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From:   Chuanhong Guo <gch981213@gmail.com>
Date:   Mon, 6 Apr 2020 20:49:02 +0800
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Subject: Re: [PATCH] Revert "mtd: spi-nor: Add 4B_OPCODES flag to w25q256"
To:     Robert Marko <robimarko@gmail.com>
Cc:     linux-mtd@lists.infradead.org,
        Tudor Ambarus <tudor.ambarus@microchip.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        open list <linux-kernel@vger.kernel.org>
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Hi!

On Mon, Apr 6, 2020 at 8:23 PM Robert Marko <robimarko@gmail.com> wrote:
>
> It appears that W25Q256JV has an SFDP table and in it advertises 3B or 4B modes.
> >
> > [    1.957903] spi_qup 78b5000.spi: IN:block:16, fifo:64, OUT:block:16, fifo:64
> > [    1.962185] SFDP advertises 3B or 4B
> > [    1.977393] spi-nor spi0.0: w25q256 (32768 Kbytes)
> >
> I have used the attached patch to check what does the SFDP DWORD 1 advertises.
> If FV version has or does not advertise 4B support than that can be
> used to differentiate them.

My old w25q256fv spits all 0xFF to 0x5a read sfdp instruction.
I've asked someone with a newer w25q256fv to dump the entire SFDP
for me and it's in the attachment. You could do a comparison between
w25q256jv with this dump.

> Can you apply this patch and check what the FV version advertises as I
> don't have a device using that revision.
> FV version also should have SFDP as datasheet for it clearly advertises is.

I've checked the sfdp dump in the attachment and it's also advertising
3B or 4B in 1st BFPT dword.

-- 
Regards,
Chuanhong Guo

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