| From c69e65cfa2f434730f63867a12139f3fbe6fc49e Mon Sep 17 00:00:00 2001 |
| From: Lukas Wunner <lukas@wunner.de> |
| Date: Sat, 27 Oct 2018 10:15:33 +0200 |
| Subject: pinctrl: bcm2835: Use raw spinlock for RT compatibility |
| |
| [ Upstream commit 3c7b30f704b6f5e53eed6bf89cf2c8d1b38b02c0 ] |
| |
| The BCM2835 pinctrl driver acquires a spinlock in its ->irq_enable, |
| ->irq_disable and ->irq_set_type callbacks. Spinlocks become sleeping |
| locks with CONFIG_PREEMPT_RT_FULL=y, therefore invocation of one of the |
| callbacks in atomic context may cause a hard lockup if at least two GPIO |
| pins in the same bank are used as interrupts. The issue doesn't occur |
| with just a single interrupt pin per bank because the lock is never |
| contended. I'm experiencing such lockups with GPIO 8 and 28 used as |
| level-triggered interrupts, i.e. with ->irq_disable being invoked on |
| reception of every IRQ. |
| |
| The critical section protected by the spinlock is very small (one bitop |
| and one RMW of an MMIO register), hence converting to a raw spinlock |
| seems a better trade-off than converting the driver to threaded IRQ |
| handling (which would increase latency to handle an interrupt). |
| |
| Cc: Mathias Duckeck <m.duckeck@kunbus.de> |
| Signed-off-by: Lukas Wunner <lukas@wunner.de> |
| Acked-by: Julia Cartwright <julia@ni.com> |
| Signed-off-by: Linus Walleij <linus.walleij@linaro.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| drivers/pinctrl/bcm/pinctrl-bcm2835.c | 16 ++++++++-------- |
| 1 file changed, 8 insertions(+), 8 deletions(-) |
| |
| diff --git a/drivers/pinctrl/bcm/pinctrl-bcm2835.c b/drivers/pinctrl/bcm/pinctrl-bcm2835.c |
| index ff782445dfb7..e72bf2502eca 100644 |
| --- a/drivers/pinctrl/bcm/pinctrl-bcm2835.c |
| +++ b/drivers/pinctrl/bcm/pinctrl-bcm2835.c |
| @@ -92,7 +92,7 @@ struct bcm2835_pinctrl { |
| struct gpio_chip gpio_chip; |
| struct pinctrl_gpio_range gpio_range; |
| |
| - spinlock_t irq_lock[BCM2835_NUM_BANKS]; |
| + raw_spinlock_t irq_lock[BCM2835_NUM_BANKS]; |
| }; |
| |
| /* pins are just named GPIO0..GPIO53 */ |
| @@ -471,10 +471,10 @@ static void bcm2835_gpio_irq_enable(struct irq_data *data) |
| unsigned bank = GPIO_REG_OFFSET(gpio); |
| unsigned long flags; |
| |
| - spin_lock_irqsave(&pc->irq_lock[bank], flags); |
| + raw_spin_lock_irqsave(&pc->irq_lock[bank], flags); |
| set_bit(offset, &pc->enabled_irq_map[bank]); |
| bcm2835_gpio_irq_config(pc, gpio, true); |
| - spin_unlock_irqrestore(&pc->irq_lock[bank], flags); |
| + raw_spin_unlock_irqrestore(&pc->irq_lock[bank], flags); |
| } |
| |
| static void bcm2835_gpio_irq_disable(struct irq_data *data) |
| @@ -486,12 +486,12 @@ static void bcm2835_gpio_irq_disable(struct irq_data *data) |
| unsigned bank = GPIO_REG_OFFSET(gpio); |
| unsigned long flags; |
| |
| - spin_lock_irqsave(&pc->irq_lock[bank], flags); |
| + raw_spin_lock_irqsave(&pc->irq_lock[bank], flags); |
| bcm2835_gpio_irq_config(pc, gpio, false); |
| /* Clear events that were latched prior to clearing event sources */ |
| bcm2835_gpio_set_bit(pc, GPEDS0, gpio); |
| clear_bit(offset, &pc->enabled_irq_map[bank]); |
| - spin_unlock_irqrestore(&pc->irq_lock[bank], flags); |
| + raw_spin_unlock_irqrestore(&pc->irq_lock[bank], flags); |
| } |
| |
| static int __bcm2835_gpio_irq_set_type_disabled(struct bcm2835_pinctrl *pc, |
| @@ -594,7 +594,7 @@ static int bcm2835_gpio_irq_set_type(struct irq_data *data, unsigned int type) |
| unsigned long flags; |
| int ret; |
| |
| - spin_lock_irqsave(&pc->irq_lock[bank], flags); |
| + raw_spin_lock_irqsave(&pc->irq_lock[bank], flags); |
| |
| if (test_bit(offset, &pc->enabled_irq_map[bank])) |
| ret = __bcm2835_gpio_irq_set_type_enabled(pc, gpio, type); |
| @@ -606,7 +606,7 @@ static int bcm2835_gpio_irq_set_type(struct irq_data *data, unsigned int type) |
| else |
| irq_set_handler_locked(data, handle_level_irq); |
| |
| - spin_unlock_irqrestore(&pc->irq_lock[bank], flags); |
| + raw_spin_unlock_irqrestore(&pc->irq_lock[bank], flags); |
| |
| return ret; |
| } |
| @@ -1021,7 +1021,7 @@ static int bcm2835_pinctrl_probe(struct platform_device *pdev) |
| for_each_set_bit(offset, &events, 32) |
| bcm2835_gpio_wr(pc, GPEDS0 + i * 4, BIT(offset)); |
| |
| - spin_lock_init(&pc->irq_lock[i]); |
| + raw_spin_lock_init(&pc->irq_lock[i]); |
| } |
| |
| err = gpiochip_add_data(&pc->gpio_chip, pc); |
| -- |
| 2.19.1 |
| |