linux-kernel - Re: [PATCH v5 1/5] mtd: spi-nor: core: add manufacturer flags

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Message-ID: <4e0cf43c-4843-451c-ac6f-86775dbccb2b@linaro.org>
Date: Mon, 23 Sep 2024 07:04:22 +0100
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: Erez Geva <erezgeva@...ime.org>, linux-mtd@...ts.infradead.org,
 Pratyush Yadav <pratyush@...nel.org>, Michael Walle <mwalle@...nel.org>
Cc: 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>, Esben Haabendal <esben@...nix.com>,
 Erez Geva <ErezGeva2@...il.com>
Subject: Re: [PATCH v5 1/5] mtd: spi-nor: core: add manufacturer flags

Hi,

On 9/20/24 7:12 PM, Erez Geva wrote:
> From: Erez Geva <ErezGeva2@...il.com>
> 
> Add flag for always trying reading SFDP:
> Some vendors reuse all JEDEC IDs on manufacture table
>  with new chips that support SFDP.
> 
> Add flag for reading OTP parameters from device tree.
> Some vendors reuse JEDEC IDs
>  with several chips with different OTP parameters.
> Alternatively we read parameters from SFDP.
> But the OTP parameters are absent from the SFDP.

Do you have some specific flashes that you try to identify? Why can't
they be differentiated at runtime?

> So there is not other way but to add the OTP parameters in the device tree.
> 

If there isn't any way to distinguish the flashes at runtime (which I
doubt/challenge btw), then as a last resort we introduce a dedicated
compatible for the flash in cause and specify all needed parameters in a
dedicated flash entry. This shall be more generic as further flash
parameters can be statically specified in the dedicated flash entry,
less invasive for dt, and less confusing for people when they decide
whether to use OTP or not. OTP params in device tree is a no-go.

But again, you have to prove why you can't distinguish the flash at
runtime before introducing a new flash compatible. So don't go this path
before sharing with us what you're trying to achieve.

Cheers,
ta