linux-kernel - Re: [PATCH] pch_gpio: transform mutex into spinlock

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Date:	Mon, 27 Jun 2011 16:47:22 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Alexander Stein <alexander.stein@...tec-electronic.com>
Cc:	linux-kernel@...r.kernel.org,
	Tomoya MORINAGA <tomoya-linux@....okisemi.com>
Subject: Re: [PATCH] pch_gpio: transform mutex into spinlock

On Tue, Jun 21, 2011 at 04:17:27PM +0200, Alexander Stein wrote:
> gpio_chip.can_sleep is 0, but gpio_set_value & friends lock a mutex. Thus
> those functions are not callable from interrupt context.
> Changing mutex into spinlock.
> 
> Signed-off-by: Alexander Stein <alexander.stein@...tec-electronic.com>

Tomoya, what do you think of this patch?

> ---
> I just noticed that the patch introduced at
> http://marc.info/?l=linux-kernel&m=130863151431202&w=2
> also added a spinlock. I think those two spinlock can be merged into one.
> 
>  drivers/gpio/pch_gpio.c |   19 +++++++++++--------
>  1 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpio/pch_gpio.c b/drivers/gpio/pch_gpio.c
> index 36919e7..262c200 100644
> --- a/drivers/gpio/pch_gpio.c
> +++ b/drivers/gpio/pch_gpio.c
> @@ -62,15 +62,16 @@ struct pch_gpio {
>  	struct device *dev;
>  	struct gpio_chip gpio;
>  	struct pch_gpio_reg_data pch_gpio_reg;
> -	struct mutex lock;
> +	struct spinlock lock;
>  };
>  
>  static void pch_gpio_set(struct gpio_chip *gpio, unsigned nr, int val)
>  {
>  	u32 reg_val;
> +	unsigned long flags;
>  	struct pch_gpio *chip =	container_of(gpio, struct pch_gpio, gpio);
>  
> -	mutex_lock(&chip->lock);
> +	spin_lock_irqsave(&chip->lock, flags);
>  	reg_val = ioread32(&chip->reg->po);
>  	if (val)
>  		reg_val |= (1 << nr);
> @@ -78,7 +79,7 @@ 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->lock, flags);
>  }
>  
>  static int pch_gpio_get(struct gpio_chip *gpio, unsigned nr)
> @@ -94,8 +95,9 @@ 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->lock, flags);
>  	pm = ioread32(&chip->reg->pm) & PCH_GPIO_ALL_PINS;
>  	pm |= (1 << nr);
>  	iowrite32(pm, &chip->reg->pm);
> @@ -107,7 +109,7 @@ static int pch_gpio_direction_output(struct gpio_chip *gpio, unsigned nr,
>  		reg_val &= ~(1 << nr);
>  	iowrite32(reg_val, &chip->reg->po);
>  
> -	mutex_unlock(&chip->lock);
> +	spin_unlock_irqrestore(&chip->lock, flags);
>  
>  	return 0;
>  }
> @@ -116,12 +118,13 @@ 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->lock, flags);
>  	pm = ioread32(&chip->reg->pm) & PCH_GPIO_ALL_PINS; /*bits 0-11*/
>  	pm &= ~(1 << nr);
>  	iowrite32(pm, &chip->reg->pm);
> -	mutex_unlock(&chip->lock);
> +	spin_unlock_irqrestore(&chip->lock, flags);
>  
>  	return 0;
>  }
> @@ -194,7 +197,7 @@ 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->lock);
>  	pch_gpio_setup(chip);
>  	ret = gpiochip_add(&chip->gpio);
>  	if (ret) {
> -- 
> 1.7.3.4
> 
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