Commit 2559f2e0 authored by Bartosz Golaszewski's avatar Bartosz Golaszewski
Browse files

gpio: reinforce desc->flags handling 



We now removed the gpio_lock spinlock and modified the places
previously protected by it to handle desc->flags access in a consistent
way. Let's improve other places that were previously unprotected by
reading the flags field of gpio_desc once and using the stored value for
logic consistency. If we need to modify the field, let's also write it
back once with a consistent value resulting from the function's logic.

Signed-off-by: default avatarBartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Acked-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
parent 35b54533

drivers/gpio/gpiolib.c

+25 −17
Original line number Diff line number Diff line
@@ -336,18 +336,20 @@ static int gpiochip_find_base_unlocked(int ngpio) 
int gpiod_get_direction(struct gpio_desc *desc)

{

	struct gpio_chip *gc;

	unsigned long flags;

	unsigned int offset;

	int ret;



	gc = gpiod_to_chip(desc);

	offset = gpio_chip_hwgpio(desc);

	flags = READ_ONCE(desc->flags);



	/*

	 * Open drain emulation using input mode may incorrectly report

	 * input here, fix that up.

	 */

	if (test_bit(FLAG_OPEN_DRAIN, &desc->flags) &&

	    test_bit(FLAG_IS_OUT, &desc->flags))

	if (test_bit(FLAG_OPEN_DRAIN, &flags) &&

	    test_bit(FLAG_IS_OUT, &flags))

		return 0;



	if (!gc->get_direction)
@@ -361,7 +363,8 @@ int gpiod_get_direction(struct gpio_desc *desc) 
	if (ret > 0)

		ret = 1;



	assign_bit(FLAG_IS_OUT, &desc->flags, !ret);

	assign_bit(FLAG_IS_OUT, &flags, !ret);

	WRITE_ONCE(desc->flags, flags);



	return ret;

}
@@ -751,9 +754,6 @@ static void gpiochip_machine_hog(struct gpio_chip *gc, struct gpiod_hog *hog) 
		return;

	}



	if (test_bit(FLAG_IS_HOGGED, &desc->flags))

		return;



	rv = gpiod_hog(desc, hog->line_name, hog->lflags, hog->dflags);

	if (rv)

		gpiod_err(desc, "%s: unable to hog GPIO line (%s:%u): %d\n",
@@ -2528,13 +2528,16 @@ static int gpio_set_config(struct gpio_desc *desc, enum pin_config_param mode) 
static int gpio_set_bias(struct gpio_desc *desc)

{

	enum pin_config_param bias;

	unsigned long flags;

	unsigned int arg;



	if (test_bit(FLAG_BIAS_DISABLE, &desc->flags))

	flags = READ_ONCE(desc->flags);



	if (test_bit(FLAG_BIAS_DISABLE, &flags))

		bias = PIN_CONFIG_BIAS_DISABLE;

	else if (test_bit(FLAG_PULL_UP, &desc->flags))

	else if (test_bit(FLAG_PULL_UP, &flags))

		bias = PIN_CONFIG_BIAS_PULL_UP;

	else if (test_bit(FLAG_PULL_DOWN, &desc->flags))

	else if (test_bit(FLAG_PULL_DOWN, &flags))

		bias = PIN_CONFIG_BIAS_PULL_DOWN;

	else

		return 0;
@@ -2700,24 +2703,28 @@ EXPORT_SYMBOL_GPL(gpiod_direction_output_raw); 
 */

int gpiod_direction_output(struct gpio_desc *desc, int value)

{

	unsigned long flags;

	int ret;



	VALIDATE_DESC(desc);

	if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))



	flags = READ_ONCE(desc->flags);



	if (test_bit(FLAG_ACTIVE_LOW, &flags))

		value = !value;

	else

		value = !!value;



	/* GPIOs used for enabled IRQs shall not be set as output */

	if (test_bit(FLAG_USED_AS_IRQ, &desc->flags) &&

	    test_bit(FLAG_IRQ_IS_ENABLED, &desc->flags)) {

	if (test_bit(FLAG_USED_AS_IRQ, &flags) &&

	    test_bit(FLAG_IRQ_IS_ENABLED, &flags)) {

		gpiod_err(desc,

			  "%s: tried to set a GPIO tied to an IRQ as output\n",

			  __func__);

		return -EIO;

	}



	if (test_bit(FLAG_OPEN_DRAIN, &desc->flags)) {

	if (test_bit(FLAG_OPEN_DRAIN, &flags)) {

		/* First see if we can enable open drain in hardware */

		ret = gpio_set_config(desc, PIN_CONFIG_DRIVE_OPEN_DRAIN);

		if (!ret)
@@ -2727,7 +2734,7 @@ int gpiod_direction_output(struct gpio_desc *desc, int value) 
			ret = gpiod_direction_input(desc);

			goto set_output_flag;

		}

	} else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags)) {

	} else if (test_bit(FLAG_OPEN_SOURCE, &flags)) {

		ret = gpio_set_config(desc, PIN_CONFIG_DRIVE_OPEN_SOURCE);

		if (!ret)

			goto set_output_value;
@@ -4424,21 +4431,22 @@ int gpiod_hog(struct gpio_desc *desc, const char *name, 
	int hwnum;

	int ret;



	if (test_and_set_bit(FLAG_IS_HOGGED, &desc->flags))

		return 0;



	gc = gpiod_to_chip(desc);

	hwnum = gpio_chip_hwgpio(desc);



	local_desc = gpiochip_request_own_desc(gc, hwnum, name,

					       lflags, dflags);

	if (IS_ERR(local_desc)) {

		clear_bit(FLAG_IS_HOGGED, &desc->flags);

		ret = PTR_ERR(local_desc);

		pr_err("requesting hog GPIO %s (chip %s, offset %d) failed, %d\n",

		       name, gc->label, hwnum, ret);

		return ret;

	}



	/* Mark GPIO as hogged so it can be identified and removed later */

	set_bit(FLAG_IS_HOGGED, &desc->flags);



	gpiod_dbg(desc, "hogged as %s%s\n",

		(dflags & GPIOD_FLAGS_BIT_DIR_OUT) ? "output" : "input",

		(dflags & GPIOD_FLAGS_BIT_DIR_OUT) ?