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From:   Chuanhong Guo <gch981213@gmail.com>
Date:   Mon, 6 Apr 2020 13:18:22 +0800
Message-ID: <CAJsYDVLA3fgjBGdStkiZeqEv8q2j2sUdDzgj3QdahB=tvyYJWg@mail.gmail.com>
Subject: Re: [PATCH] Revert "mtd: spi-nor: Add 4B_OPCODES flag to w25q256"
To:     Robert Marko <robimarko@gmail.com>, linux-mtd@lists.infradead.org
Cc:     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 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.

-- 
Regards,
Chuanhong Guo