Re: [PATCH v3 1/2] mtd: brcmnand: Force 8bit mode before doing nand_scan_ident()

[Brian Norris]

On Fri, Oct 23, 2015 at 10:46:12AM +0530, Anup Patel wrote:
> Just like other NAND controllers, the NAND READID command only works
> in 8bit mode for all versions of BRCMNAND controller.
> 
> This patch forces 8bit mode for each NAND CS in brcmnand_init_cs()
> before doing nand_scan_ident() to ensure that BRCMNAND controller
> is in 8bit mode when NAND READID command is issued.
> 
> Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxxxx>
> Reviewed-by: Ray Jui <rjui@xxxxxxxxxxxx>
> Reviewed-by: Scott Branden <sbranden@xxxxxxxxxxxx>
> ---
>  drivers/mtd/nand/brcmnand/brcmnand.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
> index 4cba03d..0be8ef9 100644
> --- a/drivers/mtd/nand/brcmnand/brcmnand.c
> +++ b/drivers/mtd/nand/brcmnand/brcmnand.c
> @@ -1888,6 +1888,7 @@ static int brcmnand_init_cs(struct brcmnand_host *host)
>  	struct mtd_info *mtd;
>  	struct nand_chip *chip;
>  	int ret;
> +	u16 cfg_offs;
>  	struct mtd_part_parser_data ppdata = { .of_node = dn };
>  
>  	ret = of_property_read_u32(dn, "reg", &host->cs);
> @@ -1930,6 +1931,14 @@ static int brcmnand_init_cs(struct brcmnand_host *host)
>  
>  	chip->controller = &ctrl->controller;
>  
> +	/*
> +	 * The bootloader might have configured 16bit mode but
> +	 * NAND READID command only works in 8bit mode. We force
> +	 * 8bit mode here to ensure that NAND READID commands works.
> +	 */
> +	cfg_offs = brcmnand_cs_offset(ctrl, host->cs, BRCMNAND_CS_CFG);
> +	nand_writereg(ctrl, cfg_offs, nand_readreg(ctrl, cfg_offs) & ~BIT(23));

Can we get a new enum for cfg bits? Unfortunately, I never managed that
in brcmnand_set_cfg(); just magic numbers :( But I'd like to stop that
if we're going to have to touch these bits outside of
brcmnand_set_cfg().

> +
>  	if (nand_scan_ident(mtd, 1, NULL))
>  		return -ENXIO;
>  

How about the following, as a preparatory patch? Only compile tested.