linux-kernel - Re: [PATCH v9 13/19] mtd: spi-nor: sfdp: do not make invalid quad enable fatal

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Message-ID: <2267830.vuSd8QnXzO@192.168.0.120>
Date:   Sat, 30 May 2020 18:42:25 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <p.yadav@...com>
CC:     <miquel.raynal@...tlin.com>, <richard@....at>, <vigneshr@...com>,
        <broonie@...nel.org>, <Nicolas.Ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <Ludovic.Desroches@...rochip.com>,
        <matthias.bgg@...il.com>, <michal.simek@...inx.com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-spi@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, <nsekhar@...com>,
        <boris.brezillon@...labora.com>, <masonccyang@...c.com.tw>
Subject: Re: [PATCH v9 13/19] mtd: spi-nor: sfdp: do not make invalid quad
 enable fatal

On Monday, May 25, 2020 12:15:38 PM EEST Pratyush Yadav wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the
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> 
> The Micron MT35XU512ABA flash does not support the quad enable bit. But
> instead of programming the Quad Enable Require field to 000b ("Device
> does not have a QE bit"), it is programmed to 111b ("Reserved").
> 
> While this is technically incorrect, it is not reason enough to abort
> BFPT parsing. Instead, continue BFPT parsing assuming there is no quad
> enable bit present.
> 
> Signed-off-by: Pratyush Yadav <p.yadav@...com>
> ---
>  drivers/mtd/spi-nor/sfdp.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
> index 052cabb52df9..9fd3d8d9a127 100644
> --- a/drivers/mtd/spi-nor/sfdp.c
> +++ b/drivers/mtd/spi-nor/sfdp.c
> @@ -576,10 +576,6 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
> 
>         /* Quad Enable Requirements. */
>         switch (bfpt.dwords[BFPT_DWORD(15)] & BFPT_DWORD15_QER_MASK) {
> -       case BFPT_DWORD15_QER_NONE:
> -               params->quad_enable = NULL;
> -               break;
> -
>         case BFPT_DWORD15_QER_SR2_BIT1_BUGGY:
>                 /*
>                  * Writing only one byte to the Status Register has the
> @@ -616,8 +612,10 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
>                 params->quad_enable = spi_nor_sr2_bit1_quad_enable;
>                 break;
> 
> +       case BFPT_DWORD15_QER_NONE:
>         default:
> -               return -EINVAL;
> +               params->quad_enable = NULL;
> +               break;

I would just add a dev_dbg message and break the switch.
	dev_dbg(nor->dev, "BFPT QER reserved value used.\n");
	break;

You will then have to set params->quad_enable = NULL; in a post_bfpt hook.

Cheers,
ta