linux-kernel - Re: [PATCH] dt-bindings: mtd: spi-nor: deprecate Everspin MRAM devices

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Message-ID: <20240604-ladylike-gout-6fd6ae992712@spud>
Date: Tue, 4 Jun 2024 18:01:23 +0100
From: Conor Dooley <conor@...nel.org>
To: Michael Walle <mwalle@...nel.org>
Cc: Tudor Ambarus <tudor.ambarus@...aro.org>,
	Pratyush Yadav <pratyush@...nel.org>,
	Miquel Raynal <miquel.raynal@...tlin.com>,
	Richard Weinberger <richard@....at>,
	Vignesh Raghavendra <vigneshr@...com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-mtd@...ts.infradead.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	Thorsten Scherer <t.scherer@...elmann.de>,
	Marek Vasut <marex@...x.de>, Imre Kaloz <kaloz@...nwrt.org>,
	Andrew Lunn <andrew@...n.ch>, Flavio Suligoi <f.suligoi@...m.it>
Subject: Re: [PATCH] dt-bindings: mtd: spi-nor: deprecate Everspin MRAM
 devices

On Tue, Jun 04, 2024 at 09:42:31AM +0200, Michael Walle wrote:
> These devices are more like an AT25 compatible EEPROM instead of
> flashes. Like an EEPROM the user doesn't need to explicitly erase the
> memory, nor are there sectors or pages. Thus, instead of the SPI-NOR
> (flash) driver, one should instead use the at25 EEPROM driver.
> 
> Signed-off-by: Michael Walle <mwalle@...nel.org>
> Cc: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> Cc: Thorsten Scherer <t.scherer@...elmann.de>
> Cc: Marek Vasut <marex@...x.de>
> Cc: Imre Kaloz <kaloz@...nwrt.org>
> Cc: Andrew Lunn <andrew@...n.ch>
> Cc: Flavio Suligoi <f.suligoi@...m.it>
> ---
> The referenced binding only supports the true AT25 compatible EEPROMs
> where you have to specify additional properties like size and page size
> or cypress FRAM devices where all the properties are discovered by the
> driver. I don't have the actual hardware, therefore I can't work on a
> proper driver and binding. But I really want to deprecate the use of
> these EEPROM like devices in SPI-NOR. So as a first step, mark the
> devices in the DT bindings as deprecated.
> 
> There are three in-tree users of this. I hope I've CCed all the relevant
> people. With the switch to the at25 driver also comes a user-space
> facing change: there is no more MTD device. Instead there is an "eeprom"
> file in /sys now, just like for every other EEPROM.
> 
> Marek already expressed, that the sps1 dts can likely be removed
> altogether. I'd like to hear from the other board DTS maintainers if
> they seem some problems moving to the EEPROM interface - or maybe that
> device isn't used at all anyway. So in the end, we can hopefully move
> all the users over to the at25 driver.
> ---
>  Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
> index 6e3afb42926e..2dccb6b049ea 100644
> --- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
> +++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
> @@ -21,7 +21,6 @@ properties:
>                (m25p(40|80|16|32|64|128)|\
>                n25q(32b|064|128a11|128a13|256a|512a|164k)))|\
>                atmel,at25df(321a|641|081a)|\
> -              everspin,mr25h(10|40|128|256)|\
>                (mxicy|macronix),mx25l(4005a|1606e|6405d|8005|12805d|25635e)|\
>                (mxicy|macronix),mx25u(4033|4035)|\
>                (spansion,)?s25fl(128s|256s1|512s|008k|064k|164k)|\
> @@ -42,6 +41,14 @@ properties:
>                - spansion,s25fs512s
>            - const: jedec,spi-nor
>        - const: jedec,spi-nor
> +
> +      # Deprecated bindings
> +      - items:
> +          - pattern: "^everspin,mr25h(10|40|128|256)$"
> +          - const: jedec,spi-nor
> +        description:
> +          Deprecated binding, use Documentation/devicetree/bindings/eeprom/at25.yaml.
> +        deprecated: true

The idea here seems okay, but directing people to use the at25 binding,
without actually documenting the replacement compatibles etc is far from
ideal. I think even a wording change that points out that that these
devices need to be documented in that file would be an improvement, the
current wording makes it seem like the works been done.
Until there's a replacement driver, I don't think you could really
expect anyone to move to a new binding anyway.

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