Re: [PATCH v2 7/9] gpio: 104-idi-48: make use of raw_spinlock variants
From: William Breathitt Gray <hidden>
Date: 2017-03-22 12:51:31
Also in:
linux-gpio, lkml
On Tue, Mar 21, 2017 at 05:43:07PM -0500, Julia Cartwright wrote:
The 104-idi-48 gpio driver currently implements an irq_chip for handling interrupts; due to how irq_chip handling is done, it's necessary for the irq_chip methods to be invoked from hardirq context, even on a a real-time kernel. Because the spinlock_t type becomes a "sleeping" spinlock w/ RT kernels, it is not suitable to be used with irq_chips. A quick audit of the operations under the lock reveal that they do only minimal, bounded work, and are therefore safe to do under a raw spinlock. Signed-off-by: Julia Cartwright <redacted>
Hi Julia, This driver also uses a second spinlock_t, called ack_lock, to prevent reentrance into the idi_48_irq_handler function. Should ack_lock also be implemented as a raw_spinlock_t? Thanks, William Breathitt Gray
quoted hunk ↗ jump to hunk
--- New patch as of v2 of series. drivers/gpio/gpio-104-idi-48.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-)diff --git a/drivers/gpio/gpio-104-idi-48.c b/drivers/gpio/gpio-104-idi-48.c index 568375a7ebc2..337c048168d8 100644 --- a/drivers/gpio/gpio-104-idi-48.c +++ b/drivers/gpio/gpio-104-idi-48.c@@ -51,7 +51,7 @@ MODULE_PARM_DESC(irq, "ACCES 104-IDI-48 interrupt line numbers"); */struct idi_48_gpio { struct gpio_chip chip; - spinlock_t lock; + raw_spinlock_t lock; spinlock_t ack_lock; unsigned char irq_mask[6]; unsigned base;@@ -112,11 +112,12 @@ static void idi_48_irq_mask(struct irq_data *data)if (!idi48gpio->irq_mask[boundary]) { idi48gpio->cos_enb &= ~BIT(boundary); - spin_lock_irqsave(&idi48gpio->lock, flags); + raw_spin_lock_irqsave(&idi48gpio->lock, flags); outb(idi48gpio->cos_enb, idi48gpio->base + 7); - spin_unlock_irqrestore(&idi48gpio->lock, flags); + raw_spin_unlock_irqrestore(&idi48gpio->lock, + flags); } return;@@ -145,11 +146,12 @@ static void idi_48_irq_unmask(struct irq_data *data)if (!prev_irq_mask) { idi48gpio->cos_enb |= BIT(boundary); - spin_lock_irqsave(&idi48gpio->lock, flags); + raw_spin_lock_irqsave(&idi48gpio->lock, flags); outb(idi48gpio->cos_enb, idi48gpio->base + 7); - spin_unlock_irqrestore(&idi48gpio->lock, flags); + raw_spin_unlock_irqrestore(&idi48gpio->lock, + flags); } return;@@ -186,11 +188,11 @@ static irqreturn_t idi_48_irq_handler(int irq, void *dev_id)spin_lock(&idi48gpio->ack_lock); - spin_lock(&idi48gpio->lock); + raw_spin_lock(&idi48gpio->lock); cos_status = inb(idi48gpio->base + 7); - spin_unlock(&idi48gpio->lock); + raw_spin_unlock(&idi48gpio->lock); /* IRQ Status (bit 6) is active low (0 = IRQ generated by device) */ if (cos_status & BIT(6)) {@@ -256,7 +258,7 @@ static int idi_48_probe(struct device *dev, unsigned int id)idi48gpio->chip.get = idi_48_gpio_get; idi48gpio->base = base[id]; - spin_lock_init(&idi48gpio->lock); + raw_spin_lock_init(&idi48gpio->lock); spin_lock_init(&idi48gpio->ack_lock); err = devm_gpiochip_add_data(dev, &idi48gpio->chip, idi48gpio); -- 2.12.0