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Commit d9ff0eb9 authored by Youngmin Nam's avatar Youngmin Nam Committed by Linus Walleij
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pinctrl: samsung: fix SMP race condition 



Previously, samsung_gpio_drection_in/output function were not covered
with a spinlock.

For example, samsung_gpio_direction_output function consists of
two functions.
1. samsung_gpio_set
2. samsung_gpio_set_direction

When 2 CPUs try to control the same gpio pin heavily,
(situation like i2c control with gpio emulation)
This situation can cause below problem.

CPU 0                                   | CPU1
                                        |
samsung_gpio_direction_output           |
   samsung_gpio_set(pin A as 1)         | samsung_gpio_direction_output
                                        |    samsung_gpio_set(pin A as 0)
   samsung_gpio_set_direction           |
                                        |    samsung_gpio_set_direction

The initial value of pin A will be set as 0 while we wanted to set pin A as 1.

This patch modifies samsung_gpio_direction_in/output function
to be done in one spinlock to fix race condition.

Additionally, the new samsung_gpio_set_value was added to implement
gpio set callback(samsung_gpio_set) with spinlock using this function.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarYoungmin Nam <ym0914@gmail.com>
Acked-by: default avatarTomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent 7864d926

drivers/pinctrl/samsung/pinctrl-samsung.c

+35 −13
Original line number Diff line number Diff line
@@ -514,25 +514,35 @@ static const struct pinconf_ops samsung_pinconf_ops = { 
	.pin_config_group_set	= samsung_pinconf_group_set,

};



/* gpiolib gpio_set callback function */

static void samsung_gpio_set(struct gpio_chip *gc, unsigned offset, int value)

/*

 * The samsung_gpio_set_vlaue() should be called with "bank->slock" held

 * to avoid race condition.

 */

static void samsung_gpio_set_value(struct gpio_chip *gc,

					  unsigned offset, int value)

{

	struct samsung_pin_bank *bank = gpiochip_get_data(gc);

	const struct samsung_pin_bank_type *type = bank->type;

	unsigned long flags;

	void __iomem *reg;

	u32 data;



	reg = bank->drvdata->virt_base + bank->pctl_offset;



	spin_lock_irqsave(&bank->slock, flags);



	data = readl(reg + type->reg_offset[PINCFG_TYPE_DAT]);

	data &= ~(1 << offset);

	if (value)

		data |= 1 << offset;

	writel(data, reg + type->reg_offset[PINCFG_TYPE_DAT]);

}



/* gpiolib gpio_set callback function */

static void samsung_gpio_set(struct gpio_chip *gc, unsigned offset, int value)

{

	struct samsung_pin_bank *bank = gpiochip_get_data(gc);

	unsigned long flags;



	spin_lock_irqsave(&bank->slock, flags);

	samsung_gpio_set_value(gc, offset, value);

	spin_unlock_irqrestore(&bank->slock, flags);

}
@@ -553,6 +563,8 @@ static int samsung_gpio_get(struct gpio_chip *gc, unsigned offset) 
}



/*

 * The samsung_gpio_set_direction() should be called with "bank->slock" held

 * to avoid race condition.

 * The calls to gpio_direction_output() and gpio_direction_input()

 * leads to this function call.

 */
@@ -564,7 +576,6 @@ static int samsung_gpio_set_direction(struct gpio_chip *gc, 
	struct samsung_pinctrl_drv_data *drvdata;

	void __iomem *reg;

	u32 data, mask, shift;

	unsigned long flags;



	bank = gpiochip_get_data(gc);

	type = bank->type;
@@ -581,31 +592,42 @@ static int samsung_gpio_set_direction(struct gpio_chip *gc, 
		reg += 4;

	}



	spin_lock_irqsave(&bank->slock, flags);



	data = readl(reg);

	data &= ~(mask << shift);

	if (!input)

		data |= FUNC_OUTPUT << shift;

	writel(data, reg);



	spin_unlock_irqrestore(&bank->slock, flags);



	return 0;

}



/* gpiolib gpio_direction_input callback function. */

static int samsung_gpio_direction_input(struct gpio_chip *gc, unsigned offset)

{

	return samsung_gpio_set_direction(gc, offset, true);

	struct samsung_pin_bank *bank = gpiochip_get_data(gc);

	unsigned long flags;

	int ret;



	spin_lock_irqsave(&bank->slock, flags);

	ret = samsung_gpio_set_direction(gc, offset, true);

	spin_unlock_irqrestore(&bank->slock, flags);

	return ret;

}



/* gpiolib gpio_direction_output callback function. */

static int samsung_gpio_direction_output(struct gpio_chip *gc, unsigned offset,

							int value)

{

	samsung_gpio_set(gc, offset, value);

	return samsung_gpio_set_direction(gc, offset, false);

	struct samsung_pin_bank *bank = gpiochip_get_data(gc);

	unsigned long flags;

	int ret;



	spin_lock_irqsave(&bank->slock, flags);

	samsung_gpio_set_value(gc, offset, value);

	ret = samsung_gpio_set_direction(gc, offset, false);

	spin_unlock_irqrestore(&bank->slock, flags);



	return ret;

}



/*