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From:   <Tudor.Ambarus@microchip.com>
To:     <mantas@8devices.com>, <gch981213@gmail.com>, <robimarko@gmail.com>
CC:     <linux-mtd@lists.infradead.org>, <miquel.raynal@bootlin.com>,
        <richard@nod.at>, <vigneshr@ti.com>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mtd: spi-nor: fix 4-byte opcode support for w25q256
Thread-Topic: [PATCH] mtd: spi-nor: fix 4-byte opcode support for w25q256
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Date:   Mon, 20 Apr 2020 10:53:11 +0000
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On Wednesday, April 15, 2020 4:48:30 PM EEST Mantas Pucka wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know th=
e
> content is safe
>=20
> There are 2 different chips (w25q256fv and w25q256jv) that share
> the same JEDEC ID. Only w25q256jv fully supports 4-byte opcodes.
> Use SFDP header version to differentiate between them.
>=20
> Signed-off-by: Mantas Pucka <mantas@8devices.com>
> ---
>  drivers/mtd/spi-nor/sfdp.c    |  4 ----
>  drivers/mtd/spi-nor/sfdp.h    |  6 ++++++
>  drivers/mtd/spi-nor/winbond.c | 30 ++++++++++++++++++++++++++++--
>  3 files changed, 34 insertions(+), 6 deletions(-)
>=20
> diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
> index f6038d3..27838f6 100644
> --- a/drivers/mtd/spi-nor/sfdp.c
> +++ b/drivers/mtd/spi-nor/sfdp.c
> @@ -21,10 +21,6 @@
>  #define SFDP_4BAIT_ID          0xff84  /* 4-byte Address Instruction Tab=
le
> */
>=20
>  #define SFDP_SIGNATURE         0x50444653U
> -#define SFDP_JESD216_MAJOR     1
> -#define SFDP_JESD216_MINOR     0
> -#define SFDP_JESD216A_MINOR    5
> -#define SFDP_JESD216B_MINOR    6
>=20
>  struct sfdp_header {
>         u32             signature; /* Ox50444653U <=3D> "SFDP" */
> diff --git a/drivers/mtd/spi-nor/sfdp.h b/drivers/mtd/spi-nor/sfdp.h
> index e0a8ded..b84abd0 100644
> --- a/drivers/mtd/spi-nor/sfdp.h
> +++ b/drivers/mtd/spi-nor/sfdp.h
> @@ -7,6 +7,12 @@
>  #ifndef __LINUX_MTD_SFDP_H
>  #define __LINUX_MTD_SFDP_H
>=20
> +/* SFDP revisions */
> +#define SFDP_JESD216_MAJOR     1
> +#define SFDP_JESD216_MINOR     0
> +#define SFDP_JESD216A_MINOR    5
> +#define SFDP_JESD216B_MINOR    6
> +
>  /* Basic Flash Parameter Table */
>=20
>  /*
> diff --git a/drivers/mtd/spi-nor/winbond.c b/drivers/mtd/spi-nor/winbond.=
c
> index 17deaba..50b2478 100644
> --- a/drivers/mtd/spi-nor/winbond.c
> +++ b/drivers/mtd/spi-nor/winbond.c
> @@ -8,6 +8,32 @@
>=20
>  #include "core.h"
>=20
> +static int
> +w25q256_post_bfpt_fixups(struct spi_nor *nor,
> +                        const struct sfdp_parameter_header *bfpt_header,
> +                        const struct sfdp_bfpt *bfpt,
> +                        struct spi_nor_flash_parameter *params)
> +{
> +       /*
> +        * W25Q256JV supports 4B opcodes but W25Q256FV does not.
> +        * Unfortunately, Winbond has re-used the same JEDEC ID for both
> +        * variants which prevents us from defining a new entry in the pa=
rts
> +        * table.
> +        * To differentiate between W25Q256JV and W25Q256FV check SFDP
> header +        * version: only JV has JESD216A compliant structure
> (version 5) +        */
> +
> +       if (bfpt_header->major =3D=3D SFDP_JESD216_MAJOR &&
> +           bfpt_header->minor =3D=3D SFDP_JESD216A_MINOR)

Not sure if this is generic enough. Are you sure that the JV version will=20
never have an update for the sfdp tables?

> +               nor->flags |=3D SNOR_F_4B_OPCODES;
> +
> +       return 0;
> +}
> +
> +static struct spi_nor_fixups w25q256_fixups =3D {
> +       .post_bfpt =3D w25q256_post_bfpt_fixups,
> +};
> +

If the post_bfpt hook is called, you already have a valid bfpt table. If th=
e=20
differentiator between the JV and FV versions is that only the JV defines t=
he=20
SFDP tables, then your w25q256_post_bfpt_fixups() can look as:

static int w25q256_post_bfpt_fixups()
{
	nor->flags |=3D SNOR_F_4B_OPCODES;
	return 0;
}

Cheers,
ta