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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>
This commit is contained in:
Roland Stigge 2011-02-10 15:01:23 -08:00 committed by Linus Torvalds
parent 01e05e9a90
commit 6e20fb1805
1 changed files with 22 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
drivers/gpio/pca953x.c
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@ -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.
*/