linux-kernel - Re: [PATCH v3 1/4] dt-bindings: nvmem: new optional property write-protect-gpios

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Date:   Fri, 3 Jan 2020 16:40:42 -0700
From:   Rob Herring <robh@...nel.org>
To:     Khouloud Touil <ktouil@...libre.com>
Cc:     bgolaszewski@...libre.com, mark.rutland@....com,
        srinivas.kandagatla@...aro.org, baylibre-upstreaming@...ups.io,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-i2c@...r.kernel.org, linus.walleij@...aro.org
Subject: Re: [PATCH v3 1/4] dt-bindings: nvmem: new optional property
 write-protect-gpios

On Thu, Dec 19, 2019 at 12:51:38PM +0100, Khouloud Touil wrote:
> Several memories have a write-protect pin, that when pulled high, it
> blocks the write operation.

Subject doesn't match the actual property name.

> 
> On some boards, this pin is connected to a GPIO and pulled high by
> default, which forces the user to manually change its state before
> writing.
> 
> Instead of modifying all the memory drivers to check this pin, make
> the NVMEM subsystem check if the write-protect GPIO being passed
> through the nvmem_config or defined in the device tree and pull it
> low whenever writing to the memory.
> 
> Add a new optional property to the device tree binding document, which
> allows to specify the GPIO line to which the write-protect pin is
> connected.
> 
> Signed-off-by: Khouloud Touil <ktouil@...libre.com>
> ---
>  Documentation/devicetree/bindings/nvmem/nvmem.yaml | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/nvmem/nvmem.yaml b/Documentation/devicetree/bindings/nvmem/nvmem.yaml
> index 1c75a059206c..b43c6c65294e 100644
> --- a/Documentation/devicetree/bindings/nvmem/nvmem.yaml
> +++ b/Documentation/devicetree/bindings/nvmem/nvmem.yaml
> @@ -34,6 +34,14 @@ properties:
>      description:
>        Mark the provider as read only.
>  
> +  wp-gpios:
> +    description:
> +      GPIO to which the write-protect pin of the chip is connected.
> +      The write-protect GPIO is asserted, when it's driven high
> +      (logical '1') to block the write operation. It's deasserted,
> +      when it's driven low (logical '0') to allow writing.
> +    maxItems: 1
> +
>  patternProperties:
>    "^.*@[0-9a-f]+$":
>      type: object
> @@ -63,9 +71,12 @@ patternProperties:
>  
>  examples:
>    - |
> +      #include <dt-bindings/gpio/gpio.h>
> +
>        qfprom: eeprom@...000 {
>            #address-cells = <1>;
>            #size-cells = <1>;
> +          wp-gpios = <&gpio1 3 GPIO_ACTIVE_HIGH>;
>  
>            /* ... */
>  
> -- 
> 2.17.1
>