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

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

[Julia Cartwright]

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

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

[William Breathitt Gray]

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 <julia@ni.com>

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

>---
>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
>

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

[Julia Cartwright]

On Wed, Mar 22, 2017 at 08:44:14AM -0400, William Breathitt Gray wrote:
> 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 <julia@ni.com>
> 
> 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?

I saw this lock, and I don't even understand it's purpose.

However, I think I convinced myself that it's harmless.  Why?  It's only
ever acquired in a handler registered with request_irq(), which, on RT,
is invoked in a context which can sleep.

Thanks for taking a closer look!

   Julia

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

[Linus Walleij]

On Wed, Mar 22, 2017 at 1:44 PM, William Breathitt Gray
<vilhelm.gray@gmail.com> wrote:
> 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 <julia@ni.com>
>
> 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?

Hm, can I apply this one patch or not?

Linus Walleij

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

[William Breathitt Gray]

On Tue, Mar 28, 2017 at 11:11:59AM +0200, Linus Walleij wrote:
>On Wed, Mar 22, 2017 at 1:44 PM, William Breathitt Gray
><vilhelm.gray@gmail.com> wrote:
>> 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 <julia@ni.com>
>>
>> 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?
>
>Hm, can I apply this one patch or not?
>
>Linus Walleij

Oops, sorry for missing this reply. Julia is correct that ack_lock does
not need to be implemented as raw_spinlock_t. For reference, ack_lock is
used to prevent a race condition on the device hardware itself related
to how the 104-IDI-48 acknowledges IRQ (check out the commit description
for it for a more in-depth explanation if you're curious).

Long story short: Julia's patch is prefectly acceptable as is.

Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>

William Breathitt Gray

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

[Linus Walleij]

On Tue, Mar 21, 2017 at 11:43 PM, Julia Cartwright <julia@ni.com> 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 <julia@ni.com>
> ---
> New patch as of v2 of series.

Patch applied with William's ACK.

Yours,
Linus Walleij

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

[Julia Cartwright]

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

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

[William Breathitt Gray]

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
>

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

[Linus Walleij]

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

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

[Julia Cartwright]

The pci-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-pci-idio-16.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/gpio/gpio-pci-idio-16.c b/drivers/gpio/gpio-pci-idio-16.c
index 269ab628634b..7de4f6a2cb49 100644
--- a/drivers/gpio/gpio-pci-idio-16.c
+++ b/drivers/gpio/gpio-pci-idio-16.c
@@ -59,7 +59,7 @@ struct idio_16_gpio_reg {
  */
 struct idio_16_gpio {
 	struct gpio_chip chip;
-	spinlock_t lock;
+	raw_spinlock_t lock;
 	struct idio_16_gpio_reg __iomem *reg;
 	unsigned long irq_mask;
 };
@@ -121,7 +121,7 @@ static void idio_16_gpio_set(struct gpio_chip *chip, unsigned int offset,
 	} else
 		base = &idio16gpio->reg->out0_7;
 
-	spin_lock_irqsave(&idio16gpio->lock, flags);
+	raw_spin_lock_irqsave(&idio16gpio->lock, flags);
 
 	if (value)
 		out_state = ioread8(base) | mask;
@@ -130,7 +130,7 @@ static void idio_16_gpio_set(struct gpio_chip *chip, unsigned int offset,
 
 	iowrite8(out_state, 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,
@@ -140,7 +140,7 @@ static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
 	unsigned long flags;
 	unsigned int out_state;
 
-	spin_lock_irqsave(&idio16gpio->lock, flags);
+	raw_spin_lock_irqsave(&idio16gpio->lock, flags);
 
 	/* process output lines 0-7 */
 	if (*mask & 0xFF) {
@@ -160,7 +160,7 @@ static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
 		iowrite8(out_state, &idio16gpio->reg->out8_15);
 	}
 
-	spin_unlock_irqrestore(&idio16gpio->lock, flags);
+	raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
 }
 
 static void idio_16_irq_ack(struct irq_data *data)
@@ -177,11 +177,11 @@ 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);
 
 		iowrite8(0, &idio16gpio->reg->irq_ctl);
 
-		spin_unlock_irqrestore(&idio16gpio->lock, flags);
+		raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
 	}
 }
 
@@ -196,11 +196,11 @@ 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);
 
 		ioread8(&idio16gpio->reg->irq_ctl);
 
-		spin_unlock_irqrestore(&idio16gpio->lock, flags);
+		raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
 	}
 }
 
@@ -229,11 +229,11 @@ static irqreturn_t idio_16_irq_handler(int irq, void *dev_id)
 	struct gpio_chip *const chip = &idio16gpio->chip;
 	int gpio;
 
-	spin_lock(&idio16gpio->lock);
+	raw_spin_lock(&idio16gpio->lock);
 
 	irq_status = ioread8(&idio16gpio->reg->irq_status);
 
