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Commit 6e20fb18 authored by Roland Stigge's avatar Roland Stigge Committed by Linus Torvalds
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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: default avatarRoland Stigge <stigge@antcom.de>
Acked-by: default avatarEric 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 01e05e9a

drivers/gpio/pca953x.c

+22 −6
Original line number Diff line number Diff line
@@ -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.

	 */