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authorRoland Stigge <stigge@antcom.de>2011-02-10 15:01:23 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-02-11 16:12:20 -0800
commit6e20fb18054c179d7e64c0af43d855b9310a3394 (patch)
tree7fe6eda33162dbeab61afc2392229b9c57a644f1 /drivers
parent01e05e9a90b8f4c3997ae0537e87720eb475e532 (diff)
drivers/gpio/pca953x.c: add a mutex to fix race condition
Add a mutex to register communication and handling. Without the mutex, GPIOs didn't switch as expected when toggled in a fast sequence of status changes of multiple outputs. Signed-off-by: Roland Stigge <stigge@antcom.de> Acked-by: Eric Miao <eric.y.miao@gmail.com> Cc: Grant Likely <grant.likely@secretlab.ca> Cc: Marc Zyngier <maz@misterjones.org> Cc: Ben Gardner <bgardner@wabtec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/gpio/pca953x.c28
1 files changed, 22 insertions, 6 deletions
diff --git a/drivers/gpio/pca953x.c b/drivers/gpio/pca953x.c
index a261972f603..b473429eee7 100644
--- a/drivers/gpio/pca953x.c
+++ b/drivers/gpio/pca953x.c
@@ -60,6 +60,7 @@ struct pca953x_chip {
unsigned gpio_start;
uint16_t reg_output;
uint16_t reg_direction;
+ struct mutex i2c_lock;
#ifdef CONFIG_GPIO_PCA953X_IRQ
struct mutex irq_lock;
@@ -119,13 +120,17 @@ static int pca953x_gpio_direction_input(struct gpio_chip *gc, unsigned off)
chip = container_of(gc, struct pca953x_chip, gpio_chip);
+ mutex_lock(&chip->i2c_lock);
reg_val = chip->reg_direction | (1u << off);
ret = pca953x_write_reg(chip, PCA953X_DIRECTION, reg_val);
if (ret)
- return ret;
+ goto exit;
chip->reg_direction = reg_val;
- return 0;
+ ret = 0;
+exit:
+ mutex_unlock(&chip->i2c_lock);
+ return ret;
}
static int pca953x_gpio_direction_output(struct gpio_chip *gc,
@@ -137,6 +142,7 @@ static int pca953x_gpio_direction_output(struct gpio_chip *gc,
chip = container_of(gc, struct pca953x_chip, gpio_chip);
+ mutex_lock(&chip->i2c_lock);
/* set output level */
if (val)
reg_val = chip->reg_output | (1u << off);
@@ -145,7 +151,7 @@ static int pca953x_gpio_direction_output(struct gpio_chip *gc,
ret = pca953x_write_reg(chip, PCA953X_OUTPUT, reg_val);
if (ret)
- return ret;
+ goto exit;
chip->reg_output = reg_val;
@@ -153,10 +159,13 @@ static int pca953x_gpio_direction_output(struct gpio_chip *gc,
reg_val = chip->reg_direction & ~(1u << off);
ret = pca953x_write_reg(chip, PCA953X_DIRECTION, reg_val);
if (ret)
- return ret;
+ goto exit;
chip->reg_direction = reg_val;
- return 0;
+ ret = 0;
+exit:
+ mutex_unlock(&chip->i2c_lock);
+ return ret;
}
static int pca953x_gpio_get_value(struct gpio_chip *gc, unsigned off)
@@ -167,7 +176,9 @@ static int pca953x_gpio_get_value(struct gpio_chip *gc, unsigned off)
chip = container_of(gc, struct pca953x_chip, gpio_chip);
+ mutex_lock(&chip->i2c_lock);
ret = pca953x_read_reg(chip, PCA953X_INPUT, &reg_val);
+ mutex_unlock(&chip->i2c_lock);
if (ret < 0) {
/* NOTE: diagnostic already emitted; that's all we should
* do unless gpio_*_value_cansleep() calls become different
@@ -187,6 +198,7 @@ static void pca953x_gpio_set_value(struct gpio_chip *gc, unsigned off, int val)
chip = container_of(gc, struct pca953x_chip, gpio_chip);
+ mutex_lock(&chip->i2c_lock);
if (val)
reg_val = chip->reg_output | (1u << off);
else
@@ -194,9 +206,11 @@ static void pca953x_gpio_set_value(struct gpio_chip *gc, unsigned off, int val)
ret = pca953x_write_reg(chip, PCA953X_OUTPUT, reg_val);
if (ret)
- return;
+ goto exit;
chip->reg_output = reg_val;
+exit:
+ mutex_unlock(&chip->i2c_lock);
}
static void pca953x_setup_gpio(struct pca953x_chip *chip, int gpios)
@@ -517,6 +531,8 @@ static int __devinit pca953x_probe(struct i2c_client *client,
chip->names = pdata->names;
+ mutex_init(&chip->i2c_lock);
+
/* initialize cached registers from their original values.
* we can't share this chip with another i2c master.
*/