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[PATCH v2 8/9] gpio: 104-idio-16: make use of raw_spinlock variants

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  [PATCH v2 8/9] gpio: 104-idio-16: make use of raw_spinlock variants Julia Cartwright <julia@ni.com> - 2017-03-22 00:50 +0100
    Re: [PATCH v2 8/9] gpio: 104-idio-16: make use of raw_spinlock  variants William Breathitt Gray <vilhelm.gray@gmail.com> - 2017-03-22 13:50 +0100
    Re: [PATCH v2 8/9] gpio: 104-idio-16: make use of raw_spinlock variants Linus Walleij <linus.walleij@linaro.org> - 2017-03-28 11:20 +0200

#1606092 — [PATCH v2 8/9] gpio: 104-idio-16: make use of raw_spinlock variants

The 104-idio-16 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-idio-16.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/gpio/gpio-104-idio-16.c b/drivers/gpio/gpio-104-idio-16.c
index 7053cf736648..5281e1cedb01 100644
--- a/drivers/gpio/gpio-104-idio-16.c
+++ b/drivers/gpio/gpio-104-idio-16.c
@@ -50,7 +50,7 @@ MODULE_PARM_DESC(irq, "ACCES 104-IDIO-16 interrupt line numbers");
  */
 struct idio_16_gpio {
 	struct gpio_chip chip;
-	spinlock_t lock;
+	raw_spinlock_t lock;
 	unsigned long irq_mask;
 	unsigned base;
 	unsigned out_state;
@@ -99,7 +99,7 @@ static void idio_16_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
 	if (offset > 15)
 		return;
 
-	spin_lock_irqsave(&idio16gpio->lock, flags);
+	raw_spin_lock_irqsave(&idio16gpio->lock, flags);
 
 	if (value)
 		idio16gpio->out_state |= mask;
@@ -111,7 +111,7 @@ static void idio_16_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
 	else
 		outb(idio16gpio->out_state, idio16gpio->base);
 
-	spin_unlock_irqrestore(&idio16gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
 }
 
 static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
@@ -120,7 +120,7 @@ static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
 	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);
 	unsigned long flags;
 
-	spin_lock_irqsave(&idio16gpio->lock, flags);
+	raw_spin_lock_irqsave(&idio16gpio->lock, flags);
 
 	idio16gpio->out_state &= ~*mask;
 	idio16gpio->out_state |= *mask & *bits;
@@ -130,7 +130,7 @@ static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
 	if ((*mask >> 8) & 0xFF)
 		outb(idio16gpio->out_state >> 8, idio16gpio->base + 4);
 
-	spin_unlock_irqrestore(&idio16gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
 }
 
 static void idio_16_irq_ack(struct irq_data *data)
@@ -147,11 +147,11 @@ static void idio_16_irq_mask(struct irq_data *data)
 	idio16gpio->irq_mask &= ~mask;
 
 	if (!idio16gpio->irq_mask) {
-		spin_lock_irqsave(&idio16gpio->lock, flags);
+		raw_spin_lock_irqsave(&idio16gpio->lock, flags);
 
 		outb(0, idio16gpio->base + 2);
 
-		spin_unlock_irqrestore(&idio16gpio->lock, flags);
+		raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
 	}
 }
 
@@ -166,11 +166,11 @@ static void idio_16_irq_unmask(struct irq_data *data)
 	idio16gpio->irq_mask |= mask;
 
 	if (!prev_irq_mask) {
-		spin_lock_irqsave(&idio16gpio->lock, flags);
+		raw_spin_lock_irqsave(&idio16gpio->lock, flags);
 
 		inb(idio16gpio->base + 2);
 
-		spin_unlock_irqrestore(&idio16gpio->lock, flags);
+		raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
 	}
 }
 
@@ -201,11 +201,11 @@ static irqreturn_t idio_16_irq_handler(int irq, void *dev_id)
 	for_each_set_bit(gpio, &idio16gpio->irq_mask, chip->ngpio)
 		generic_handle_irq(irq_find_mapping(chip->irqdomain, gpio));
 
-	spin_lock(&idio16gpio->lock);
+	raw_spin_lock(&idio16gpio->lock);
 
 	outb(0, idio16gpio->base + 1);
 
-	spin_unlock(&idio16gpio->lock);
+	raw_spin_unlock(&idio16gpio->lock);
 
 	return IRQ_HANDLED;
 }
@@ -249,7 +249,7 @@ static int idio_16_probe(struct device *dev, unsigned int id)
 	idio16gpio->base = base[id];
 	idio16gpio->out_state = 0xFFFF;
 
-	spin_lock_init(&idio16gpio->lock);
+	raw_spin_lock_init(&idio16gpio->lock);
 
 	err = devm_gpiochip_add_data(dev, &idio16gpio->chip, idio16gpio);
 	if (err) {
-- 
2.12.0

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#1606432 — Re: [PATCH v2 8/9] gpio: 104-idio-16: make use of raw_spinlock variants

