linux-kernel - [PATCH 3/3] nvmem: core: Fix a conflict between MTD and NVMEM on wp-gpios property

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Message-ID: <20220105135734.271313-4-christophe.kerello@foss.st.com>
Date:   Wed, 5 Jan 2022 14:57:34 +0100
From:   Christophe Kerello <christophe.kerello@...s.st.com>
To:     <miquel.raynal@...tlin.com>, <richard@....at>, <vigneshr@...com>,
        <robh+dt@...nel.org>, <srinivas.kandagatla@...aro.org>
CC:     <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <devicetree@...r.kernel.org>, <chenshumin86@...a.com>,
        Christophe Kerello <christophe.kerello@...s.st.com>
Subject: [PATCH 3/3] nvmem: core: Fix a conflict between MTD and NVMEM on wp-gpios property

Wp-gpios property can be used on NVMEN 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 toggled 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.

As MTD framework is only using NVMEN framework in read only, a way to fix
this conflict is to get the GPIO resource at NVMEM level only if reg_write
API is defined. This GPIO is only toggled if reg_write ops is defined.

Signed-off-by: Christophe Kerello <christophe.kerello@...s.st.com>
---
 drivers/nvmem/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index e765d3d0542e..e11c74db64f9 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -769,7 +769,7 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)

 	if (config->wp_gpio)
 		nvmem->wp_gpio = config->wp_gpio;
-	else
+	else if (config->reg_write)
 		nvmem->wp_gpio = gpiod_get_optional(config->dev, "wp",
 						    GPIOD_OUT_HIGH);
 	if (IS_ERR(nvmem->wp_gpio)) {
-- 
2.25.1