linux-kernel - Re: [PATCH v3 1/2] dt-bindings: mtd: jedec, spi-nor: Add DT property to avoid setting SRWD bit in status register

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Message-ID: <20230626-stonework-freely-bec6f8bc83e6@spud>
Date:   Mon, 26 Jun 2023 18:23:56 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>
Cc:     tudor.ambarus@...aro.org, pratyush@...nel.org,
        miquel.raynal@...tlin.com, richard@....at, vigneshr@...com,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, git@....com, michael@...le.cc,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, amitrkcian2002@...il.com
Subject: Re: [PATCH v3 1/2] dt-bindings: mtd: jedec, spi-nor: Add DT property
 to avoid setting SRWD bit in status register

On Sun, Jun 25, 2023 at 03:32:50PM +0530, Amit Kumar Mahapatra wrote:
> If the WP# signal of the flash device is either not connected or is wrongly
> tied to GND (that includes internal pull-downs), and the software sets the
> status register write disable (SRWD) bit in the status register then the
> status register permanently becomes read-only. To avoid this added a new
> boolean DT property "no-wp". If this property is set in the DT then the
> software avoids setting the SRWD during status register write operation.
> 
> Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>
> ---
> As the DT property name has changed so, removed Reviewed-by tag.
> @Cornor if possible, could you please review this updated patch.

Rob was the one who objected to the property name.
Old & new names are fine by me, it was the text I think I cared about.
Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>

Thanks for actually explaining why you dropped the tag,
Conor.

> ---
>  .../devicetree/bindings/mtd/jedec,spi-nor.yaml    | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
> index 89959e5c47ba..97344969b02d 100644
> --- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
> +++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
> @@ -70,6 +70,21 @@ properties:
>        be used on such systems, to denote the absence of a reliable reset
>        mechanism.
>  
> +  no-wp:
> +    type: boolean
> +    description:
> +      The status register write disable (SRWD) bit in status register, combined
> +      with the WP# signal, provides hardware data protection for the device. When
> +      the SRWD bit is set to 1, and the WP# signal is either driven LOW or hard
> +      strapped to LOW, the status register nonvolatile bits become read-only and
> +      the WRITE STATUS REGISTER operation will not execute. The only way to exit
> +      this hardware-protected mode is to drive WP# HIGH. If the WP# signal of the
> +      flash device is not connected or is wrongly tied to GND (that includes internal
> +      pull-downs) then status register permanently becomes read-only as the SRWD bit
> +      cannot be reset. This boolean flag can be used on such systems to avoid setting
> +      the SRWD bit while writing the status register. WP# signal hard strapped to GND
> +      can be a valid use case.
> +
>    reset-gpios:
>      description:
>        A GPIO line connected to the RESET (active low) signal of the device.
> -- 
> 2.17.1
> 

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