diff options
authorBartosz Golaszewski <brgl@bgdev.pl>2017-12-19 11:28:54 +0100
committerBartosz Golaszewski <brgl@bgdev.pl>2018-01-01 19:40:50 +0100
commit6ce261e87fe14d551aae36e15171c60c823ba10a (patch)
parent3f3d8ef7f4eff5909b0cc996718de81de99af1e6 (diff)
eeprom: at24: add support for the write-protect pin
AT24 EEPROMs have a write-protect pin, which - when pulled high - inhibits writes to the upper quadrant of memory (although it has been observed that on some chips it disables writing to the entire memory range). 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. On linux this means that we either need to hog the line all the time, or set the GPIO value before writing from outside of the at24 driver. Make the driver check if the write-protect GPIO was defined in the device tree and pull it low whenever writing to the EEPROM. Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 581ba640c741..e79833d62284 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -27,6 +27,7 @@
#include <linux/regmap.h>
#include <linux/platform_data/at24.h>
#include <linux/pm_runtime.h>
+#include <linux/gpio/consumer.h>
* I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
@@ -77,6 +78,8 @@ struct at24_data {
struct nvmem_config nvmem_config;
struct nvmem_device *nvmem;
+ struct gpio_desc *wp_gpio;
* Some chips tie up multiple I2C addresses; dummy devices reserve
* them for us, and we'll use them with SMBus calls.
@@ -427,12 +430,14 @@ static int at24_write(void *priv, unsigned int off, void *val, size_t count)
* from this host, but not from other I2C masters.
+ gpiod_set_value_cansleep(at24->wp_gpio, 0);
while (count) {
int status;
status = at24_regmap_write(at24, buf, off, count);
if (status < 0) {
+ gpiod_set_value_cansleep(at24->wp_gpio, 1);
return status;
@@ -442,6 +447,7 @@ static int at24_write(void *priv, unsigned int off, void *val, size_t count)
count -= status;
+ gpiod_set_value_cansleep(at24->wp_gpio, 1);
@@ -573,6 +579,11 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
at24->num_addresses = num_addresses;
at24->offset_adj = at24_get_offset_adj(chip.flags, chip.byte_len);
+ at24->wp_gpio = devm_gpiod_get_optional(&client->dev,
+ "wp", GPIOD_OUT_HIGH);
+ if (IS_ERR(at24->wp_gpio))
+ return PTR_ERR(at24->wp_gpio);
at24->client[0].client = client;
at24->client[0].regmap = devm_regmap_init_i2c(client, &regmap_config);
if (IS_ERR(at24->client[0].regmap))

Privacy Policy