[PATCH v2] mtd: nand: fix off-by-one read retry mode counting

[Huang Shijie]

On Wed, Feb 12, 2014 at 05:22:11PM -0800, Brian Norris wrote:
> A flash may support N read retry voltage threshold modes, numbered 1
> through N-1 (where mode 0 represents the initial state). However,
> nand_do_read_ops() tries to use mode 0 through N.
> 
> This off-by-one error shows up, for instance, when using nanddump, and
> we have cycled through available modes:
> 
>     nand: setting READ RETRY mode 0
>     nand: setting READ RETRY mode 1
>     nand: setting READ RETRY mode 2
>     nand: setting READ RETRY mode 3
>     nand: setting READ RETRY mode 4
>     nand: setting READ RETRY mode 5
>     nand: setting READ RETRY mode 6
>     nand: setting READ RETRY mode 7
>     nand: setting READ RETRY mode 8
>     libmtd: error!: cannot read 8192 bytes from mtd0 (eraseblock 20, offset 0)
>             error 22 (Invalid argument)
>     nanddump: error!: mtd_read
> 
> Tested on Micron MT29F64G08CBCBBH1, with 8 retry modes.
> 
> Signed-off-by: Brian Norris <computersforpeace at gmail.com>
> ---
> v1 -> v2: N modes means we should use modes 0 to N-1, not 0 to N
> 
>  drivers/mtd/nand/nand_base.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index 9be7842f300e..3cb1cefcd926 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -1586,7 +1586,7 @@ read_retry:
>  			}
>  
>  			if (mtd->ecc_stats.failed - ecc_failures) {
> -				if (retry_mode + 1 <= chip->read_retries) {
> +				if (retry_mode + 1 < chip->read_retries) {
>  					retry_mode++;
>  					ret = nand_setup_read_retry(mtd,
>  							retry_mode);
> -- 
> 1.8.3.2
> 
> 
> 

Acked-by: Huang Shijie <b32955 at freescale.com>