From: Lukas Wunner Date: Sat, 27 Oct 2018 08:15:33 +0000 (+0200) Subject: pinctrl: bcm2835: Use raw spinlock for RT compatibility X-Git-Tag: v4.19.21~303 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=9d9fcc11b860039d2e28497c27e4418e0a9eaadd;p=platform%2Fkernel%2Flinux-rpi.git 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 Signed-off-by: Lukas Wunner Acked-by: Julia Cartwright Signed-off-by: Linus Walleij Signed-off-by: Sasha Levin --- diff --git a/drivers/pinctrl/bcm/pinctrl-bcm2835.c b/drivers/pinctrl/bcm/pinctrl-bcm2835.c index fa53091..08925d2 100644 --- a/drivers/pinctrl/bcm/pinctrl-bcm2835.c +++ b/drivers/pinctrl/bcm/pinctrl-bcm2835.c @@ -90,7 +90,7 @@ 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 */ @@ -461,10 +461,10 @@ 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) @@ -476,12 +476,12 @@ 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, @@ -584,7 +584,7 @@ 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); @@ -596,7 +596,7 @@ 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; } @@ -1047,7 +1047,7 @@ 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);