From 2a127da461a9d8d97782d6e82b227041393eb4d2 Mon Sep 17 00:00:00 2001
From: Khouloud Touil <ktouil@baylibre.com>
Date: Tue, 7 Jan 2020 10:29:19 +0100
Subject: [PATCH] nvmem: add support for the write-protect pin
The write-protect pin handling looks like a standard property that
could benefit other users if available in the core nvmem framework.
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.
There was a suggestion for introducing the gpiodesc from pdata, but
as pdata is already removed it could be replaced by adding it to
nvmem_config.
Reference: https://lists.96boards.org/pipermail/dev/2018-August/001056.html
Signed-off-by: Khouloud Touil <ktouil@baylibre.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
drivers/nvmem/core.c | 19 +++++++++++++++++--
drivers/nvmem/nvmem.h | 2 ++
include/linux/nvmem-provider.h | 3 +++
3 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 9f1ee9c766eca..3e1c94c4eee8c 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -15,6 +15,7 @@
#include <linux/module.h>
#include <linux/nvmem-consumer.h>
#include <linux/nvmem-provider.h>
+#include <linux/gpio/consumer.h>
#include <linux/of.h>
#include <linux/slab.h>
#include "nvmem.h"
@@ -54,8 +55,14 @@ static int nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
static int nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset,
void *val, size_t bytes)
{
- if (nvmem->reg_write)
- return nvmem->reg_write(nvmem->priv, offset, val, bytes);
+ int ret;
+
+ if (nvmem->reg_write) {
+ gpiod_set_value_cansleep(nvmem->wp_gpio, 0);
+ ret = nvmem->reg_write(nvmem->priv, offset, val, bytes);
+ gpiod_set_value_cansleep(nvmem->wp_gpio, 1);
+ return ret;
+ }
return -EINVAL;
}
@@ -338,6 +345,14 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
kfree(nvmem);
return ERR_PTR(rval);
}
+ if (config->wp_gpio)
+ nvmem->wp_gpio = config->wp_gpio;
+ else
+ nvmem->wp_gpio = gpiod_get_optional(config->dev, "wp",
+ GPIOD_OUT_HIGH);
+ if (IS_ERR(nvmem->wp_gpio))
+ return PTR_ERR(nvmem->wp_gpio);
+
kref_init(&nvmem->refcnt);
INIT_LIST_HEAD(&nvmem->cells);
diff --git a/drivers/nvmem/nvmem.h b/drivers/nvmem/nvmem.h
index eb8ed7121fa3a..be0d66d75c8aa 100644
--- a/drivers/nvmem/nvmem.h
+++ b/drivers/nvmem/nvmem.h
@@ -9,6 +9,7 @@
#include <linux/list.h>
#include <linux/nvmem-consumer.h>
#include <linux/nvmem-provider.h>
+#include <linux/gpio/consumer.h>
struct nvmem_device {
struct module *owner;
@@ -26,6 +27,7 @@ struct nvmem_device {
struct list_head cells;
nvmem_reg_read_t reg_read;
nvmem_reg_write_t reg_write;
+ struct gpio_desc *wp_gpio;
void *priv;
};
diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
index fe051323be0a2..6d6f8e5d24c97 100644
--- a/include/linux/nvmem-provider.h
+++ b/include/linux/nvmem-provider.h
@@ -11,6 +11,7 @@
#include <linux/err.h>
#include <linux/errno.h>
+#include <linux/gpio/consumer.h>
struct nvmem_device;
struct nvmem_cell_info;
@@ -45,6 +46,7 @@ enum nvmem_type {
* @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
*
* 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
@@ -58,6 +60,7 @@ struct nvmem_config {
const char *name;
int id;
struct module *owner;
+ struct gpio_desc *wp_gpio;
const struct nvmem_cell_info *cells;
int ncells;
enum nvmem_type type;