gpio: ws16c48: make use of raw_spinlock variants

The ws16c48 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>
Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-ws16c48.c

@@ -51,7 +51,7 @@ struct ws16c48_gpio {
 	struct gpio_chip chip;
 	unsigned char io_state[6];
 	unsigned char out_state[6];
-	spinlock_t lock;
+	raw_spinlock_t lock;
 	unsigned long irq_mask;
 	unsigned long flow_mask;
 	unsigned base;
@@ -73,13 +73,13 @@ static int ws16c48_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
 	const unsigned mask = BIT(offset % 8);
 	unsigned long flags;
 
-	spin_lock_irqsave(&ws16c48gpio->lock, flags);
+	raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);
 
 	ws16c48gpio->io_state[port] |= mask;
 	ws16c48gpio->out_state[port] &= ~mask;
 	outb(ws16c48gpio->out_state[port], ws16c48gpio->base + port);
 
-	spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 
 	return 0;
 }
@@ -92,7 +92,7 @@ static int ws16c48_gpio_direction_output(struct gpio_chip *chip,
 	const unsigned mask = BIT(offset % 8);
 	unsigned long flags;
 
-	spin_lock_irqsave(&ws16c48gpio->lock, flags);
+	raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);
 
 	ws16c48gpio->io_state[port] &= ~mask;
 	if (value)
@@ -101,7 +101,7 @@ static int ws16c48_gpio_direction_output(struct gpio_chip *chip,
 		ws16c48gpio->out_state[port] &= ~mask;
 	outb(ws16c48gpio->out_state[port], ws16c48gpio->base + port);
 
-	spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 
 	return 0;
 }
@@ -114,17 +114,17 @@ static int ws16c48_gpio_get(struct gpio_chip *chip, unsigned offset)
 	unsigned long flags;
 	unsigned port_state;
 
-	spin_lock_irqsave(&ws16c48gpio->lock, flags);
+	raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);
 
 	/* ensure that GPIO is set for input */
 	if (!(ws16c48gpio->io_state[port] & mask)) {
-		spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+		raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 		return -EINVAL;
 	}
 
 	port_state = inb(ws16c48gpio->base + port);
 
-	spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 
 	return !!(port_state & mask);
 }
@@ -136,11 +136,11 @@ static void ws16c48_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
 	const unsigned mask = BIT(offset % 8);
 	unsigned long flags;
 
-	spin_lock_irqsave(&ws16c48gpio->lock, flags);
+	raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);
 
 	/* ensure that GPIO is set for output */
 	if (ws16c48gpio->io_state[port] & mask) {
-		spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+		raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 		return;
 	}
 
@@ -150,7 +150,7 @@ static void ws16c48_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
 		ws16c48gpio->out_state[port] &= ~mask;
 	outb(ws16c48gpio->out_state[port], ws16c48gpio->base + port);
 
-	spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 }
 
 static void ws16c48_gpio_set_multiple(struct gpio_chip *chip,
@@ -178,14 +178,14 @@ static void ws16c48_gpio_set_multiple(struct gpio_chip *chip,
 		iomask = mask[BIT_WORD(i)] & ~ws16c48gpio->io_state[port];
 		bitmask = iomask & bits[BIT_WORD(i)];
 
-		spin_lock_irqsave(&ws16c48gpio->lock, flags);
+		raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);
 
 		/* update output state data and set device gpio register */
 		ws16c48gpio->out_state[port] &= ~iomask;
 		ws16c48gpio->out_state[port] |= bitmask;
 		outb(ws16c48gpio->out_state[port], ws16c48gpio->base + port);
 
-		spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+		raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 
 		/* prepare for next gpio register set */
 		mask[BIT_WORD(i)] >>= gpio_reg_size;
@@ -207,7 +207,7 @@ static void ws16c48_irq_ack(struct irq_data *data)
 	if (port > 2)
 		return;
 
-	spin_lock_irqsave(&ws16c48gpio->lock, flags);
+	raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);
 
 	port_state = ws16c48gpio->irq_mask >> (8*port);
 
@@ -216,7 +216,7 @@ static void ws16c48_irq_ack(struct irq_data *data)
 	outb(port_state | mask, ws16c48gpio->base + 8 + port);
 	outb(0xC0, ws16c48gpio->base + 7);
 
-	spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 }
 
 static void ws16c48_irq_mask(struct irq_data *data)
@@ -232,7 +232,7 @@ static void ws16c48_irq_mask(struct irq_data *data)
 	if (port > 2)
 		return;
 
-	spin_lock_irqsave(&ws16c48gpio->lock, flags);
+	raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);
 
 	ws16c48gpio->irq_mask &= ~mask;
 
@@ -240,7 +240,7 @@ static void ws16c48_irq_mask(struct irq_data *data)
 	outb(ws16c48gpio->irq_mask >> (8*port), ws16c48gpio->base + 8 + port);
 	outb(0xC0, ws16c48gpio->base + 7);
 
-	spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 }
 
 static void ws16c48_irq_unmask(struct irq_data *data)
@@ -256,7 +256,7 @@ static void ws16c48_irq_unmask(struct irq_data *data)
 	if (port > 2)
 		return;
 
-	spin_lock_irqsave(&ws16c48gpio->lock, flags);
+	raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);
 
 	ws16c48gpio->irq_mask |= mask;
 
@@ -264,7 +264,7 @@ static void ws16c48_irq_unmask(struct irq_data *data)
 	outb(ws16c48gpio->irq_mask >> (8*port), ws16c48gpio->base + 8 + port);
 	outb(0xC0, ws16c48gpio->base + 7);
 
-	spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 }
 
 static int ws16c48_irq_set_type(struct irq_data *data, unsigned flow_type)
@@ -280,7 +280,7 @@ static int ws16c48_irq_set_type(struct irq_data *data, unsigned flow_type)
 	if (port > 2)
 		return -EINVAL;
 
-	spin_lock_irqsave(&ws16c48gpio->lock, flags);
+	raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);
 
 	switch (flow_type) {
 	case IRQ_TYPE_NONE:
@@ -292,7 +292,7 @@ static int ws16c48_irq_set_type(struct irq_data *data, unsigned flow_type)
 		ws16c48gpio->flow_mask &= ~mask;
 		break;
 	default:
-		spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+		raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 		return -EINVAL;
 	}
 
@@ -300,7 +300,7 @@ static int ws16c48_irq_set_type(struct irq_data *data, unsigned flow_type)
 	outb(ws16c48gpio->flow_mask >> (8*port), ws16c48gpio->base + 8 + port);
 	outb(0xC0, ws16c48gpio->base + 7);
 
-	spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 
 	return 0;
 }
@@ -387,7 +387,7 @@ static int ws16c48_probe(struct device *dev, unsigned int id)
 	ws16c48gpio->chip.set_multiple = ws16c48_gpio_set_multiple;
 	ws16c48gpio->base = base[id];
 
-	spin_lock_init(&ws16c48gpio->lock);
+	raw_spin_lock_init(&ws16c48gpio->lock);
 
 	err = devm_gpiochip_add_data(dev, &ws16c48gpio->chip, ws16c48gpio);
 	if (err) {