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Date: Wed, 5 Jun 2024 15:58:13 +0200
From: Thorsten Scherer <T.Scherer@eckelmann.de>
To: Michael Walle <mwalle@kernel.org>
Cc: Tudor Ambarus <tudor.ambarus@linaro.org>, 
	Pratyush Yadav <pratyush@kernel.org>, Miquel Raynal <miquel.raynal@bootlin.com>, 
	Richard Weinberger <richard@nod.at>, Vignesh Raghavendra <vigneshr@ti.com>, 
	Rob Herring <robh@kernel.org>, Krzysztof Kozlowski <krzk+dt@kernel.org>, 
	Conor Dooley <conor+dt@kernel.org>, linux-mtd@lists.infradead.org, devicetree@vger.kernel.org, 
	linux-kernel@vger.kernel.org, 
	Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>, Marek Vasut <marex@denx.de>, Imre Kaloz <kaloz@openwrt.org>, 
	Andrew Lunn <andrew@lunn.ch>, Flavio Suligoi <f.suligoi@asem.it>, kernel@pengutronix.de
Subject: Re: [PATCH] dt-bindings: mtd: spi-nor: deprecate Everspin MRAM
 devices
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References: <20240604074231.1874972-1-mwalle@kernel.org>
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Hello,

in the past I more actively worked on the ci4x10.  That changed after switc=
hing
departments.  Anyway, I thought maybe it's useful if I share my point of vi=
ew.

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.
>=20
> Signed-off-by: Michael Walle <mwalle@kernel.org>
> Cc: Uwe Kleine-K=F6nig <u.kleine-koenig@pengutronix.de>

You cannot reach Uwe via this address anymore.

IMHO missing in this discussion is=20

    kernel@pengutronix.de

, which I added to CC.

> Cc: Thorsten Scherer <t.scherer@eckelmann.de>
> Cc: Marek Vasut <marex@denx.de>
> Cc: Imre Kaloz <kaloz@openwrt.org>
> Cc: Andrew Lunn <andrew@lunn.ch>
> Cc: Flavio Suligoi <f.suligoi@asem.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.
>=20
> 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.

My vague memory tells me (at least some of) the domain specific application=
s
running on ci4x10 rely on MTD(block?) devices.  So this change would break
user-space.

> 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.

The ci4x10 is still being used and sold.  Right now I do not have a clear
view on the implications of moving to that driver.  I'd like to invest some
time to sharpen my picture (or find the person that claims responsibility),=
 but
this will propably not happen this week.

Hope this helps.

Best regards
Thorsten

> ---
>  Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>=20
> diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml b/D=
ocumentation/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|25635=
e)|\
>                (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/eepr=
om/at25.yaml.
> +        deprecated: true
>      description:
>        SPI NOR flashes compatible with the JEDEC SFDP standard or which m=
ay be
>        identified with the READ ID opcode (0x9F) do not deserve a specifi=
c
> --=20
> 2.39.2
>=20