linux-kernel - [PATCH RFT 2/2] gpio: gpio-pch: Use spinlock for register access protection

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Date:	Sun, 29 Jul 2012 10:55:54 +0800
From:	Axel Lin <axel.lin@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Feng Tang <feng.tang@...el.com>,
	Tomoya MORINAGA <tomoya.rohm@...il.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH RFT 2/2] gpio: gpio-pch: Use spinlock for register access
 protection

gpio_chip.can_sleep is 0, but current code uses mutex in pch_gpio_set
pch_gpio_get and pch_gpio_direction_input functions.
Thus those functions are not callable from interrupt context.
This patch converts mutex into spinlock.

Signed-off-by: Axel Lin <axel.lin@...il.com>
---
 drivers/gpio/gpio-pch.c |   22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/gpio/gpio-pch.c b/drivers/gpio/gpio-pch.c
index 139ad3e..4ad0c4f 100644
--- a/drivers/gpio/gpio-pch.c
+++ b/drivers/gpio/gpio-pch.c
@@ -92,9 +92,7 @@ struct pch_gpio_reg_data {
  * @lock:			Used for register access protection
  * @irq_base:		Save base of IRQ number for interrupt
  * @ioh:		IOH ID
- * @spinlock:		Used for register access protection in
- *				interrupt context pch_irq_mask,
- *				pch_irq_unmask and pch_irq_type;
+ * @spinlock:		Used for register access protection
  */
 struct pch_gpio {
 	void __iomem *base;
@@ -102,7 +100,6 @@ struct pch_gpio {
 	struct device *dev;
 	struct gpio_chip gpio;
 	struct pch_gpio_reg_data pch_gpio_reg;
-	struct mutex lock;
 	int irq_base;
 	enum pch_type_t ioh;
 	spinlock_t spinlock;
@@ -112,8 +109,9 @@ static void pch_gpio_set(struct gpio_chip *gpio, unsigned nr, int val)
 {
 	u32 reg_val;
 	struct pch_gpio *chip =	container_of(gpio, struct pch_gpio, gpio);
+	unsigned long flags;
 
-	mutex_lock(&chip->lock);
+	spin_lock_irqsave(&chip->spinlock, flags);
 	reg_val = ioread32(&chip->reg->po);
 	if (val)
 		reg_val |= (1 << nr);
@@ -121,7 +119,7 @@ static void pch_gpio_set(struct gpio_chip *gpio, unsigned nr, int val)
 		reg_val &= ~(1 << nr);
 
 	iowrite32(reg_val, &chip->reg->po);
-	mutex_unlock(&chip->lock);
+	spin_unlock_irqrestore(&chip->spinlock, flags);
 }
 
 static int pch_gpio_get(struct gpio_chip *gpio, unsigned nr)
@@ -137,8 +135,9 @@ static int pch_gpio_direction_output(struct gpio_chip *gpio, unsigned nr,
 	struct pch_gpio *chip =	container_of(gpio, struct pch_gpio, gpio);
 	u32 pm;
 	u32 reg_val;
+	unsigned long flags;
 
-	mutex_lock(&chip->lock);
+	spin_lock_irqsave(&chip->spinlock, flags);
 	pm = ioread32(&chip->reg->pm) & ((1 << gpio_pins[chip->ioh]) - 1);
 	pm |= (1 << nr);
 	iowrite32(pm, &chip->reg->pm);
@@ -149,8 +148,7 @@ static int pch_gpio_direction_output(struct gpio_chip *gpio, unsigned nr,
 	else
 		reg_val &= ~(1 << nr);
 	iowrite32(reg_val, &chip->reg->po);
-
-	mutex_unlock(&chip->lock);
+	spin_unlock_irqrestore(&chip->spinlock, flags);
 
 	return 0;
 }
@@ -159,12 +157,13 @@ static int pch_gpio_direction_input(struct gpio_chip *gpio, unsigned nr)
 {
 	struct pch_gpio *chip =	container_of(gpio, struct pch_gpio, gpio);
 	u32 pm;
+	unsigned long flags;
 
-	mutex_lock(&chip->lock);
+	spin_lock_irqsave(&chip->spinlock, flags);
 	pm = ioread32(&chip->reg->pm) & ((1 << gpio_pins[chip->ioh]) - 1);
 	pm &= ~(1 << nr);
 	iowrite32(pm, &chip->reg->pm);
-	mutex_unlock(&chip->lock);
+	spin_unlock_irqrestore(&chip->spinlock, flags);
 
 	return 0;
 }
@@ -387,7 +386,6 @@ static int __devinit pch_gpio_probe(struct pci_dev *pdev,
 
 	chip->reg = chip->base;
 	pci_set_drvdata(pdev, chip);
-	mutex_init(&chip->lock);
 	spin_lock_init(&chip->spinlock);
 	pch_gpio_setup(chip);
 	ret = gpiochip_add(&chip->gpio);
-- 
1.7.9.5



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