linux-kernel - Re: [PATCH v2 3/4] dt-bindings: mtd: macronix,mx25l12833f: add SPI-NOR chip

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Message-ID: <CANeKEMPAng8K1Gbab-MXP0KodS=r1Bzstsvg4zadWdu1O7wqWg@mail.gmail.com>
Date: Mon, 1 Jul 2024 13:03:01 +0200
From: Erez <erezgeva2@...il.com>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: Esben Haabendal <esben@...nix.com>, Erez Geva <erezgeva@...ime.org>, linux-mtd@...ts.infradead.org, 
	Pratyush Yadav <pratyush@...nel.org>, Michael Walle <mwalle@...nel.org>, linux-kernel@...r.kernel.org, 
	Miquel Raynal <miquel.raynal@...tlin.com>, Richard Weinberger <richard@....at>, 
	Vignesh Raghavendra <vigneshr@...com>, devicetree@...r.kernel.org, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Subject: Re: [PATCH v2 3/4] dt-bindings: mtd: macronix,mx25l12833f: add
 SPI-NOR chip

On Mon, 1 Jul 2024 at 12:23, Tudor Ambarus <tudor.ambarus@...aro.org> wrote:
>
>
>
> On 7/1/24 11:15 AM, Tudor Ambarus wrote:
> >
> >
> > On 7/1/24 10:46 AM, Erez wrote:
> >> When using mx25l12805d, we do not read SFDP.
> >> As it uses the no-SFDP flags.
> >> When using mx25l12833f hardware with mx25l12805d driver, it did not
> >> try to read the SFDP.
> >> Yet mx25l12833f does have SFDP, when I remove the no-SFDP flags, the
> >> driver fetch the SFDP.
> >>
> >> Secondly SFDP does not contain OTP information.
> >>
> >> mx25l12805d has two OTP regions of 128 KiB and 384 KiB (yes asymmetric).
> >> While mx25l12833f has two OTP regions of 512 KiB.
> >>
> >> How do we handle it?
> >
> > You would first try to parse SFDP and initialize the flash based on
> > SFDP. If there's no SFDP then you fallback to the flags declared at
> > flash declaration. Esben had a try recently, see [1]. I don't know if
> > there's any progress in that direction.
> >
>
> And you can then decide which OTP org to use based on whether SFDP is
> present or not.

That can work, but sound like a hack.
Is that really that important to hack?
Just for OTP, that very few use?
And if in the future Macronix adds a newer one with the same JEDEC ID,
but a different OTP size?
Macronix does not consult with the Linux Kernel on these matters.

Anyhow as I do not have the hardware anymore, I can not do more
changes and test them.

Erez


>
> > Also, you haven't mentioned anything about the testing. Do you have the
> > flash?
> >
> > [1]
> > https://lore.kernel.org/linux-mtd/20240603-macronix-mx25l3205d-fixups-v2-0-ff98da26835c@geanix.com/