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

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Date: Fri, 21 Jun 2024 08:49:09 +0200
From: Alexander Stein <alexander.stein@...tq-group.com>
To: Tudor Ambarus <tudor.ambarus@...aro.org>, Pratyush Yadav <pratyush@...nel.org>, Michael Walle <mwalle@...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>, Michael Walle <mwalle@...nel.org>
Cc: 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

Hi everyone,

sorry for being late to the party. I just noticed this discussion while
reading [1].

Am Dienstag, 4. Juni 2024, 09:42:31 CEST schrieb Michael Walle:
> 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.

So instead of spi-nor you want to use at25 for this MRAM devices?
AFAICS at25 is a spi only driver, but spi-nor is a spi-mem driver. So I am
wondering if at25 driver is capable of using QSPI hosts.
Everspin EMxxLXB devices are capable of running in xSPI modes.
Regarding QSPI (DSPI/OSPI as well) I assumed spi-nor is a given, but maybe
I am completely wrong here. Maybe someone could clarify this.

Best regards,
Alexander

[1] https://lore.kernel.org/linux-kernel/20240405100104.480779-1-f.suligoi@asem.it/

> ---
>  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
>      description:
>        SPI NOR flashes compatible with the JEDEC SFDP standard or which may be
>        identified with the READ ID opcode (0x9F) do not deserve a specific
> 


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