[PATCH v2 7/9] gpio: 104-idi-48: make use of raw_spinlock variants

Julia Cartwright
2017-03-21T22:43:07Z

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 <julia@ni.com>
---
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