linux-kernel - Re: [RFC PATCH 1/2] mtd: rawnand: handle ONFI revision number field being 0

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Date:   Mon, 18 Jun 2018 15:05:21 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Chris Packham <chris.packham@...iedtelesis.co.nz>
Cc:     boris.brezillon@...tlin.com, dwmw2@...radead.org,
        computersforpeace@...il.com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Richard Weinberger <richard@....at>,
        Marek Vasut <marek.vasut@...il.com>
Subject: Re: [RFC PATCH 1/2] mtd: rawnand: handle ONFI revision number field
 being 0

Hi Chris,

On Mon, 18 Jun 2018 16:52:54 +1200, Chris Packham
<chris.packham@...iedtelesis.co.nz> wrote:

> Some Micron NAND chips (MT29F1G08ABAFAWP-ITE:F) report 00 00 for the
> revision number field of the ONFI parameter page. Rather than rejecting
> these outright assume ONFI version 1.0 if the revision number is 00 00.
> 

Thanks for getting your hands into this.

> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
> ---
> At the moment I haven't qualified this check on anything, I should
> probably at least include vendor == MICRON.

The more I think about it the more I convince myself that this is not
needed. If the 4 first bytes are "ONFI", then the chip is ONFI...

Then what you do below is simple and readable and (sadly) probably
right.

> 
> As far as I can tell revision number == 0 is not permitted by the ONFI
> spec but this wouldn't be the first time a vendor has ignored a spec. On
> the other hand maybe I'm reading the spec wrong and someone here will
> say "oh 0 means ...".
> 
>  drivers/mtd/nand/raw/nand_base.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> index 0cd3e216b95c..1691c7005ae4 100644
> --- a/drivers/mtd/nand/raw/nand_base.c
> +++ b/drivers/mtd/nand/raw/nand_base.c
> @@ -5184,6 +5184,8 @@ static int nand_flash_detect_onfi(struct nand_chip *chip)
>  		chip->parameters.onfi.version = 20;
>  	else if (val & (1 << 1))
>  		chip->parameters.onfi.version = 10;
> +	else if (val == 0)
> +		chip->parameters.onfi.version = 10;
>  
>  	if (!chip->parameters.onfi.version) {
>  		pr_info("unsupported ONFI version: %d\n", val);

Regards,
Miquèl