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Message-ID: <1bd281d8-a576-26dc-79c3-b1a72a4a9691@linaro.org>
Date:   Thu, 17 Feb 2022 11:01:21 +0000
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Subject: Re: [PATCH v2 3/4] nvmem: core: Fix a conflict between MTD and NVMEM
 on wp-gpios property
Content-Language: en-US
To:     Christophe Kerello <christophe.kerello@foss.st.com>,
        miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com,
        robh+dt@kernel.org
Cc:     linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-stm32@st-md-mailman.stormreply.com,
        devicetree@vger.kernel.org, chenshumin86@sina.com
References: <20220131095755.8981-1-christophe.kerello@foss.st.com>
 <20220131095755.8981-4-christophe.kerello@foss.st.com>
From:   Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
In-Reply-To: <20220131095755.8981-4-christophe.kerello@foss.st.com>
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On 31/01/2022 09:57, Christophe Kerello wrote:
> Wp-gpios property can be used on NVMEM nodes and the same property can
> be also used on MTD NAND nodes. In case of the wp-gpios property is
> defined at NAND level node, the GPIO management is done at NAND driver
> level. Write protect is disabled when the driver is probed or resumed
> and is enabled when the driver is released or suspended.
> 
> When no partitions are defined in the NAND DT node, then the NAND DT node
> will be passed to NVMEM framework. If wp-gpios property is defined in
> this node, the GPIO resource is taken twice and the NAND controller
> driver fails to probe.
> 
> It would be possible to set config->wp_gpio at MTD level before calling
> nvmem_register function but NVMEM framework will toggle this GPIO on
> each write when this GPIO should only be controlled at NAND level driver
> to ensure that the Write Protect has not been enabled.
> 
> A way to fix this conflict is to add a new boolean flag in nvmem_config
> named skip_wp_gpio. In case skip_wp_gpio is set, the GPIO resource will
> be managed by the provider.
> 
> Signed-off-by: Christophe Kerello <christophe.kerello@foss.st.com>
> ---
> Changes in v2:
>   - rework the proposal done to fix a conflict between MTD and NVMEM on
>     wp-gpios property.
> 
>   drivers/nvmem/core.c           | 2 +-
>   include/linux/nvmem-provider.h | 4 +++-
>   2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index 23a38dcf0fc4..cb40dca6a51d 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -771,7 +771,7 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
>   
>   	if (config->wp_gpio)
>   		nvmem->wp_gpio = config->wp_gpio;
> -	else
> +	else if (!config->skip_wp_gpio)
>   		nvmem->wp_gpio = gpiod_get_optional(config->dev, "wp",
>   						    GPIOD_OUT_HIGH);
>   	if (IS_ERR(nvmem->wp_gpio)) {
> diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
> index 98efb7b5660d..4b480023c265 100644
> --- a/include/linux/nvmem-provider.h
> +++ b/include/linux/nvmem-provider.h
> @@ -70,7 +70,8 @@ struct nvmem_keepout {
>    * @word_size:	Minimum read/write access granularity.
>    * @stride:	Minimum read/write access stride.
>    * @priv:	User context passed to read/write callbacks.
> - * @wp-gpio:   Write protect pin
> + * @wp-gpio:	Write protect pin
> + * @skip_wp_gpio: Write Protect pin is managed by the provider.

Can we rename this to ingore_wp as suggested by Miquel.

--srini

>    *
>    * Note: A default "nvmem<id>" name will be assigned to the device if
>    * no name is specified in its configuration. In such case "<id>" is
> @@ -92,6 +93,7 @@ struct nvmem_config {
>   	enum nvmem_type		type;
>   	bool			read_only;
>   	bool			root_only;
> +	bool			skip_wp_gpio;
>   	struct device_node	*of_node;
>   	bool			no_of_node;
>   	nvmem_reg_read_t	reg_read;