Re: [PATCH][v2] mtd: rawnand: fsl_ifc: Fix nand waitfunc return value

[Boris Brezillon <boris.brezillon@bootlin.com>]

On Tue, 20 Mar 2018 22:13:38 +0530
Jagdish Gediya <jagdish.gediya@nxp.com> wrote:

> As per the IFC hardware manual, Most significant 2 bytes in
> nand_fsr register are the outcome of NAND READ STATUS command.
> 
> So status value need to be shifted and aligned as per the nand
> framework requirement.
> 
> Fixes: 82771882d960 ("NAND Machine support for Integrated Flash Controller")
> Cc: stable@vger.kernel.org # v3.18+
> Signed-off-by: Jagdish Gediya <jagdish.gediya@nxp.com>
> Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
> ---
> Changes for v2: Incorporated comments from Boris Brezillon
>         - Added fixes tag
> 
>  drivers/mtd/nand/fsl_ifc_nand.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/nand/fsl_ifc_nand.c b/drivers/mtd/nand/fsl_ifc_nand.c
> index 9390cbd..0aa03ba 100644
> --- a/drivers/mtd/nand/fsl_ifc_nand.c
> +++ b/drivers/mtd/nand/fsl_ifc_nand.c
> @@ -643,12 +643,13 @@ static int fsl_ifc_wait(struct mtd_info *mtd, struct nand_chip *chip)
>  	fsl_ifc_run_command(mtd);
>  
>  	nand_fsr = ifc_in32(&ifc->ifc_nand.nand_fsr);
> -
> +	nand_fsr >>= 16;
> +	nand_fsr = (nand_fsr >> 8) | (nand_fsr << 8);

Why are you swapping the upper and lower bytes? If the NAND status is
stored in the upper byte of the fsr reg (bits 24 to 31), then shift the
value by 24 directly. Note that (nand_fsr << 8) is useless here since
you're masking nand_fsr with 0xff before returning it.

>  	/*
>  	 * The chip always seems to report that it is
>  	 * write-protected, even when it is not.
>  	 */
> -	return nand_fsr | NAND_STATUS_WP;
> +	return (nand_fsr & 0xff) | NAND_STATUS_WP;
>  }
>  
>  /*



-- 
Boris Brezillon, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com