From d9ff0eb9ca4b00ce2fbf9ede1e99681f05c0bc91 Mon Sep 17 00:00:00 2001 From: Youngmin Nam Date: Tue, 9 Feb 2016 00:49:28 +0900 Subject: [PATCH] pinctrl: samsung: fix SMP race condition Previously, samsung_gpio_drection_in/output function were not covered with a 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. Cc: stable@vger.kernel.org Signed-off-by: Youngmin Nam Acked-by: Tomasz Figa Signed-off-by: Linus Walleij --- 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 f67b1e958589..5cc97f85db02 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; } /* -- GitLab