Previously, samsung_gpio_drection_in/output function were not covered with
one 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.
Signed-off-by: Youngmin Nam <ym0914@xxxxxxxxx>
Acked-by: Tomasz Figa <tomasz.figa@xxxxxxxxx>
---
drivers/pinctrl/samsung/pinctrl-samsung.c | 48 ++++++++++++++++++++++---------
1 file changed, 35 insertions(+), 13 deletions(-)
diff --git a/drivers/pinctrl/samsung/pinctrl-samsung.c b/drivers/pinctrl/samsung/pinctrl-samsung.c
index f67b1e9..5cc97f8 100644
--- a/drivers/pinctrl/samsung/pinctrl-samsung.c
+++ b/drivers/pinctrl/samsung/pinctrl-samsung.c
@@ -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;
}
/*
--
2.7.1
--
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