pinctrl: samsung: Fixes samsung_gpio_direction_in/output releated with spinlock

PATCH Superseded Youngmin Nam 3 participants 4 messages Jan 24, 2016 – Feb 8, 2016

Subsystems (3)

Arm Samsung Exynos Pin control Pin controller - Samsung

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Youngmin Nam

author

2016-01-24 06:04 UTC #0 lore raw

PATCH v2 1/1 pinctrl: samsung: Fixes samsung_gpio_direction_in/output releated with spinlock

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 <[email protected]>

---
 drivers/pinctrl/samsung/pinctrl-samsung.c | 48 ++++++++++++++++++++++---------
 1 file changed, 35 insertions(+), 13 deletions(-)

drivers/pinctrl/samsung/pinctrl-samsung.c +35 ~~-13~~

index 48294e7..c5828b8 100644
@@ -519,25 +519,35 @@ 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 = gc_to_pin_bank(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 = gc_to_pin_bank(gc);
+	unsigned long flags;
 
+	spin_lock_irqsave(&bank->slock, flags);
+	samsung_gpio_set_value(gc, offset, value);
 	spin_unlock_irqrestore(&bank->slock, flags);
 }

@@ -558,6 +568,8 @@ 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.
  */

@@ -569,7 +581,6 @@ 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 = gc_to_pin_bank(gc);
 	type = bank->type;

@@ -586,31 +597,42 @@ 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 = gc_to_pin_bank(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 = gc_to_pin_bank(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;
 }
 
 /*

Signature · 1 line

2.7.0.25.gfc10eb5

Linus Walleij

2016-01-27 12:36 UTC #1 lore raw

Quoted 21 lines · Youngmin Nam

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.

Quoted 7 lines

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 <[email protected]>

This patch does not apply to v4.5-rc1. Please rebase this and resend. (With Thomas ACK if it's valid.)

Yours,
Linus Walleij

Youngmin Nam

author

2016-02-08 04:03 UTC #2 lore raw

Thanks Linus and Tomasz.

Sorry for late. I will rebase on v4.5-rc3 and resend.

Thanks.

Quoted 37 lines · Linus Walleij

Quoted 21 lines · Youngmin Nam
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.
Quoted 7 lines
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 <[email protected]>
This patch does not apply to v4.5-rc1. Please rebase this and resend. (With Thomas ACK if it's valid.)
Yours,
Linus Walleij

Tomasz Figa

Acked-by on v2 1/1

2016-01-27 13:51 UTC #3 lore raw

In reply to Youngmin Nam

Hi Youngmin,

2016-01-24 15:02 GMT+09:00 Youngmin Nam <[email protected]>:

Quoted 24 lines

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.

Quoted 8 lines

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 <[email protected]>
---
 drivers/pinctrl/samsung/pinctrl-samsung.c | 48 ++++++++++++++++++++++---------
 1 file changed, 35 insertions(+), 13 deletions(-)

Thanks for addressing my comments.

Acked-by Tomasz Figa <[email protected]>

However please rebase as Linus suggested.

Best regards,
Tomasz