[U-Boot] NAND bad block Query

[Scott Wood <scottwood@freescale.com>]

On Wed, 2014-02-12 at 21:04 +0000, Gray Remlin wrote:
> Example taken from include/configs/sheevaplug.h
> 
> #ifdef CONFIG_CMD_NAND
> #define CONFIG_ENV_IS_IN_NAND           1
> #define CONFIG_ENV_SECT_SIZE            0x20000 /* 128K */
> #else
> #define CONFIG_ENV_IS_NOWHERE           1       /* if env in SDRAM */
> #endif
> /*
>  * max 4k env size is enough, but in case of nand
>  * it has to be rounded to sector size
>  */
> #define CONFIG_ENV_SIZE                 0x20000 /* 128k */
> #define CONFIG_ENV_ADDR                 0x60000
> #define CONFIG_ENV_OFFSET               0x60000 /* env starts here */
> 
> In the above configuration CONFIG_ENV_SIZE == CONFIG_ENV_SECT_SIZE, that
> is, the erase block size.
> 
> If there is just one bad block in the NAND mapped for the environment
> does this mean that 'saveenv' will fail ?
> 
> If so, shouldn't CONFIG_ENV_SIZE be set to less than
> CONFIG_ENV_SECT_SIZE (but be a multiple of the write sector size) to
> allow for bad block skipping ?
> 
> I am tired and have a headache that wont go, please don't scold me too
> harshly if I am being stupid....

Reducing CONFIG_ENV_SIZE would speed up I/O and CRC calculation, but it
would not help with bad block skipping, because the granularity of
skipping is the 128k block, not the 4k page.

What you want is CONFIG_ENV_RANGE.

-Scott