linux-kernel - Re: [PATCH 1/3] mtd: nand: add support for "nand-ecc-algo" DT property

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Date:	Mon, 25 Apr 2016 12:11:53 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Rafał Miłecki <zajec5@...il.com>,
	Rob Herring <robh+dt@...nel.org>
Cc:	linux-mtd@...ts.infradead.org, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Richard Weinberger <richard@....at>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	devicetree@...r.kernel.org (open list:OPEN FIRMWARE AND FLATTENED
	DEVICE TREE BINDINGS), linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH 1/3] mtd: nand: add support for "nand-ecc-algo" DT
 property

On Fri, 22 Apr 2016 13:23:13 +0200
Rafał Miłecki <zajec5@...il.com> wrote:

> So far it was only possible to specify ECC algorithm using "soft" and
> "soft_bch" values of nand-ecc-mode prop. There wasn't a way to specify
> it for a hardware ECC mode.
> 
> Now that we have independent field in NAND subsystem for storing info
> about ECC algorithm we may also add support for this new DT property.
> 
> Signed-off-by: Rafał Miłecki <zajec5@...il.com>
> ---
>  Documentation/devicetree/bindings/mtd/nand.txt |  2 ++
>  drivers/mtd/nand/nand_base.c                   | 20 +++++++++++++-------
>  2 files changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/mtd/nand.txt b/Documentation/devicetree/bindings/mtd/nand.txt
> index a17662b..5ac4ab7 100644
> --- a/Documentation/devicetree/bindings/mtd/nand.txt
> +++ b/Documentation/devicetree/bindings/mtd/nand.txt
> @@ -22,6 +22,8 @@ Optional NAND chip properties:
>  - nand-ecc-mode : String, operation mode of the NAND ecc mode.
>    Supported values are: "none", "soft", "hw", "hw_syndrome", "hw_oob_first",
>    "soft_bch".
> +- nand-ecc-algo: string, algorithm of NAND ECC.
> +		 Supported values are: "hamming", "bch".

Rob, any objection to this binding change (and the one in patch 3).
Please note that everything is backward compatible.

Thanks,

Boris

>  - nand-bus-width : 8 or 16 bus width if not present 8
>  - nand-on-flash-bbt: boolean to enable on flash bbt option if not present false
>  
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index 7bc37b4..a5417a0 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -4003,17 +4003,23 @@ static int of_get_nand_ecc_mode(struct device_node *np)
>  	return -ENODEV;
>  }
>  
> +static const char * const nand_ecc_algos[] = {
> +	[NAND_ECC_HAMMING]	= "hamming",
> +	[NAND_ECC_BCH]		= "bch",
> +};
> +
>  static int of_get_nand_ecc_algo(struct device_node *np)
>  {
>  	const char *pm;
> -	int err;
> +	int err, i;
>  
> -	/*
> -	 * TODO: Read ECC algo OF property and map it to enum nand_ecc_algo.
> -	 * It's not implemented yet as currently NAND subsystem ignores
> -	 * algorithm explicitly set this way. Once it's handled we should
> -	 * document & support new property.
> -	 */
> +	err = of_property_read_string(np, "nand-ecc-algo", &pm);
> +	if (!err) {
> +		for (i = 0; i < ARRAY_SIZE(nand_ecc_algos); i++)
> +			if (!strcasecmp(pm, nand_ecc_algos[i]))
> +				return i;
> +		return -ENODEV;
> +	}
>  
>  	/*
>  	 * For backward compatibility we also read "nand-ecc-mode" checking



-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com