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pinctrl: samsung: fix SMP race condition

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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: Youngmin Nam <ym0914@gmail.com>
Acked-by: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Youngmin Nam 2016-02-09 00:49:28 +09:00 committed by Linus Walleij
parent 7864d92621
commit d9ff0eb9ca
1 changed files with 35 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
drivers/pinctrl/samsung/pinctrl-samsung.c
View File

@ -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;
}
/*