Re: [PATCH v3] pinctrl: samsung: Fixes samsung_gpio_direction_in/output releated with spinlock

[Youngmin Nam <ym0914@gmail.com>]

Hello tomasz and linus,

I got to know that below my v3 patch has build error now.

I will fix it and resend.

Thanks.

On 2016년 02월 08일 23:54, Youngmin Nam wrote:
> 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@gmail.com>
> Acked-by: Tomasz Figa <tomasz.figa@gmail.com>
> ---
>  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..38142c2 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 = 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);
>  }
>  
> @@ -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 = 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;
>  }
>  
>  /*
>