linux-kernel - Re: [PATCH v4 05/16] mtd: spi-nor: default to address width of 3 for configurable widths

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Message-ID: <6b6384ad-d37a-eea6-af29-322e83924912@hisilicon.com>
Date:   Sun, 26 Apr 2020 11:53:53 +0800
From:   Yicong Yang <yangyicong@...ilicon.com>
To:     Pratyush Yadav <p.yadav@...com>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Mark Brown <broonie@...nel.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-spi@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
CC:     Sekhar Nori <nsekhar@...com>
Subject: Re: [PATCH v4 05/16] mtd: spi-nor: default to address width of 3 for
 configurable widths

On 2020/4/25 2:43, Pratyush Yadav wrote:
> JESD216D.01 says that when the address width can be 3 or 4, it defaults
> to 3 and enters 4-byte mode when given the appropriate command. So, when
> we see a configurable width, default to 3 and let flash that default to
> 4 change it in a post-bfpt fixup.
>
> This fixes SMPT parsing for flashes with configurable address width. If
> the SMPT descriptor advertises variable address width, we use
> nor->addr_width as the address width. But since it was not set to any
> value from the SFDP table, the read command uses an address width of 0,
> resulting in an incorrect read being issued.
>
> Signed-off-by: Pratyush Yadav <p.yadav@...com>
> ---
>  drivers/mtd/spi-nor/sfdp.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
> index f917631c8110..5cecc4ba2141 100644
> --- a/drivers/mtd/spi-nor/sfdp.c
> +++ b/drivers/mtd/spi-nor/sfdp.c
> @@ -460,6 +460,7 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
>  	/* Number of address bytes. */
>  	switch (bfpt.dwords[BFPT_DWORD(1)] & BFPT_DWORD1_ADDRESS_BYTES_MASK) {
>  	case BFPT_DWORD1_ADDRESS_BYTES_3_ONLY:
> +	case BFPT_DWORD1_ADDRESS_BYTES_3_OR_4:
>  		nor->addr_width = 3;
>  		break;

Should we also assign address width to 3 in default condition. At least we should not
leave it uninitialized here.

Regards,
Yicong


>