linux-kernel - Re: [PATCH 9/9] mtd: rawnand: xway: Keep the driver compatible with on-die ECC engines

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Date:   Mon, 4 Oct 2021 17:40:48 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tudor Ambarus <Tudor.Ambarus@...rochip.com>
Cc:     <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org, Jan Hoffmann <jan@....eu>,
        Kestrel seventyfour <kestrelseventyfour@...il.com>
Subject: Re: [PATCH 9/9] mtd: rawnand: xway: Keep the driver compatible with
 on-die ECC engines

Hi Jan,

miquel.raynal@...tlin.com wrote on Wed, 29 Sep 2021 00:22:48 +0200:

> Following the introduction of the generic ECC engine infrastructure, it
> was necessary to reorganize the code and move the ECC configuration in
> the ->attach_chip() hook. Failing to do that properly lead to a first
> series of fixes supposed to stabilize the situation. Unfortunately, this
> only fixed the use of software ECC engines, preventing any other kind of
> engine to be used, including on-die ones.
> 
> It is now time to (finally) fix the situation by ensuring that we still
> provide a default (eg. software ECC) but will still support different
> ECC engines such as on-die ECC engines if properly described in the
> device tree.
> 
> There are no changes needed on the core side in order to do this, but we
> just need to leverage the logic there which allows:
> 1- a subsystem default (set to Host engines in the raw NAND world)
> 2- a driver specific default (here set to software ECC engines)
> 3- any type of engine requested by the user (ie. described in the DT)
> 
> As the raw NAND subsystem has not yet been fully converted to the ECC
> engine infrastructure, in order to provide a default ECC engine for this
> driver we need to set chip->ecc.engine_type *before* calling
> nand_scan(). During the initialization step, the core will consider this
> entry as the default engine for this driver. This value may of course
> be overloaded by the user if the usual DT properties are provided.
> 
> Fixes: d525914b5bd8 ("mtd: rawnand: xway: Move the ECC initialization to ->attach_chip()")
> Cc: stable@...r.kernel.org
> Cc: Jan Hoffmann <jan@....eu>

I think you already tested this change and validated it, would you mind
providing your Tested-by?

> Cc: Kestrel seventyfour <kestrelseventyfour@...il.com>
> Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> ---
>  drivers/mtd/nand/raw/xway_nand.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/xway_nand.c b/drivers/mtd/nand/raw/xway_nand.c
> index 26751976e502..236fd8c5a958 100644
> --- a/drivers/mtd/nand/raw/xway_nand.c
> +++ b/drivers/mtd/nand/raw/xway_nand.c
> @@ -148,9 +148,8 @@ static void xway_write_buf(struct nand_chip *chip, const u_char *buf, int len)
>  
>  static int xway_attach_chip(struct nand_chip *chip)
>  {
> -	chip->ecc.engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
> -
> -	if (chip->ecc.algo == NAND_ECC_ALGO_UNKNOWN)
> +	if (chip->ecc.engine_type == NAND_ECC_ENGINE_TYPE_SOFT &&
> +	    chip->ecc.algo == NAND_ECC_ALGO_UNKNOWN)
>  		chip->ecc.algo = NAND_ECC_ALGO_HAMMING;
>  
>  	return 0;
> @@ -219,6 +218,13 @@ static int xway_nand_probe(struct platform_device *pdev)
>  		    | NAND_CON_SE_P | NAND_CON_WP_P | NAND_CON_PRE_P
>  		    | cs_flag, EBU_NAND_CON);
>  
> +	/*
> +	 * This driver assumes that the default ECC engine should be TYPE_SOFT.
> +	 * Set ->engine_type before registering the NAND devices in order to
> +	 * provide a driver specific default value.
> +	 */
> +	data->chip.ecc.engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
> +
>  	/* Scan to find existence of the device */
>  	err = nand_scan(&data->chip, 1);
>  	if (err)


Thanks,
Miquèl