-boot-dtb.bin appended to SPL, use syndrome (like the BROM
> does)
> +	 * and try different erase block sizes to find the backup.
> +	 */
>  	const uint32_t boot_offsets[] = {
>  		0 * 1024 * 1024 + CONFIG_SYS_NAND_U_BOOT_OFFS,
>  		1 * 1024 * 1024 + CONFIG_SYS_NAND_U_BOOT_OFFS,
>  		2 * 1024 * 1024 + CONFIG_SYS_NAND_U_BOOT_OFFS,
>  		4 * 1024 * 1024 + CONFIG_SYS_NAND_U_BOOT_OFFS,
>  	};
> -	int i, syndrome;
> -
> -	if (CONFIG_SYS_NAND_U_BOOT_OFFS == CONFIG_SPL_PAD_TO)
> -		syndrome = 1; /* u-boot-dtb.bin appended to SPL */
> -	else
> -		syndrome = 0; /* u-boot-dtb.bin on its own partition */
> +	const int syndrome = 1;
> +#else
> +	/*
> +	 * u-boot-dtb.bin on its own partition, do not use syndrome, u
> -boot
> +	 * partition sits after 2 eraseblocks (spl, spl-backup), look
> for
> +	 * backup u-boot 1 erase block further.
> +	 */
> +	const uint32_t eraseblock_size = CONFIG_SYS_NAND_U_BOOT_OFFS /
> 2;
> +	const uint32_t boot_offsets[] = {
> +		CONFIG_SYS_NAND_U_BOOT_OFFS,
> +		CONFIG_SYS_NAND_U_BOOT_OFFS + eraseblock_size,
> +	};
> +	const int syndrome = 0;
> +#endif
> +	int i;
>  
>  	if (offs == CONFIG_SYS_NAND_U_BOOT_OFFS) {
>  		for (i = 0; i < ARRAY_SIZE(boot_offsets); i++) {