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Date:   Fri, 13 May 2022 19:21:52 +0200
From:   Michael Walle <michael@walle.cc>
To:     Alexander Sverdlin <alexander.sverdlin@nokia.com>
Cc:     linux-mtd@lists.infradead.org,
        Tudor Ambarus <tudor.ambarus@microchip.com>,
        Pratyush Yadav <p.yadav@ti.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mtd: spi-nor: Support Dual and Quad Read on Macronix
 mx25u25635f
In-Reply-To: <d59ec4e0-3bce-2b44-1fc5-54a26fe77c7f@nokia.com>
References: <20220513094759.44185-1-alexander.sverdlin@nokia.com>
 <34eccc66cc75dd0ffbf8a77780b6f8a7@walle.cc>
 <d59ec4e0-3bce-2b44-1fc5-54a26fe77c7f@nokia.com>
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Hi,

Am 2022-05-13 18:09, schrieb Alexander Sverdlin:
>>> According to datasheet both Dual and Quad Read is supported. The read 
>>> test
>>> shows x3.8 speed gain.
>> 
>> Does it have SFDP? Try adding PARSE_SFDP instead of the
>> NO_SFDP_FLAGS.
> 
> Some issues with its SFDP were known:
> https://patchwork.ozlabs.org/project/linux-mtd/patch/1492068234-9509-1-git-send-email-dev@kresin.me/

That doesn't seem to be the case for your flash. The quad and
dual flags you've added, will enable SFDP parsing anyway. So
instead of adding these flags, just adding PARSE_SFDP should
work, too. We still have to keep the SPI_NOR_4B_OPCODES.

>> Please post an SFDP dump of this flash [1].

Thanks.

>> xxd -p /sys/bus/spi/devices/spi0.0/sfdp
> 53464450060102ff00060110300000ffc2000104100100ff84000102c000
> 00ffffffffffffffffffffffffffffffffffe520fbffffffff0f44eb086b
> 083b04bbfeffffffffff00ffffff44eb0c200f5210d800ff8749b50082d2
> 04d24403673830b030b0f7bdd55c4a9e29fff050f985ffffffffffffffff
> ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
> ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
> ffffffffffffffffffffffff7f8fffff215cdcffffffffffffffffffffff
                           ^^^^^^^^^^^^^^^^

That's the 4BAIT table.


> ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
> ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
> ffff002050169df9c06485cbffffffffffff

-michael