-	spin_unlock(&idio16gpio->lock);
+	raw_spin_unlock(&idio16gpio->lock);
 
 	/* Make sure our device generated IRQ */
 	if (!(irq_status & 0x3) || !(irq_status & 0x4))
@@ -242,12 +242,12 @@ 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);
 
 	/* Clear interrupt */
 	iowrite8(0, &idio16gpio->reg->in0_7);
 
-	spin_unlock(&idio16gpio->lock);
+	raw_spin_unlock(&idio16gpio->lock);
 
 	return IRQ_HANDLED;
 }
@@ -302,7 +302,7 @@ static int idio_16_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	idio16gpio->chip.set = idio_16_gpio_set;
 	idio16gpio->chip.set_multiple = idio_16_gpio_set_multiple;
 
-	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

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

[William Breathitt Gray]

On Tue, Mar 21, 2017 at 05:43:09PM -0500, Julia Cartwright wrote:
>The pci-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-pci-idio-16.c | 28 ++++++++++++++--------------
> 1 file changed, 14 insertions(+), 14 deletions(-)
>
>diff --git a/drivers/gpio/gpio-pci-idio-16.c b/drivers/gpio/gpio-pci-idio-16.c
>index 269ab628634b..7de4f6a2cb49 100644
>--- a/drivers/gpio/gpio-pci-idio-16.c
>+++ b/drivers/gpio/gpio-pci-idio-16.c
>@@ -59,7 +59,7 @@ struct idio_16_gpio_reg {
>  */
> struct idio_16_gpio {
> 	struct gpio_chip chip;
>-	spinlock_t lock;
>+	raw_spinlock_t lock;
> 	struct idio_16_gpio_reg __iomem *reg;
> 	unsigned long irq_mask;
> };
>@@ -121,7 +121,7 @@ static void idio_16_gpio_set(struct gpio_chip *chip, unsigned int offset,
> 	} else
> 		base = &idio16gpio->reg->out0_7;
> 
>-	spin_lock_irqsave(&idio16gpio->lock, flags);
>+	raw_spin_lock_irqsave(&idio16gpio->lock, flags);
> 
> 	if (value)
> 		out_state = ioread8(base) | mask;
>@@ -130,7 +130,7 @@ static void idio_16_gpio_set(struct gpio_chip *chip, unsigned int offset,
> 
> 	iowrite8(out_state, 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,
>@@ -140,7 +140,7 @@ static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
> 	unsigned long flags;
> 	unsigned int out_state;
> 
>-	spin_lock_irqsave(&idio16gpio->lock, flags);
>+	raw_spin_lock_irqsave(&idio16gpio->lock, flags);
> 
> 	/* process output lines 0-7 */
> 	if (*mask & 0xFF) {
>@@ -160,7 +160,7 @@ static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
> 		iowrite8(out_state, &idio16gpio->reg->out8_15);
> 	}
> 
>-	spin_unlock_irqrestore(&idio16gpio->lock, flags);
>+	raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
> }
> 
> static void idio_16_irq_ack(struct irq_data *data)
>@@ -177,11 +177,11 @@ 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);
> 
> 		iowrite8(0, &idio16gpio->reg->irq_ctl);
> 
>-		spin_unlock_irqrestore(&idio16gpio->lock, flags);
>+		raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
> 	}
> }
> 
>@@ -196,11 +196,11 @@ 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);
> 
> 		ioread8(&idio16gpio->reg->irq_ctl);
> 
>-		spin_unlock_irqrestore(&idio16gpio->lock, flags);
>+		raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
> 	}
> }
> 
>@@ -229,11 +229,11 @@ static irqreturn_t idio_16_irq_handler(int irq, void *dev_id)
> 	struct gpio_chip *const chip = &idio16gpio->chip;
> 	int gpio;
> 
>-	spin_lock(&idio16gpio->lock);
>+	raw_spin_lock(&idio16gpio->lock);
> 
> 	irq_status = ioread8(&idio16gpio->reg->irq_status);
> 
>-	spin_unlock(&idio16gpio->lock);
>+	raw_spin_unlock(&idio16gpio->lock);
> 
> 	/* Make sure our device generated IRQ */
> 	if (!(irq_status & 0x3) || !(irq_status & 0x4))
>@@ -242,12 +242,12 @@ 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);
> 
> 	/* Clear interrupt */
> 	iowrite8(0, &idio16gpio->reg->in0_7);
> 
>-	spin_unlock(&idio16gpio->lock);
>+	raw_spin_unlock(&idio16gpio->lock);
> 
> 	return IRQ_HANDLED;
> }
>@@ -302,7 +302,7 @@ static int idio_16_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> 	idio16gpio->chip.set = idio_16_gpio_set;
> 	idio16gpio->chip.set_multiple = idio_16_gpio_set_multiple;
> 
>-	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
>

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

[Linus Walleij]

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

> The pci-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 with William's ACK.

Yours,
Linus Walleij