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From:   Robert Marko <robimarko@gmail.com>
Date:   Mon, 6 Apr 2020 14:23:44 +0200
Message-ID: <CAOX2RU7ZU0Jj71YCAoP=qaqUomaHKTi=XMV8wGvwRg_fYpfoMg@mail.gmail.com>
Subject: Re: [PATCH] Revert "mtd: spi-nor: Add 4B_OPCODES flag to w25q256"
To:     Chuanhong Guo <gch981213@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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On Mon, 6 Apr 2020 at 07:18, Chuanhong Guo <gch981213@gmail.com> wrote:
>
> Hi Robert!
>
> On Sat, Apr 4, 2020 at 9:01 PM Chuanhong Guo <gch981213@gmail.com> wrote:
> > "line over 80 characters" warning produced by checkpatch.pl isn't
> > fixed because I think a revert commit should bring a file back to
> > what it was before.
> > I don't have a w25q256jv available and can't compare SFDP table
> > to create a fix similar to mx25l25635 one.
>
> I just tried and unable to dump SFDP on my W25Q256FV,
> probably because my chip is too old to have one.
> Could you check if your W25Q256JV has this and dump it?
> Just add some prints in spi_nor_read_sfdp.
> If a 4-byte address instruction table is present, current kernel
> should be able to discover 4B_OPCODES support automatically.
> Even if that's not the case we may still be able to distinguish
> W25Q256FV and W25Q256JV using SFDP table.

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.
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.

Best regards
Robert
>
> --
> Regards,
> Chuanhong Guo

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