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From: Miquel Raynal <miquel.raynal@bootlin.com>
To: zdhays@gmail.com
Cc: Vignesh Raghavendra <vigneshr@ti.com>,
	Boris Brezillon <bbrezillon@kernel.org>,
	Richard Weinberger <richard@nod.at>,
	zhays@lexmark.com, Marco Felsch <m.felsch@pengutronix.de>,
	Frieder Schrempf <frieder.schrempf@kontron.de>,
	linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Piotr Sroka <piotrs@cadence.com>
Subject: Re: [PATCH v1] mtd: rawnand: micron: don't error out if internal ECC is set
Date: Thu, 16 Jan 2020 19:22:21 +0100
Message-ID: <20200116192221.49986c13@xps13> (raw)
In-Reply-To: <20200110162503.7185-1-zdhays@gmail.com>

Hi Zak,

zdhays@gmail.com wrote on Fri, 10 Jan 2020 11:25:01 -0500:

> From: Zak Hays <zdhays@gmail.com>
> 
> Recent changes to the driver require use of on-die correction if
> the internal ECC enable bit is set. On some Micron parts, this bit
> is enabled by default and there is no method for disabling it.
> 
> This is a false assumption though as that bit being enabled does not
> necessarily mean that the on-die ECC *has* to be used. It has been
> verified with a Micron FAE that other methods of error correction are
> still valid even if this bit is set.
> 
> HW ECC offers generally higher performance than on-die so it is
> preferred in some situations. This also allows multiple NAND parts to
> be supported on the same PCB as some parts may not support on-die
> error correction.
> 
> With that in mind, only throw a warning that the on-die bit is set
> and allow the init to continue.

I don't think I can take this patch as-is. We must find a reliable way
to discriminate Micron parts features. If we cannot (I think we can't
before of the endless list of bugs they have introduced without
documenting them), the best way is to build a static table.

> 
> Signed-off-by: Zak Hays <zdhays@gmail.com>
> ---
>  drivers/mtd/nand/raw/nand_micron.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/nand_micron.c b/drivers/mtd/nand/raw/nand_micron.c
> index 56654030ec7f..ec40c76443be 100644
> --- a/drivers/mtd/nand/raw/nand_micron.c
> +++ b/drivers/mtd/nand/raw/nand_micron.c
> @@ -455,9 +455,7 @@ static int micron_nand_init(struct nand_chip *chip)
>  
>  	if (ondie == MICRON_ON_DIE_MANDATORY &&
>  	    chip->ecc.mode != NAND_ECC_ON_DIE) {
> -		pr_err("On-die ECC forcefully enabled, not supported\n");
> -		ret = -EINVAL;
> -		goto err_free_manuf_data;
> +		pr_warn("WARNING: On-die ECC forcefully enabled, use caution with other methods\n");
>  	}
>  
>  	if (chip->ecc.mode == NAND_ECC_ON_DIE) {

Thanks,
Miquèl

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Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-10 16:25 zdhays
2020-01-16 18:22 ` Miquel Raynal [this message]
2020-01-17  7:10   ` Marco Felsch
     [not found]     ` <CANZat+hHJy0H17xGmOP003_M1yWesJ2BjoPmW3hr7CS=HuQR+g@mail.gmail.com>
2020-01-17 19:32       ` Zak Hays

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