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From:   <Tudor.Ambarus@microchip.com>
To:     <danielwa@cisco.com>
CC:     <xe-linux-external@cisco.com>, <miquel.raynal@bootlin.com>,
        <richard@nod.at>, <vigneshr@ti.com>,
        <linux-mtd@lists.infradead.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mtd: spi-nor: Add 4B_OPCODES flag to n25q256a
Thread-Topic: [PATCH] mtd: spi-nor: Add 4B_OPCODES flag to n25q256a
Thread-Index: AQHWFyrJEeAl1Y63FkSdbq93yQPoxg==
Date:   Tue, 21 Apr 2020 04:52:01 +0000
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On Monday, April 20, 2020 7:25:51 PM EEST Daniel Walker (danielwa) wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know th=
e
> content is safe
> On Mon, Apr 20, 2020 at 03:45:59PM +0000, Tudor.Ambarus@microchip.com wro=
te:
> > Hi, Daniel,
> >=20
> > On Friday, April 17, 2020 8:46:19 PM EEST Daniel Walker wrote:
> > > EXTERNAL EMAIL: Do not click links or open attachments unless you kno=
w
> > > the
> > > content is safe
> > >=20
> > > The n25q256a supports 4-byte opcodes so lets add the flag.
> >=20
> > This is not true for all the n25q256a flashes. SPINOR_OP_PP_4B,
> > SPINOR_OP_BE_4K_4B and SPINOR_OP_SE_4B are valid just for the part numb=
ers
> > N25Q256A83ESF40x, N25Q256A83E1240x, and N25Q256A83ESFA0F.
> >=20
> > You need to differentiate between the aforementioned flashes and the re=
st
> > in the n25q256a, in order to add the 4-byte opcodes flag.
>=20
> How do you suggest I do that ? Can I add a new entry into this table with
> more specific information about the chips ?
>=20

We need to find a differentiator at runtime. If we are lucky, there might b=
e=20
some SFDP changes between the 4-byte opcodes capable flashes and the rest.=
=20
Please dump all the sfdp tables, we can start from there. There's a thread=
=20
that might interest you, see http://u-boot.10912.n7.nabble.com/Regressions-=
in-MTD-SPI-FLASH-td382956.html#a383126.

A more elegant way to solve it, is by parsing the 4bait sfdp table, but I=20
haven't checked if this flash supports it or not. Anyway, not something tha=
t=20
we can control, the manufacturer should add it.

Cheers,
ta