On Tue, Mar 21, 2017 at 05:43:08PM -0500, Julia Cartwright wrote:
>The 104-idio-16 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>

>---
>New patch as of v2 of series.
>
> drivers/gpio/gpio-104-idio-16.c | 24 ++++++++++++------------
> 1 file changed, 12 insertions(+), 12 deletions(-)
>
>diff --git a/drivers/gpio/gpio-104-idio-16.c b/drivers/gpio/gpio-104-idio-16.c
>index 7053cf736648..5281e1cedb01 100644
>--- a/drivers/gpio/gpio-104-idio-16.c
>+++ b/drivers/gpio/gpio-104-idio-16.c
>@@ -50,7 +50,7 @@ MODULE_PARM_DESC(irq, "ACCES 104-IDIO-16 interrupt line numbers");
>  */
> struct idio_16_gpio {
> 	struct gpio_chip chip;
>-	spinlock_t lock;
>+	raw_spinlock_t lock;
> 	unsigned long irq_mask;
> 	unsigned base;
> 	unsigned out_state;
>@@ -99,7 +99,7 @@ static void idio_16_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
> 	if (offset > 15)
> 		return;
> 
>-	spin_lock_irqsave(&idio16gpio->lock, flags);
>+	raw_spin_lock_irqsave(&idio16gpio->lock, flags);
> 
> 	if (value)
> 		idio16gpio->out_state |= mask;
>@@ -111,7 +111,7 @@ static void idio_16_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
> 	else
> 		outb(idio16gpio->out_state, idio16gpio->base);
> 
>-	spin_unlock_irqrestore(&idio16gpio->lock, flags);
>+	raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
> }
> 
> static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
>@@ -120,7 +120,7 @@ static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
> 	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);
> 	unsigned long flags;
> 
>-	spin_lock_irqsave(&idio16gpio->lock, flags);
>+	raw_spin_lock_irqsave(&idio16gpio->lock, flags);
> 
> 	idio16gpio->out_state &= ~*mask;
> 	idio16gpio->out_state |= *mask & *bits;
>@@ -130,7 +130,7 @@ static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
> 	if ((*mask >> 8) & 0xFF)
> 		outb(idio16gpio->out_state >> 8, idio16gpio->base + 4);
> 
>-	spin_unlock_irqrestore(&idio16gpio->lock, flags);
>+	raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
> }
> 
> static void idio_16_irq_ack(struct irq_data *data)
>@@ -147,11 +147,11 @@ static void idio_16_irq_mask(struct irq_data *data)
> 	idio16gpio->irq_mask &= ~mask;
> 
> 	if (!idio16gpio->irq_mask) {
>-		spin_lock_irqsave(&idio16gpio->lock, flags);
>+		raw_spin_lock_irqsave(&idio16gpio->lock, flags);
> 
> 		outb(0, idio16gpio->base + 2);
> 
>-		spin_unlock_irqrestore(&idio16gpio->lock, flags);
>+		raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
> 	}
> }
> 
>@@ -166,11 +166,11 @@ static void idio_16_irq_unmask(struct irq_data *data)
> 	idio16gpio->irq_mask |= mask;
> 
> 	if (!prev_irq_mask) {
>-		spin_lock_irqsave(&idio16gpio->lock, flags);
>+		raw_spin_lock_irqsave(&idio16gpio->lock, flags);
> 
> 		inb(idio16gpio->base + 2);
> 
>-		spin_unlock_irqrestore(&idio16gpio->lock, flags);
>+		raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
> 	}
> }
> 
>@@ -201,11 +201,11 @@ static irqreturn_t idio_16_irq_handler(int irq, void *dev_id)
> 	for_each_set_bit(gpio, &idio16gpio->irq_mask, chip->ngpio)
> 		generic_handle_irq(irq_find_mapping(chip->irqdomain, gpio));
> 
>-	spin_lock(&idio16gpio->lock);
>+	raw_spin_lock(&idio16gpio->lock);
> 
> 	outb(0, idio16gpio->base + 1);
> 
>-	spin_unlock(&idio16gpio->lock);
>+	raw_spin_unlock(&idio16gpio->lock);
> 
> 	return IRQ_HANDLED;
> }
>@@ -249,7 +249,7 @@ static int idio_16_probe(struct device *dev, unsigned int id)
> 	idio16gpio->base = base[id];
> 	idio16gpio->out_state = 0xFFFF;
> 
>-	spin_lock_init(&idio16gpio->lock);
>+	raw_spin_lock_init(&idio16gpio->lock);
> 
> 	err = devm_gpiochip_add_data(dev, &idio16gpio->chip, idio16gpio);
> 	if (err) {
>-- 
>2.12.0
>

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#1610459

On Tue, Mar 21, 2017 at 11:43 PM, Julia Cartwright <julia@ni.com> wrote:

> The 104-idio-16 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.

Patch applied to the GPIO tree with William's ACK.

Yours,
Linus Walleij

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